23 June 2026, Volume 39 Issue 3
    

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  • Research Progress in Laser Shock Peening for Nickel-based Single-crystal Superalloys
    LANG Mo, ZHOU Guangni, LUO Sihai, HU Shuang, ZHANG Huailin, LI Yuliang, PENG Ruixiang, HE Weifeng
    China Surface Engineering. 2026, 39(3): 1-19. https://doi.org/10.11933/CSE2026164
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    Nickel-based single-crystal superalloys are widely used in aviation and industrial gas turbine blades owing to their excellent mechanical properties at high temperatures. However, under extreme service conditions, these superalloys are susceptible to fatigue, wear, corrosion, and oxidation damage, which pose significant risks to engine safety. Laser shock peening (LSP) is an advanced surface-strengthening technology that utilizes laser shock waves to induce severe plastic deformation at the surface, alter the microstructure, and introduce compressive residual stress (CRS), thereby enhancing the fatigue resistance and other properties of the alloy. Some studies have investigated the laser shock strengthening of nickel-based single-crystal superalloys for turbine blades. However, there is a notable lack of a systematic summary on this topic. This study begins by examining the technical characteristics of various LSP technologies, including traditional high-energy laser shock, low-energy laser shock without an absorption layer, warm LSP (WLSP), and femtosecond LSP (Fs-LSP). The effects of these technologies on the microstructures and properties of nickel-based single-crystal superalloys are compared, highlighting their respective advantages and disadvantages. This summary revealed that the strengthening effects of various LSP technologies on single-crystal superalloys differ. Ns-LSP and WLSP can achieve millimeter-level strengthening layer depths; LSPwC reaches several hundred micrometers; and Fs-LSP results in depths of tens of micrometers. The strengthening mechanisms of the four LSP processes for nickel-based single-crystal superalloys are distinct. Ns-LSP primarily strengthens by introducing high-density crystal defects and CRS during the shock process. WLSP improves the density, uniformity, and stability of crystal defects. LSPwC not only introduces crystal defects and CRS but also generates in-situ nano-oxide particles that further impede the dislocation motion, enhancing the strengthening effect. Fs-LSP introduces both crystal defects and CRS, and simultaneously builds surface periodic micro-nanostructures, achieving a synergistic optimization of strengthening effect and functional structure. Each of these processes has unique features and provides diverse technical paths for the performance enhancement of single-crystal alloys. Despite the different depths of strengthening layers, the core mechanism of these techniques lies in the large number of crystal defects and CRS introduced by LSP. The large plastic deformation induced by Ns-LSP and WLSP may lead to recrystallization of the single-crystal superalloy during the strengthening/service process, thereby damaging its high-temperature creep performance. Therefore, further research is needed to explore how LSP technology can achieve efficient and high-quality strengthening of single-crystal superalloys, and obtain ideal single-crystal structures. When LSPwC is used to strengthen single-crystal superalloys, the laser directly acts on the alloy surface, leading to surface remelting and oxidation, which in turn reduces the surface quality. Therefore, further research is required to improve the surface quality of the LSPwC-treated single-crystal superalloys and enhance their strengthening effect. The paper also discusses the challenges and difficulties faced in the LSP of nickel-based single-crystal superalloys and offers insights into future development trends. LSP technology has already been commercially applied in other alloy fields, and research has shown that it can improve issues such as fatigue, wear, oxidation, and corrosion in nickel-based single-crystal superalloys. To further advance this technology and expand its market penetration, it should be developed in several directions: composite strengthening process innovation, upgrading of residual stress detection equipment, innovations in equipment manufacturing technology, and the establishment of intelligent processing systems.
  • Research Progress on Preparation of Diamond-like Carbon Films Using Physical Vapor Deposition
    LIU Shuyang, TAO Guanyu, CHEN Hui, ZHANG Yu, DU Jianrong, ZENG Lu, WU Zhenyu
    China Surface Engineering. 2026, 39(3): 20-49. https://doi.org/10.11933/CSE2026072
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    Diamond-like carbon films that exhibit exceptional properties including high hardness, low friction factor, wear resistance, corrosion resistance, and good biocompatibility, making them a valuable tool for coating tools, automotive parts, biomedicine, and other fields. Physical vapor deposition (PVD) is one of the most common techniques used to deposit diamond-like carbon films. However, the characteristics of carbon films produced by different PVD techniques exhibit notable disparities that constrain their applicability in industrial contexts. To address this issues, this study summarizes the research progress in the preparation of diamond-like carbon films using PVD technologies and the current improved technologies that have been developed in response to the poor comprehensive mechanical properties of carbon films caused by large droplets during the deposition of DLC films using CAE technology. These include imposed pulse cathode arc evaporation, filtered cathodic vacuum arc, pulsed laser-induced cathodic vacuum arc, and thermoionic vacuum arc technologies. To address the challenges posed by HiPIMS technology in an Ar atmosphere, such as the inability to effectively ionize the graphite target and the resulting low hardness and density, novel technologies have been developed to enhance the performance of carbon films by modulating the sputtering gas and optimization of the discharge process of the power supply. These techniques include short-pulse HiPIMS, deep oscillation magnetron sputtering, mixed-mode HiPIMS, and bipolar HiPIMS. Using short-pulse HiPIMS, deep oscillation magnetron sputtering, and mixed-mode HiPIMS technologies has been demonstrated to enhance the ionization rate of graphite targets. Furthermore, bipolar HiPIMS improves the efficiency of carbon ion transport. A comparative analysis of the properties, advantages, and disadvantages of DLC films deposited using these techniques was conducted to evaluate their application potential. In addition, research progress on the adhesion, tribological, and multi-factor coupling properties of diamond-like carbon films is summarized. In the following discussion, the efficacy of elemental doping and multilayer composite structures for enhancing the performance of DLC films in diverse service environments is examined. Patterning DLC films with different segmented structures is a novel technique for enhancing the tribological properties of carbon films. The current state of DLC films in engineering applications is introduced, and the structural and performance requirements of DLC films in different application scenarios are summarized. Finally, the new PVD technologies are compared for the above application scenarios. Tool coating represents a prevalent application domain for DLC films. However, the wear of carbon films at elevated temperatures and low bond strength represent pressing challenges to be addressed in the large-scale production and application of DLC tool coatings. In contrast to conventional nitride and carbide ceramic films, DLC films enhance the corrosion resistance and conductivity of metal bipolar plates in fuel cells, indicating their promising application in fuel cell bipolar plate coatings. The preparation of diamond-like carbon films using PVD technology is a promising future path, and the emerging HiPIMS and its improved technology can provide a cost-effective coating solution that is well suited for industrial applications. Nevertheless, there remains a significant disparity between our high-performance DLC film deposition technology and equipment, and advanced international standards. In addition, exploring coupled damage and detection methods in various complex environments is a promising avenue for future research. This study presents a comprehensive review of the development status and trends in diamond-like carbon films prepared using PVD technology aiming to establish a foundation for developing cost-effective, high-performance DLC technologies better suited for industrial applications.
  • Research Advancements in Cold-sprayed Zn and Zn Alloy Coatings
    CONG Shengyi, ZHOU Hongxia
    China Surface Engineering. 2026, 39(3): 50-70. https://doi.org/10.11933/CSE2026165
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    Cold-sprayed Zn coatings have attracted considerable attention as a topic of active research in materials science and surface engineering owing to their superior resistance to corrosion. Thus, techniques based on cold-sprayed Zn coatings have been developed rapidly over the past few decades, with a focus on enhancing their performance and broadening potential areas of application. In this study, we provide an in-depth review of recent works on cold-sprayed Zn coatings to offer a comprehensive summary of advancements in pure Zn, Zn-alloy, and Zn-based composite coatings. First, we examine the microstructure and properties of cold-sprayed pure Zn coatings. Studies have shown that the deposition process results in a unique microstructure characterized by fine grains and high density, which confers excellent initial resistance to corrosion. However, it still needs some improvement in terms of the mechanical properties of the coatings such as their hardness and tensile strength. Research efforts have concentrated on optimizing spraying parameters such as gas pressure and temperature to enhance the density and uniformity of the coatings to improve their overall performance. Secondly, we systematically review the relevant literatures on cold-sprayed Zn coating, Zn-alloy coating, and Zn-ceramic composite coating. The adding elements such as Al, Mg, or Ni can significantly alter the microstructure and properties of Zn coatings. For example, studies have shown that the formation of intermetallic compounds in Zn-Al alloy coating plays a crucial role in enhancing corrosion resistance and mechanical strength. These compounds act as barriers against corrosion and strengthen the coating. In Zn-ceramic composite coating, the incorporation of ceramic particles such as alumina (Al2O3) or titanium dioxide (TiO2) can improve coating’s hardness and wear resistance. A study on Zn-Al2O3 coating found that the wear rate of the coating was significantly reduced under specific tribological test conditions with the addition of a certain proportion of Al2O3 particles. The key findings of these studies provide valuable insights to guide future research and development. Additionally, we also review the common additive phases in cold-sprayed Zn coatings and their impacts on mechanical and tribological properties and corrosion resistance. Adding materials such as graphene, carbon nanotubes, and various nanoparticles have been introduced to achieve synergistic effects. For example, graphene forms a barrier layer within Zn coating that remarkably enhances its resistance to corrosion. Research indicates that when an appropriate amount of graphene is added to Zn coating, the corrosion current density is greatly reduced compared with Zn coating, which indicates a significant improvement in corrosion resistance. These additions can also improve tribological properties and reduce friction and wear. Furthermore, we also summarized post-treatment technologies such as heat treatment and shot peening. The influence of these post-treatment methods on cold-sprayed Zn-based coatings are evaluated based on experimental results and theoretical analysis. In general, heat treatment can relieve internal stress, improve crystallinity, and enhance the bonding strength between the Zn-based coating and the substrate. In an experiment with heat treatment, the adhesive strength was increased significantly when the samples were heated to an appropriate temperature and maintained for a certain period. Similarly, shot peening can refine surface grains, increase the surface hardness, and enhance fatigue resistance. Finally, we also outline prospects for future developments in cold-sprayed Zn-based coatings. It is expected that more advanced spraying techniques and new adding materials will emerge to further optimize the performance of cold-sprayed Zn-based coatings.
  • Effect of Sandblasting Pre-treatment on the Growth Characteristics of the Tantalum Anti-hydrogen Embrittlement Layer within the Target for Accelerator-driven Neutron Source
    ZHANG Fanxi, XIE Yupeng, WANG Yaru, HU Yaocheng, CHEN Chen, WANG Sheng
    China Surface Engineering. 2026, 39(3): 71-82. https://doi.org/10.11933/CSE2026176
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    Accelerator-based boron neutron capture therapy (AB-BNCT) has attracted significant attention as an emerging cancer-treatment technology. The establishment of a stable neutron production target system is crucial, and the design and fabrication of a reliable anti-hydrogen embrittlement layer is crucial in ensuring long-term stability. This study investigates the effects of substrate pretreatment on the structure and performance of an anti-hydrogen embrittlement layer for accelerator-based neutron production. The substrates were treated using glass beads of varying mesh sizes, followed by the deposition of tantalum (Ta) coatings of different thicknesses via magnetron sputtering. This approach facilitated the analysis of the growth mechanism of the Ta coatings on pretreated substrates. Laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) were used to examine the substrate microstructure before and after sandblasting. The surface roughness was evaluated using LSCM before and after film deposition. The results revealed that as the glass bead mesh size increased from 36 to 360, the surface roughness of the substrate decreased from 5.76 nm to 1.53 nm, representing a reduction of 4.23 nm. A moderate increase in the roughness of the surface enhanced the adhesion of the anti-hydrogen embrittlement layer to the substrate, thereby improving its protective performance. SEM and LSCM observations indicated that the deposited coating inherited the initial morphology of the substrate, forming a continuous layer at a thickness of 5 μm. The crystal structure of the anti-hydrogen embrittlement layer was analyzed by X-ray diffraction (XRD), and the chemical properties of the films were further investigated by X-ray photoelectron spectroscopy (XPS). Finally, stress measurements were conducted to evaluate the overall quality of the films. However, at a thickness of 20 μm, samples with higher surface roughness exhibited growth-induced voids. X-ray diffraction (XRD) analysis revealed that, as the coating thickness increased, the crystallographic structure of the Ta coating evolved on the copper (Cu) substrate. During the nucleation stage (1 μm), α-Ta was preferentially formed, whereas during the growth stage, α-Ta gradually transformed into β-Ta. When the coating thickness reached 20 μm, samples with lower roughness were predominantly composed of the β phase. Increased roughness contributed to grain refinement; however, for coatings beyond a certain thickness, finer grains were observed in samples S4 (5 μm) and S5 (20 μm). No cracks or delamination were observed in the 20 μm-thick Ta coatings deposited on all pre-treated substrates. Film quality was further assessed through stress measurements, revealing an inverse relationship between coating thickness and internal stress. Measurements demonstrated a significant stress reduction with increasing film thickness. This reduction was attributed to the stronger influence of the substrate on 1 μm-thick coatings. Notably, after sandblasting the substrate with 360-mesh glass beads, the stress of the 20 μm-thick Ta coating was reduced to only 0.35 GPa. Additionally, the pits generated by sandblasting induced compressive stress during the intermediate growth stage, promoting adhesion between the Ta antihydrogen embrittlement layer and substrate. Comparative analysis of different samples demonstrated that, under identical magnetron sputtering parameters, substrates treated with 220-mesh glass beads exhibited a smooth and dense surface morphology, with the corresponding 20 μm-thick Ta coating exhibiting a stress level of only 0.35 GPa. The fabrication of an anti-hydrogen embrittlement layer was successfully achieved by sandblasting pre-treatment combined with magnetron sputtering. An optimal sandblasting mesh size was selected to ensure reliable adhesion of the subsequent lithium reaction layer. This study provides valuable insights into the development of stable and efficient accelerator-based neutron production targets for AB-BNCT while addressing critical engineering challenges when implementing anti-hydrogen embrittlement layers in accelerator-driven neutron production targets.
  • Research on the Effect of Ultrasonic Impact Treatment on the Surface Integrity and Corrosion Resistance of Laser Cladding Fe-based Coatings
    WANG Xinsheng, ZHENG Yang, LIU Jian, CAI Zhihai, DU Xian, WANG Haidou
    China Surface Engineering. 2026, 39(3): 83-94. https://doi.org/10.11933/CSE2026071
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    45CrNiMoVA high-strength steel is widely used in manufacturing the torsion shafts of armored vehicles owing to its high strength, high toughness, high plasticity, and excellent fatigue resistance. However, it was suffered from stress corrosion cracking in corrosive environments; to address this issue, protective coatings are typically applied to the substrate surface to extend the service life of the components. In this study, an iron-based coating was prepared on the surface of 45CrNiMoVA high-strength steel using (by) laser cladding technology, and the coating surface was strengthened using ultrasonic impact treatment (UIT). Currently, research on the changes in microstructure and mechanical properties of high-hardness coatings after ultrasonic impact is limited, with most studies focusing on coatings with hardness below 600 HV0.1. The objective of this study was to investigate the strengthening effect of UIT on high-hardness coatings and explore the combined effect of laser cladding and UIT on the strengthening of high-strength steel components. A laser confocal microscope was used to determine the surface roughness values of the coatings before and after UIT. The phase compositions and cross-sectional microstructures of the coatings before and after UIT were observed by X-ray diffraction analysis and optical microscopy. The residual stress values of the coating before and after UIT were measured using an X-ray stress analyzer. The microhardness of both types of coatings was tested using a Vickers microhardness tester. Electrochemical corrosion tests were conducted on the substrate and the coating (both before and after UIT) in 3.5wt.% NaCl solution using a three-electrode system electrochemical workstation. The results is showed that the surface roughness of the iron-based coating reached 12.76 μm. After UIT, the peak-shifting and valley-filling effects induced by surface plastic flow made the surface smoother and reduced the surface roughness to 2.05 μm (83.93% reduction). The iron-based coating primarily consisted of equiaxed grains, dendrites, and columnar grains. After UIT, an impact layer of thickness ~15 μm was formed on the surface, with grain fragmentation, compression, and elongation observed in the surface layer, along with plastic flow along the processing direction. The grain density increased; however, no significant grain changes were observed in the subsurface or interior of the coating. After UIT, the coating surface transformed from the Fe-Cr phase to a mixture of Fe-Cr and Cr0.19Fe0.7Ni0.11 phases. The (110) diffraction peak shifted to the right and its width increased, indicating grain refinement and the presence of residual compressive stress. The stress state of the coating after UIT changed from residual tensile stress (97 MPa) to residual compressive stress (-200 MPa). The maximum residual compressive stress was observed at the surface, and the residual compressive stress gradually decreased along the depth of the coating. Hardness testing was revealed that the maximum hardness at the top increased from 772 HV0.1 to 889 HV0.1. Because of the greater hardness of the coating, its resistance to plastic deformation was strong. After UIT, the coating hardness significantly increased within a 100-μm distance from the surface, with the improvement effect gradually weakening along the depth. The substrate exhibited poor corrosion resistance, the coating potential shifted positively by 130 mV after UIT, and the self-corrosion current density decreased by 56.48%. The reduced surface roughness, grain refinement, work hardening, and the presence of residual compressive stress on the UIT-treated coating hindered the infiltration of corrosive ions, making the coating more resistant to corrosion in the 3.5wt.% NaCl solution. Therefore, the process adopted in this study helped overcome the difficulties associated with surface strengthening of traditional hard coatings and provided a reference for future research and application of laser cladding and UIT for high-hardness coatings.
  • Influence of Surface Grooves and Fillers on the Tribological Behavior of Copper-based Powder Metallurgy Materials under Flat-to-flat Contact Configuration
    WANG Anyu, WANG Quan, MO Jiliang, XIONG Qing, QIU Xiaoli
    China Surface Engineering. 2026, 39(3): 95-106. https://doi.org/10.11933/CSE2026166
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    Copper-based powder metallurgy materials have emerged as attractive candidates for the brakes and clutches of high-speed trains, wind power yaw systems, mining trucks, and automobiles, owing to their good thermal conductivity, excellent wear resistance, and stable friction coefficient. However, the reliability and safety of equipment services have been drastically reduced by the increasingly harsh working environment, which is heavily influenced by the wear of copper-based powder metallurgy materials, functional degradation of parts, potential internal fatigue, and other problems caused by friction and vibration. Finally, friction-induced vibration and noise (FIVN) is triggered, a phenomenon that has puzzled researchers for several years. After years of sedimentation, although extensive research methods and theories related to FIVN have been developed, relevant research still needs to be pursued due to the arcane mechanism of its generation and the limited effectiveness of suppression methods. To address the severe challenges caused by friction and wear, innovations in surface texture technology, which play an increasingly important role in antifriction and antiwear applications, should be urgently developed to ensure the safe and reliable service of components. Considering that interface wear and debris rheology are the main culprits of the FIVN, a previous study found that a surface filled with gray iron HT300 could reduce interface wear, maintain the steady-state of the friction syetem, and effectively inhibit the generation of the FIVN. Therefore, to further explore the application scope of the surface filled with gray iron HT300 to reduce FIVN and fully reveal the mechanism of its interface tribological behavior is critical. In this study, the tribological performance of copper-based powder metallurgy materials is improved, and the design method for a surface filled with gray iron HT300 is further extended to a flat-to-flat contact configuration. First, grooves are machined on the surfaces of friction blocks made from copper-based powder metallurgy, and the grooved blocks are then filled with gray cast iron (HT300) to obtain three types of samples with different surface characteristics: original friction blocks, grooved friction blocks, and friction blocks filled with gray cast iron. Tribological tests are then performed on friction block samples with different surface characteristics and friction disc samples in a flat-to-flat contact configuration. By combining finite element simulations and numerical analyses, the synergistic effects of surface grooves and gray cast iron on the frictional behavior of copper-based powder metallurgy materials are thoroughly explored. Based on signal processing, micromorphology analysis, and theoretical analysis, the results show that copper-based powder metallurgy friction blocks with different surface characteristics exhibit varying wear properties and interface contact states, ultimately leading to different system responses. Compared with the original and grooved friction blocks, the friction blocks filled with gray cast iron significantly increased the contact area at the disc-block interface. They expanded the contact area, thereby alleviating stress concentration and effectively improving interface wear. Compared with the original and grooved friction blocks, the friction blocks filled with gray cast iron significantly enhance the disc-block interface contact degree and expand the contact area, thereby alleviating stress concentration and effectively improving the wear state at the interface. Additionally, the friction blocks filled with gray cast iron reduced the contact inclination angle at the disc-block interface, thus enhancing the system stability and effectively attenuating FIVN intensity. Therefore, an innovative surface design combining surface grooves with gray cast iron fillers meets the requirements for improving the tribological performance of copper-based powder metallurgy materials.
  • Study on Additive Re-manufacturing of CuCrZr Crystallizer by Laser-assisted Cold Spray
    FU Wei, WANG Chenqing, LI Bo
    China Surface Engineering. 2026, 39(3): 107-119. https://doi.org/10.11933/CSE2026322
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    CuCrZr alloy, owing to its excellent comprehensive performance, has become an ideal material for manufacturing continuous casting mold copper plates. However, under harsh service conditions, mold copper plates encounter failures such as thermal fatigue cracks, creep deformation, surface wear/corrosion and cooling water erosion, etc. Existing surface repair and strengthening technologies still have certain limitations. Therefore, it is necessary to develop a new additive re-manufacturing technology for failed CuCrZr mold copper plates. Laser-assisted cold spray (LACS) is an emerging laser hybrid manufacturing technology that offers high deposition efficiency, minimal thermal damage to the substrate, and good interface bonding. It shows great potential for surface strengthening and additive manufacturing/re-manufacturing of metal components. In this study, LACS is employed to achieve additive re-manufacturing for failed CuCrZr substrates. The influence of different laser powers on the microstructure of the deposited layer is systematically discussed. Subsequent heat treatment of the re-manufactured layer is carried out considering actual service conditions, and the thermal conductivity and interface bonding strength of the re-manufactured layer are analyzed in depth. The results show that the introduction of laser irradiation significantly improves the bonding between the additive re-manufactured layer and the CuCrZr alloy substrate. Without laser irradiation assistance, obvious gaps exist at the interface between the deposited layer and the substrate. As the laser power increases, the gaps due to poor bonding at the interface are markedly reduced. At 1 500 W laser irradiation, the bonding interface between the deposited layer and the substrate is very tight. However, at 2 000 W laser irradiation, some pores appear at the bonding interface. The introduction of laser irradiation also helps to improve inter-particle bonding with the deposited layer. The porosity of the deposited layer without laser irradiation and with 1 000, 1 500 and 2 000 W laser irradiation are 6.27%, 3.52%, 0.43% and 0.56%, respectively. Wihout laser irradiation, the additive re-manufactured CuCrZr alloy layer contains a large number of larger-sized pores. As the laser power increases, the number of pores decreases and the deposited layer becomes denser. The average microhardness values of the deposited layer under 1 000, 1 500 and 2 000 W laser irradiation are 153.482, 167.714, 170.067 and 168.789 HV0.2, respectively. Laser irradiation intensifies the plastic deformation of the deposited particles, inducing a work-hardening effect and thus higher hardness. XRD results show that the samples with laser irradiation and subsequent heat treatment maintain the same copper solid-solution phase as the sample without laser assistance, with no other imputity phase such as copper oxides detected. Post heat-treatment results reveal that the thermal conductivity of the 2 mm re-manufactured layer, the 1 mm re-manufacturing layer+1 mm substrate, the 2 mm substrate are 305.44, 315.92 and 334.2 W/(m·K), respectively. The thermal conductivity of the LACS-CuCrZr re-manufactured layer is close to that of the cast CuCrZr substrate, which is attributed to the dense microstructure of the LACS-CuCrZr re-manufactured layer. The interface bonding strength between the LACS-CuCrZr re-manufactured layer and the CuCrZr crystallizer substrate before and after heat treatment is 96.39 and 121.43 MPa, respectively. Due to the synchronous coupling laser heating, the plastic deformation at the material at the interface between the re-manufactured layer and the substrate is enhanced, resulting in a higher bonding strength. Moreover, the subsequent heat treatment further improves the interface bonding. The fracture morphology is characterized by pits formed by subsequent particle impact within the re-manufactured layer. The failure location lies within the coating, and the failure mode is typical cohesive failure. The bonding strength at the interface between the re-manufactured layer and the substrate is greater than that within the re-manufactured layer. The research results demonstrate that the additive re-manufactured CuCrZr alloy layer prepared at a laser power of 1 500 W exhibits excellent overall forming quality and outstanding comprehensive performance: porosity of 0.43%, microhardness of 170.067 HV0.2, thermal conductivity of 334.2 W/(m·K), and interface bonding strength of 121.43 MPa. This work preliminarily verifies that LACS technology can serve as a new method for surface strengthening and additive re-manufacturing of crystallizer copper plates, providing a theoretical basis and technical support for its engineering application.
  • Effect of Annealing Time on the Properties of Magnetron Sputtered Au-Ni, Cr Composite Coatings
    GUO Junde, LI Jiale, QIAO Li, ZHANG Xinyun, WANG Dong, WANG Peng
    China Surface Engineering. 2026, 39(3): 120-129. https://doi.org/10.11933/CSE2026069
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    The solar sail drive plays a pivotal role in the sustainable energy supply of satellites. In the long-term transmission process of current and signals, approximately 20% of solar sail drive device failures are attributed to friction wear and lubrication failure, resulting from conductive slip ring short circuits and stuck conditions. It is noteworthy that the majority of conductive slip ring materials currently employed are gold alloys. However, the use of gold alloys in these devices can lead to an increase in resistivity, thereby reducing the overall effectiveness of the system. To enhance the friction performance of the gold-based coating, it is imperative to minimize the increase in resistivity of the coating. To this end, the present study employed DC magnetron sputtering to prepare gold-based coatings on CuCrZr alloys and Si wafers, with target sputtering powers of 0, 30, 50, and 100 W, respectively. The transition layer comprised a 150 nm-thick Ni layer, which was subjected to annealing treatments at 250 ℃ for 5 and 20 h. The coatings were also subjected to a series of characterization and experimentation to investigate the effects of co-doping Ni and Cr and performing vacuum annealing treatment on the structure and comprehensive properties of the coatings. The properties investigated included resistivity, residual stress, nano-hardness, and friction and wear properties. The results demonstrate that the atomic percentages of Ni and Cr elements in the coatings increase with the increase of sputtering power of Ni and Cr targets, and the vacuum annealing treatment does not produce large changes in the atomic percentages of Ni and Cr elements.The Au, Ni, and Cr elements in the coatings show a homogeneous distribution, and the vacuum annealing treatment does not have an effect on the homogeneous distribution of the Au, Ni, and Cr elements. The coatings exhibit optimal orientation, characterized by the presence of (111) and (220) diffraction peaks. The incorporation of Ni and Cr into the coating material results in a diminution of the intensity of the (111) diffraction peak. The effect of annealing treatment on (111) diffraction peak intensity is complex. The modification of the coating grain size by Ni, Cr doping and annealing treatment is multidimensional. Increasing the Ni, Cr target power and annealing both lead to an increase in resistivity, a decrease in residual stress, and even a change in type and increase in nanohardness of the coating. The lowest coefficient of friction for pure gold coatings is due to the high plasticity of gold, while the highest wear rate is due to the low hardness of gold. Doping with Ni, Cr leads to an increase in the coefficient of friction and a decrease in the wear rate of the coating. The fluctuation of the friction coefficient of the coating flattens out as the Ni, Cr target power increases. Vacuum annealing treatment gradually improves the fluctuation of the friction coefficient of the coating. After the vacuum annealing treatment, the friction coefficient increases with the extension of the annealing time, and the wear rate increases and then decreases with the extension of the annealing time, which is related to the change of the overall properties of the coatings after the annealing process.There is an adhesion phenomenon on the friction surface of the coatings with the Ni, Cr target power of 0 W, which indicates that the wear of the coatings is mainly based on adhesive wear and plastic deformation. With the increase of Ni, Cr target power, fuzzy furrows appeared on the friction surface of the coating, indicating that the wear of the coating was dominated by abrasive wear and fatigue wear. The co-doping of Ni, Cr and the solid solution strengthening and fine crystallization due to the annealing treatment would increase the nanohardness of the coatings and thus improve the wear resistance. However, there is no significant inhibitory effect on the resistivity increase.
  • Effect of Paraffin on the Film-forming Behaviour of Phosphate Saponification of Galvanized Steel Sheets
    XIONG Meng, HE Xiao, ZHOU Chuanbo, YAO Peichen, LIU Huicong, ZHU Liqun
    China Surface Engineering. 2026, 39(3): 130-137. https://doi.org/10.11933/CSE2026070
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    Galvanized steel sheets have become indispensable materials in various industries including construction, automotive manufacturing, and home appliances owing to their excellent corrosion resistance, cost-effectiveness, and mechanical properties. The rapid development of industrial technology has further broadened their applications, particularly in critical infrastructures, such as nuclear power plants. In these settings, prestressing pipes, which are often composed of galvanized steel, are distributed within the containment shells. The surface smoothness of these pipes is critical because it directly affects the friction coefficient between the strands within the pipes and the pipe surfaces. This ultimately influences the effectiveness of prestressing on the containment shells. Enhancing the surface properties of galvanized steel sheets is crucial for high-stakes applications. Phosphate saponification is a crucial method for improving the surface properties of galvanized steel sheets. This process enhances corrosion resistance and provides the desired surface smoothness for specific industrial applications. Among various additives, paraffin wax has emerged as a promising lubricant, drawing significant interest for its integration into the phosphate saponification process. This study aimed to investigate the role of paraffin wax emulsion in the phosphating saponification treatment of galvanized steel sheets, focusing on its influence on the film-forming behavior and associated surface performance characteristics. The research adopts galvanized steel sheets were used as the primary research object, and a trans-phase emulsification method was employed to prepare a paraffin wax emulsion. This method ensured the production of a stable emulsion with uniformly distributed paraffin wax particles. The prepared emulsion was subjected to phosphate saponification. This study systematically examined the effect of paraffin wax emulsions on the film-forming behavior, surface friction coefficient, water resistance, and corrosion resistance of galvanized steel sheets. Several comparative experiments were conducted to assess the effects of the paraffin wax emulsion. These experiments evaluated the key performance indicators before and after the addition of the paraffin wax emulsion to the phosphate saponification process. The friction coefficient of the treated surface was measured using a friction tester, and the water resistance was evaluated using immersion tests. The corrosion resistance was assessed using electrochemical impedance spectroscopy and salt spray tests. The surface morphology and structural characteristics of the films were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). This study has several significant findings. The addition of paraffin wax emulsion to the phosphate saponification treatment notably reduced the friction coefficient of the galvanized steel surface. This improvement in surface smoothness enhances the efficiency of prestressing applications in nuclear containment shells and other industrial applications. Moreover, the treated surfaces exhibited superior water resistance, as evidenced by the prolonged immersion test durability, without significant degradation. The corrosion resistance of the galvanized steel sheets also significantly improved, with the paraffin wax emulsion enhancing the integrity and uniformity of the phosphate saponification films. SEM and EDS analyses confirmed the formation of a dense and well-distributed film with paraffin wax particles effectively integrated into the film matrix. This study further elucidates the mechanism by which paraffin wax emulsions enhance the phosphate saponification process. The emulsion acts as a lubricant and film modifier, promoting uniform deposition during the phosphating stage and providing additional hydrophobicity and barrier protection during the saponification stage. These combined effects contributed to the observed improvements in surface performance characteristics. In conclusion, integrating a paraffin wax emulsion into the phosphate saponification treatment process offers a novel and effective approach to enhancing the surface properties of galvanized steel sheets. By reducing surface friction, improving water resistance, and bolstering corrosion resistance, this method addresses the critical performance requirements for applications in construction, automotive manufacturing, and nuclear infrastructure. This phosphating and saponification process can effectively reduce the surface friction coefficient by 50%, and improve the water resistance and corrosion resistance of the galvanized steel plate surface. Future research could explore the long-term durability of the treated surfaces under varying environmental conditions and extend the application of this technique to other metal substrates.
  • Effect of Combined EDM and Abrasive Flow Machining on Pore Surface of DD5 Single Crystal Alloy
    WU Yuchun, LI Ke, NIU Fan, CHEN Taili, SUN Jiang, JIAO Wenjian, SUN Qinghua, CAI Zhenbing
    China Surface Engineering. 2026, 39(3): 138-151. https://doi.org/10.11933/CSE2026068
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    The inner wall quality and machining precision of a blade film hole significantly influence the cooling effect, which is related to the stability of the entire engine. To achieve the efficient preparation of air film holes on aviation turbine blades, the optimum electrical discharge machining (EDM) hole-making technology was investigated to improve the inner wall quality of the air film holes. For the DD5 Ni-base single-crystal superalloy with a thickness of 2 mm, EDM was performed by varying the machining current and pulse width. The composite abrasive flow machining (AFM) of a small hole for the completion of the EDM hole-making process can effectively improve the defect surface of the inner wall of the small hole. It is found that with an increase in the machining current and pulse width, the aperture size of the inlet and outlet increases, the hole taper and roundness first decreases and then increases, and an overall trend of decline is exhibited with increasing pulse width. When the current is 3 A, the overall taper of the holes is small. Serious re-melting layers and microcracks are produced on the inner wall of the EDM hole. After the compound AFM process, the re-melting layer on the inner wall is removed using abrasive particles. In addition, the inner wall roughness of the EDM hole is higher, the inner wall is enriched with O, except for the main elements of the alloy, and the O content in the inner wall of the composite AFM hole is lower. When the processing voltage and feed speed are constant, processing current is 3 A, and pulse width is 3 μs, the drilling effect of DD5 single-crystal alloy plate with thickness of 2 mm is found to be the best. The higher the temperature before the turbine, the stronger the thrust provided by the aeroengine. However, excessive temperatures pose a severe challenge to the temperature-bearing capacity of engine components. The blade can be effectively protected by preparing gas film holes on the blade. Moreover, the inner wall quality and machining accuracy of the blade gas film holes have a significant influence on the cooling effect of the entire blade, which is related to the running stability of the entire aeroengine. Compared with other microhole machining technologies, EDM can achieve high-efficiency, clean, and batch machining, and has high applicability to machining materials, that suits all types of high-strength and difficult-to-machine metals. To realize efficient preparation of gas film holes on aviation turbine blades, the best EDM hole-making process is explored to improve the inner wall quality of the gas film holes. For nickel-based single-crystal superalloy DD5 with a thickness of 2 mm, EDM was performed by changing the machining current and pulse width, and orthogonal experiments with different machining parameters were designed. The composite abrasive flow machining (AFM) of small holes with the EDM hole-making process was completed, which effectively improved the defect surface of the inner walls of the small holes. With an increase in the machining current and pulse width, the sizes of the inlet and outlet apertures increase, the hole taper and roundness first decrease and then increase, and the overall trend shows a decrease with an increase in pulse width. When the machining current increases, the energy of the EDM increases indirectly, and when the pulse width increases, the discharge time of a single pulse increases, which also increases the discharge energy. The energy obtained from the plasma channel on the surface of the workpiece also increases, and the material removal efficiency increases per unit time, eventually leading to an increase in aperture. At a current of 3 A, the overall taper of the small holes is small. Serious defects such as a remelting layer and microcracks are produced on the inner wall of the small holes machined by EDM. After the composite AFM process, the remelting layer on the inner wall is removed under the action of abrasive particles, which mainly achieves the effect of uniform microcutting through the collision between the abrasive and inner wall. Simultaneously, owing to the existence of a remelting layer, the surface of a small hole machined by EDM is composed of many craters with different depths, which increases the overall roughness. In addition to the main elements in the alloy, the inner wall is enriched with O. In a high-temperature environment, Ni and Al with high oxygen affinity in the alloy preferentially react with O2 to generate oxides, and Co and Cr also generate their corresponding oxides. The O content in the inner wall of the small hole caused by the composite AFM process is low, which effectively removes the surface-remelting layer. Through range analysis, the pinhole performance is evaluated after a two-factor four-level orthogonal test, and the factors are sorted according to the range value. The most significant factor affecting the machining quality of the pinhole is found to be the machining current, followed by the pulse width. When the parameters such as machining voltage and feed rate are fixed, machining current is 3 A, and pulse width is 3 μs, the best hole-making effect is obtained for DD5 single crystal alloy plate with a thickness of 2 mm. Composite machining using EDM and abrasive flow thus provides a reference for the preparation of blade gas-film holes.
  • Promoting Effect of Hydrogen in Hot Wire Enhanced Plasma Nitriding of Pure Iron
    TANG Zhengtao, ZHOU Yanwen, FU Xingqi, YU Pengchao, ZHAO Zhuo, ZHOU Jinlong, LÜ Zhe
    China Surface Engineering. 2026, 39(3): 152-161. https://doi.org/10.11933/CSE2026177
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    ：To address the insufficient wear resistance and limited service life of magnetic particle clutches and braking devices utilizing pure iron substrates—characterized by excellent magnetic properties but low hardness and poor durability—this study proposes a surface engineering strategy involving plasma ion nitriding with hot filament enhancement. This approach aims to fabricate a wear-resistant nitrided layer with preserved magnetic permeability, thereby extending operational longevity while maintaining cost-effectiveness. Compared to conventional gas nitriding, plasma ion nitriding offers superior advantages, including enhanced energy efficiency, precise control over the nitrided layer structure, and broader applicability to challenging materials. The introduction of tungsten filaments within the vacuum chamber significantly enhanced gas ionization, thereby accelerating the nitriding kinetics and improving the process efficiency. Under optimized conditions (520 ℃, 0.4 Pa), systematic variations in the atmosphere and thermal processes were employed to investigate the catalytic role of hydrogen and the effects of staged thermal alloying (insulation). The phase composition, cross-sectional morphology, layer depth, and tribological properties of the nitrided layers were characterized by X-ray diffraction (X’Pert Powder), scanning electron microscopy (ΣIGMA HD), micro-Vickers hardness testing (Q10M), tribometry (MS-T3001), and step profiler (Alpha-step D-100). Results indicate that a pure nitrogen atmosphere produced a 500 μm-thick nitrided layer comprising ε-Fe3N (29%) and γ'-Fe4N (71%) phases, with a curved compound-diffusion layer interface due to low nitrogen diffusivity (13.88 μm2/s) and preferential short-circuit diffusion along grain boundaries. Within the diffusion layer, nitrogen atoms dissolved into the octahedral interstices of the ferrite lattice. The nitrogen atoms exceeded the solubility limit of the ferrite precipitates as nitrides. Two distinct precipitation morphologies were observed: relatively long needle-like nitrides preferentially precipitated at the grain boundaries, whereas comparatively shorter rod-like nitrides were dispersed intragranularly. This intragranular precipitation pattern adhered to the Baker-Nutting orientation. In contrast, the introduction of hydrogen and the two-stage thermal alloying markedly altered the phase distribution and diffusion dynamics. The modified process yielded a 1 000 μm-thick nitrided layer with a refined phase ratio (6% ε-Fe3N vs. 94% γ'-Fe4N) and enhanced nitrogen diffusivity (55.55 μm2/s). Hydrogen mediation promotes homogeneous lattice diffusion, resulting in a planarized compound-diffusion interface. Notably, a 600 μm-wide hardness plateau (100-700 μm depth) emerged due to nitrogen redistribution during alloying stages. This plateau arose from the decomposition of nitrogen-rich phases under an interrupted nitrogen supply, followed by inward nitrogen migration driven by concentration gradients and solid-solution strengthening. The plateau with a relatively slow change in the hardness value provides good support for the hard and brittle compound layer-soft matrix. Meanwhile, under the optimized processes, the diffusion rate of nitrogen increased significantly, and the hardness of the nitriding diffusion layer was enhanced by solid-solution strengthening. The synergistic effects of these two factors weakened the “eggshell effect.” The synergistic effects of hydrogen and staged alloying significantly improved the mechanical and tribological performance. Wear rate decreased by 15-fold (from 2×10-4 to 1.3×10-5 mm3·N-1·m-1), while the friction coefficient dropped by 42.9% (0.42→0.24). The width and depth of the friction and wear marks decreased significantly, and the microstructural analysis revealed a transition in wear mechanisms from severe adhesive/oxidative wear to mild abrasive wear, which was attributed to the support of the hardened subsurface platform for the brittle compound layer. Crucially, the magnetic properties of the pure iron substrate remain uncompromised; for example, it exhibits good saturation magnetization and extremely low coercivity. This work demonstrates that hydrogen-enhanced plasma nitriding coupled with staged thermal alloying enables the fabrication of ultrathick, mechanically graded nitrided layers with balanced strength-toughness properties. These findings provide novel insights for industrial applications of plasma nitriding, offering a viable pathway to enhance the surface durability of magnetic components without sacrificing their intrinsic functional performance. The proposed methodology has a significant potential for advancing precision manufacturing and automated systems that require highly reliable and extended service intervals.
  • Preparation and Properties of Sepiolite-modified Epoxy Resin Composite Coatings
    WANG Jie, CUI Xuejun, CHEN Xingyou, QI Yuming, HUANG Linjie, CHENG Fei
    China Surface Engineering. 2026, 39(3): 162-175. https://doi.org/10.11933/CSE2026073
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    Severe corrosion poses a significant threat to industrial infrastructures, leading to substantial economic losses and material degradation. Organic coatings have emerged as cost-effective and practical solutions to address this challenge. Among these, epoxy resin (EP) coatings are widely employed owing to their exceptional adhesion strength, chemical inertness, and robust barrier properties, which effectively isolate metal substrates from corrosive media such as moisture, oxygen, and chloride ions. However, the inherent limitations of conventional EP coatings, including high brittleness, low shrinkage resistance, and susceptibility to microcrack propagation under prolonged environmental stress, compromise their long-term protective performance. Recent advancements have focused on the development of polymer/silicate clay nanocomposites to overcome these drawbacks. The incorporation of organically-modified silicate into EP (OMSEP) matrices has shown promise for enhancing the coating functionality through nanoscale reinforcement. The layered structure of silicate clay acts as a tortuous barrier, significantly impeding the diffusion pathways of corrosive species while improving mechanical integrity. Moreover, organic modification of clay facilitates uniform dispersion within the polymer matrix, enabling synergistic interfacial interactions that elevate the thermal stability and crosslinking density. This study specifically investigates the corrosion protection mechanism of OMSEP/EP nanocomposite coatings on microarc-oxidized magnesium substrates. By leveraging in-situ intercalation polymerization techniques, the nanocomposite achieved optimized exfoliation of the clay layer, resulting in a denser and more impermeable coating structure. Electrochemical impedance spectroscopy (EIS) and salt-spray tests demonstrate a 2 orders of magnitude in the impedance modulus compared to pure EP coatings. The improved performance is attributed to the dual barrier effect: physical obstruction by silicate layers and enhanced crosslinking, which minimizes defect formation. These findings offer critical insights for designing next-generation protective coatings for lightweight magnesium alloys used in aerospace and automotive applications, where a combination of corrosion resistance and mechanical durability is paramount. Mg alloys suffer from poor corrosion resistance and weak wear and impact resistance, making them highly susceptible to “corrosion failure” and “wear failure” in service environments. Addressing these issues has become a critical technical challenge for the engineering applications of lightweight advanced equipment. In this study, sepiolite (SEP)-modified epoxy resin (EP) was employed to enhance the protective capability of EP coatings on microarc-oxidized magnesium alloys. Initially, KH570 was utilized to modify SEP, producing organically-modified sepiolite (OMSEP). Subsequently, a polysilazane (PSZ) coating was deposited on the micro-arc oxidation (MAO) magnesium alloy substrate via dip coating. Finally, OMSEP/EP composite coatings were prepared by scraping with a coater. The structure and thermal properties of OMSEP were characterized using Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The surface morphologies of SEP before and after modification, along with the composite coatings, were examined using scanning electron microscopy (SEM). The hydrophobicity was assessed using contact angle measurements. The corrosion resistance was evaluated using electrochemical impedance spectroscopy (EIS) and salt-spray testing. The mechanical properties of the composite coatings, including wear resistance and adhesion strength, were determined using a triboelectrochemical test system and a digital display adhesion tester, respectively. These results demonstrate that OMSEP was successfully synthesized. The modification of epoxy resin (EP) with 3wt.% OMSEP resulted in a composite coating with increased thickness of 9.18 μm compared to the pure EP coating of 4.49 μm. The water contact angle increased from 76.8° to 101.7°, indicating a transition from hydrophilic to hydrophobic. The impedance modulus (|Z|) improved by two orders of magnitude, reaching 1010 Ω. The pitting initiation time increased from 51 s to 85 s. After a 45-day salt-spray test, no significant accumulation of corrosion products or lateral spreading was observed around the scribe on the composite coatings, indicating a 50% improvement in the corrosion protection performance. Concurrently, the friction factor decreased from 1.08 to 0.41, demonstrating enhanced wear resistance, while the adhesion strength increased from 0.82 MPa to 1.57 MPa. A multi-layer protective system was constructed through a “sandwich”-structured coating design, effectively blocking the infiltration of corrosive media.
  • Effect of Current Density on the Current-carrying Tribological Properties of Ag-Ni Composite Coating
    HUANG Qirui, LI Na, SONG Chenfei, LU Huanhuan, LIU Zili, HOU Xinbin, ZHANG Yongzhen
    China Surface Engineering. 2026, 39(3): 176-186. https://doi.org/10.11933/CSE2016178
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    Electrical connectors are widely used in the aerospace industry, rail transit, and new energy vehicles. As typical current-carrying frictional pairs, electrical connectors are key components that determine equipment power and signal transmission. With the continuous advancement of electrification, the reliability and performance requirements for electrical connectors have become more stringent. Unlike traditional mechanical wear, the friction and wear of electrical contacts under current-carrying conditions are influenced by force-thermal-electrical coupling effects, leading to more complex failure modes and damage types. Consequently, the failure mechanisms of electrical connector contacts have attracted significant attention in both academic and industrial fields. Ag is one of the most commonly used coating materials for electrical contact surfaces. To investigate the damage mechanisms of Ag-coated electrical contacts, a sliding current-carrying wear test was conducted using ball-disk frictional pairs. Single-point contact was used to simulate the friction and wear of a single-contact finger during the insertion process. During the experiment, the changes in current-carrying properties and the evolution of material damage mechanisms were examined under different current densities. The results showed that the average friction coefficient in the steady state increased with an increase in current density in the contact area. At high current densities (21.4 and 35.7 A/mm2), the friction coefficient suddenly changed after a period of smooth operation. Furthermore, as the current density increased, the timing of this abrupt change occurred earlier: at 21.4 A/mm2, the average friction coefficient during stabilization was approximately 1.01, followed by a sudden drop to about 0.69 at 1 050 s. At 35.7 A/mm2, the friction coefficient experienced an abrupt change at 700 s, decreasing from 1.1 to 0.72 within 10 s. The oxygen contents in the wear zones of the ball and disk under different operating conditions were compared. Due to passivation from Ni oxidation, surfaces with high Ni content exhibited no significant oxidation (disk samples at current densities below 7.2 A/mm2). The degree of oxidation in the wear zone increased after the appearance of Cu on the surface. At 35.7 A/mm2, the oxidation level of the disk sample was higher than that of the ball sample. Because the ball was ground repeatedly along the same circular path on the disk surface, its exposure to the external atmosphere was limited during grinding friction, resulting in relatively lower oxidation. The current-carrying wear mechanism of the composite coating involved adhesive wear accompanied by abrasive and oxidative wear. Arc ablation was not observed in this study. The temperature increase at the contact interface of the friction pair resulted from the combined effects of frictional heat and Joule heat, with frictional heating predominating at low current densities. When the current density exceeded 7.2 A/mm2, Joule heat played a dominant role in the temperature rise, which increased rapidly with increasing current density. Temperature increase is the primary mechanism by which current promotes adhesive wear; it softens the contact material and alters the properties of the contact interface. This research not only provides a simple and effective approach for analyzing the current-carrying performance and wear mechanisms of silver-plated electrical contacts under varying current densities but also offers a theoretical foundation for the reliable design and damage protection of silver-plated electrical connector contacts.
  • Rolling Wear and Contact Fatigue Damage Behavior of 42CrMo Bearing Steel with Laser Solid-state Phase Transformation
    YU Faxing, YAO Xinyu, DING Haohao, WANG Liang, ZHANG Qunli, SHEN Zhixin, WANG Wenjian
    China Surface Engineering. 2026, 39(3): 187-202. https://doi.org/10.11933/CSE2026179
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    The main bearings of large-scale wind turbines are continuously exposed to extreme working conditions for a long time. Under the long-term cyclic contact stress, the rolling elements and the bearing rings of the main shaft bearings will incur fatigue damage. This situation prompts the bearing raceways of the wind turbine main shafts to possess extremely high load-carrying capacity, fatigue resistance, and reliability, so as to deal with the complex loads during long-term operation. With the development of the laser technology field, the laser solid-state phase transformation technology has high action precision, a small heat-affected zone, and the capability to conduct solid-state phase transformation on the selected areas. It has become a suitable and effective method for improving the mechanical properties of wind turbine bearings. However, its influence on the subsequent service damage of the materials is still not clear. In order to explore the influence of laser solid-state phase transformation on the surface properties of the 42CrMo bearing raceway material and the initiation and propagation mechanism of cracks after phase transformation, the surface of 42CrMo steel is subjected to single laser solid-state phase transformation and laser-induction hybrid solid-state phase transformation treatments. The variation laws of the microstructure and hardness of the materials under different treatment processes are analyzed. Through the MJP-30A rolling wear and contact fatigue testing machine, the influence of different phase transformation methods on the rolling wear and contact fatigue properties of 42CrMo steel is compared and analyzed. The results show that during the single laser solid-state phase transformation process, due to the multi-pass laser overlapping, a hardened zone composed of martensite and a softened zone composed of tempered martensite are formed. The average surface hardness of the softened zone is 405 HV0.2, and the average surface hardness of the hardened zone is 562 HV0.2, which is 87.96% higher than that of the substrate. After the laser-induction hybrid solid-state phase transformation, the microstructure is entirely composed of martensite, and the average hardness is 724 HV0.2, which is 28.83% higher than that of the hardened zone in the single laser solid-state phase transformation. After the rolling contact wear under dry conditions, compared with the untreated specimen, the wear amounts of the specimen with single laser solid-state phase transformation and the specimen with laser-induction hybrid solid-state phase transformation are decreased by 93.20% and 96.14%, respectively. The higher the hardness of the material is, the thinner the thickness of the plastic deformation layer is. The thickness of the plastic deformation layer of the untreated specimen gradually decreases with the increase of the number of cycles, while the thickness of the plastic deformation layer of the laser solid-state phase transformation specimen shows no obvious change with the increase of the number of cycles. During the rolling contact process, when the plastic deformation exceeds the plastic strain limit, cracks begin to initiate. For the untreated specimen, the cracks propagate rapidly through the grains. After the cracks break through the plastic deformation layer, they bend and then continue to propagate in an almost horizontal direction. The surface cracks intersect, resulting in material spalling. At the same time, vertical cracks will be generated above the oblique cracks, which will also lead to material fracture and spalling. For the specimen with single laser solid-state phase transformation, none of the cracks break through the plastic deformation layer. In the softened zone, there are mostly delamination cracks, and the interlayer materials are prone to fracture under the action of the cyclic normal force. For the specimen with laser-induction hybrid solid-state phase transformation, after the cracks propagate with a trend parallel to the surface, they are fractured under the shear stress, forming spalling pits. After the laser solid-state phase transformation treatment, the wear resistance and fatigue resistance of 42CrMo steel are significantly improved. Among them, the improvement of the wear resistance and fatigue resistance of the laser-induction hybrid solid-state phase transformation is the most remarkable.
  • Wear Volume Prediction of Bearing Friction Pairs Based on the CSSA-BP Neural Network
    ZHANG Lixiu, XIAO Qingyi, LI Songhua, YIN Zhenyu, ZHENG Tongxiang
    China Surface Engineering. 2026, 39(3): 203-212. https://doi.org/10.11933/CSE2026180
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    The accurate prediction of bearing wear is critical for ensuring the reliability, lifespan, and performance of mechanical systems. However, the existing research on bearing wear prediction often suffers from limited accuracy and fails to account for the multi-factorial and nonlinear nature of the wear process. As bearings are subjected to complex conditions, such as varying loads, friction frequencies, and environmental temperatures, improving the precision of wear predictions under these conditions is essential for better performance evaluation and maintenance planning. This study addresses these limitations by exploring the multi-factorial and nonlinear relationships in bearing wear prediction and enhancing the predictive accuracy of existing models. To investigate the wear behavior of various bearing materials, this study employs the RTEC multifunctional friction-wear testing machine, which performs reciprocating sliding wear tests under dry friction conditions. Three different bearing pairs, Si3N4-Si3N4, Si3N4-GCr15, and GCr15-GCr15, were tested under various operational parameters, including wear duration, load, friction frequency, and ambient temperature. These conditions simulate real-world operational environments and provide a comprehensive dateset of friction and wear data, which is foundational for the predictive model. A novel prediction model based on a back propagation (BP) neural network optimized by an improved sparrow search algorithm (CSSA-BP) is proposed. This model incorporates input factors such as the bearing material type, wear duration, load, friction frequency, and ambient temperature to predict the wear amount of bearings under different conditions. The CSSA-BP model can improve the precision and robustness of wear predictions by accounting for the complex interactions between these multiple factors. The CSSA-BP model performance is evaluated using key statistical metrics. The determination coefficient (R2) was 0.980 1, indicating that the model explained 98.01% of the variance in the wear data. The mean squared error (MSE) was 0.046 7 and the mean absolute error (MAE) was 0.162 7, both of which suggested high accuracy and low error rates in the model predictions. These results demonstrate that the CSSA-BP model not only achieves a high degree of accuracy but also offers excellent fitting performance for predicting bearing wear under various operating conditions, provides valuable insights into the wear mechanisms of different bearing pairs, and offers an innovative approach to predicting wear using an optimized neural network model. The CSSA-BP model effectively enhanced the prediction accuracy and stability of wear estimates, which is crucial for improving the maintenance strategies and operational efficiency of bearings in industrial applications. By integrating multiple operational factors, the model surpasses the limitations of previous methods that rely on fewer input variables or simpler linear relationships. This study combines the sparrow search algorithm with a BP neural network, which allows the model to effectively handle the nonlinear and complex interactions among various input variables. The results indicate that the CSSA-BP model is a promising tool for predicting bearing wear, offering significant improvements in both prediction accuracy and computational efficiency compared to traditional models. This study provides a comprehensive and reliable method for predicting bearing wear across different operating conditions. The proposed CSSA-BP model contributes to a better understanding of bearing wear behavior and also holds significant potential for real-world applications in the predictive maintenance and performance optimization of bearings, ultimately extending the service life and reliability of mechanical systems.
  • Influence of Nitrogen Gas Flow Rate on Electrochemical and Tribological Properties of MoSiN Thin Films in Hank’s Solution
    AN Mingdong, QIAN Jianguo, YANG Cheng, MA Yue, WANG Qianzhi, TANG Chunbo, SHEN Jianxin, ZHOU Fei
    China Surface Engineering. 2026, 39(3): 213-225. https://doi.org/10.11933/CSE2026074
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    Titanium alloys are widely used as biocompatible materials for bone implantation and dental implant surgery; however, their low wear resistance can lead to implant failure. In addition, wear and tear may cause the release of harmful metal ions, such as vanadium and aluminum ions, from titanium alloys into the human body, thereby posing potential health risks. This issue can be effectively addressed by depositing a nitride film on the surface of titanium alloys via magnetron sputtering. Among various nitride films, MoN films have attracted considerable attention owing to their high hardness, favorable Young’s modulus, and relatively low coefficient of friction. Furthermore, Si3N4, a new generation of bioceramic materials, possesses advantageous radiographic, anti-infective, biocompatibility, and osseointegration properties, aside from the excellent characteristics typically expected of ceramic materials. Therefore, the preparation of MoSiN films on titanium alloy substrates presents a promising approach to mitigate the insufficient mechanical and tribological performance of titanium alloys. In this study, MoSiN thin films were deposited onto Ti-6Al-4V substrates and Si (100) wafers using magnetron sputtering under varying nitrogen flow rates. The results demonstrated that the nitrogen flow rate significantly influenced film composition, microstructure, mechanical properties, electrochemical behavior, and tribological performance. Specifically, as the nitrogen flow rate increased, the surface roughness and thickness of the films initially decreased and then increased. This trend was associated with the nitrogen partial pressure, nitrogen dissociation rate, and the phenomenon of target poisoning. At moderate nitrogen flow rates, the elevated nitrogen partial pressure reduced the flux of sputtered ions reaching the substrate surface. Although the energy enhanced surface mobility, the overall mobility was reduced, leading to larger cluster sizes and increased surface roughness. As the nitrogen flow rate further increased, protruding structures appeared on the film surface. However, the grain refinement effect induced by silicon nitride enhanced cluster densification, reducing both cluster size and surface roughness. Further increases in nitrogen flow caused the protruding structures to grow in size, resulting in a further increase in roughness. Additionally, a higher nitrogen flow rate increased the nitrogen content in the films and the proportion of MoN and MoSiNX phases, indicating an increase in metal-nitrogen covalent bonding and enhanced solid solution strengthening. Thus, both the film hardness and elastic-plasticity index improved progressively. The MoSiN-4 film exhibited the highest hardness, H = 12.96 ± 0.65 GPa, along with elastic-plasticity indices of H / E = 0.074 and H3/E2 = 0.071. Furthermore, the bonding strength of MoSiN films initially decreased and then increased, with the MoSiN-4 film achieving the highest bonding force of 6.45 N, indicating superior resistance to crack propagation and brittle spallation. Owing to the optimal combination of bonding strength, hardness, and elasticity, the MoSiN-4 film demonstrated the most favorable tribological properties, including the lowest and most stable coefficients of friction and minimal wear rates under both dry friction and Hank’s solution conditions. The wear rate of the MoSiN-4 film was (9.31 ± 1.3) × 10-5 mm3/(N·m) in dry environments and (2.96 ± 0.42) × 10-4 mm3/(N·m) in Hank’s solution. Additionally, the electrochemical properties of the MoSiN films in Hank’s solution were evaluated, revealing that the films exhibited the highest charge transfer resistance, Rct = 2.04 × 105 Ω·cm2, the lowest self-corrosion current density, Icorr = 5.56 × 10-8 A/cm2, and a stable anodic passivation region. These results indicated excellent corrosion resistance under static conditions. This study identified the optimal preparation conditions for fabricating MoSiN films with superior electrochemical and tribological properties. The influence of nitrogen flow rate on the film’s composition, microstructure, mechanical performance, electrochemical behavior, and tribological characteristics was comprehensively examined. The application of MoSiN thin films on titanium alloy surfaces effectively enhances their mechanical performance, thereby mitigating wear-related issues associated with titanium alloy implants in physiological environments and serving as a protective surface layer. These findings provide valuable reference data for future research on MoSiN-based biocompatible coatings.
  • First-principles Insight into Hydrogen Adsorption and Diffusion on the Ti3C2T2 MXene Surface
    MA Liqiu, ZHANG Jianbo, ZHOU Shengguo, CHEN Hao, LU Zhibin
    China Surface Engineering. 2026, 39(3): 226-238. https://doi.org/10.11933/CSE2026321
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    With the rapid advancement of industries such as aerospace, shipbuilding, high-speed rail, petroleum, and chemical engineering in China, the demand for high-strength metallic materials has increased significantly. However, when these materials are exposed to hydrogen-containing environments, they are susceptible to a unique form of fracture failure known as hydrogen embrittlement. The application of hydrogen barrier coatings on metal surfaces offers a promising approach to preventing or delaying hydrogen ingress, thereby mitigating embrittlement and enhancing material durability. As a result, hydrogen-induced degradation remains a critical challenge for protective coatings used in hydrogen-rich environments, particularly in the petroleum and chemical sectors. In this context, two-dimensional (2D) nanomaterials have attracted considerable scientific and engineering interest due to their excellent structural and physicochemical properties. Their high surface-area-to-thickness ratios differ markedly from those of conventional 3D bulk materials. MXenes, a class of emerging 2D nanomaterials, have attracted widespread attention due to their tunable mechanical and electrical properties, excellent hydrophilicity, high charge mobility, outstanding flexibility, and good compatibility with various matrices. These materials are typically synthesized by selectively etching the “A” layers from bulk MAX phases (ternary carbides and nitrides), followed by exfoliation, using etchants such as LiF-HCl, HF, and HF salts. As either standalone coatings or nano-fillers, MXenes have garnered increasing interest in the field of metal surface protection. Numerous studies have demonstrated that MXenes can effectively inhibit the penetration of corrosive species owing to their well-defined two-dimensional structure and strong physical barrier effect. Moreover, these characteristics endow the MXene-based material with excellent protective performance. Nevertheless, theoretical investigations into the ability of MXenes to inhibit H diffusion, particularly with consideration of surface functionalization, remain limited. Therefore, elucidating the interaction mechanisms of H on MXene surfaces at the micro-electronic scale is of significant importance. In this study, the adsorption and diffusion behaviors of H on pristine Ti3C2 and functionalized Ti3C2Ti2 (-F/-O/-OH) surfaces were systematically investigated using first-principles calculations. By analyzing adsorption configurations, adsorption energies, differential charge densities, electronic density of states, and diffusion energy barriers, the mechanisms governing H diffusion inhibition were clarified from both thermodynamic and kinetic perspectives. The results indicate that the adsorption energies of H on functionalized Ti3C2F2, Ti3C2O2, and Ti3C2O2H2 are significantly higher than those on pristine Ti3C2. The adsorption energies of H on vacancy V-Ti3C2F2, V-Ti3C2O2, and V-Ti3C2O2H2 follow a similar trend to that observed for V-Ti3C2, with the highest adsorption energy occurring on the F-functionalized Ti3C2F2 surface. The diffusion energy barrier of an H atom on the pristine Ti3C2 surface is slightly lower than that on the vacancy-containing V-Ti3C2 surface. Furthermore, the diffusion energy barriers of H on V-Ti3C2O2 and V-Ti3C2O2H2 surfaces are significantly higher than those on Ti3C2O2 and Ti3C2O2H2 surfaces without vacancies. However, the diffusion energy barriers of H atoms on both Ti3C2F2 and V-Ti3C2F2 are negative, indicating their relatively poor effectiveness in inhibiting H diffusion. The diffusion energy barriers of H atoms on Ti3C2O2 and Ti3C2O2H2 surfaces are significantly increased compared to those on pristine Ti3C2, with the diffusion energy barrier reaching a relatively high value on the Ti3C2O2 surface. In particular, the diffusion energy barrier of H on the V-Ti3C2O2 surface attains a maximum value in the presence of vacancies, which is much higher than that on the Ti3C2O2 surface without vacancies, demonstrating an effective blocking effect on H diffusion. These findings provide an important theoretical basis for the design of MXene-based protective materials in hydrogen-containing environments.
  • Effect of Electrodeposition Time on Electrochemical Properties of Mn-MOF Coating on Aluminum Alloy Surface
    XIE Feng, YUE Hao, ZHAO Rui, ZHANG Yu, SHANG Wei, JIANG Jiqiong, WEN Yuqing
    China Surface Engineering. 2026, 39(3): 239-248. https://doi.org/10.11933/CSE2026064
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    Metal-air batteries have attracted extensive attention due to their exceptional energy density, large capacity, and low cost. Among them, aluminum-air batteries, as a new type of energy storage equipment with great potential, have important application prospects in future energy storage fields. However, aluminum-air batteries face a major obstacle in practical applications: the hydrogen evolution reaction of the anode leads to low anode utilization, which considerably affects the performance and life of the battery. To solve this problem, this study aims to inhibit hydrogen evolution by preparing a metal-organic framework (Mn-MOFs) coating on the surface of an aluminum alloy anode to improve the electrochemical performance and anode utilization of aluminum-air batteries. In this study, a Mn-MOF coating was prepared on the anode surface of an aluminum alloy via one-step electrodeposition. First, the microstructures of the Mn-MOF coatings were analyzed in detail using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Subsequently, the corrosion resistance of the coating and its effect on the anode utilization were evaluated using electrochemical and hydrogen evolution corrosion tests. The effects of different deposition times (10, 20, and 30 min) on the electrochemical properties of Mn-MOF coatings were studied. To further understand the anti-corrosion mechanism of the Mn-MOF coating, the study combined quantum mechanical calculations to simulate the interaction between the coating and the aluminum anode and its inhibitory effect on the hydrogen evolution reaction. The experimental results showed that when the deposition time of the Mn-MOF coating was 20 min, the aluminum-air battery exhibited the best electrochemical performance. SEM and EDS analyses showed that the coating layer had a dense structure and uniformly covered the aluminum alloy surface, which effectively prevented the OH- in the electrolyte from directly contacting the aluminum alloydirectly. FT-IR and XPS analyses confirmed the successful preparation of the Mn-MOF coating layer and revealed its chemical composition and valence bond states. Electrochemical tests showed that the Mn-MOF coating significantly reduced the hydrogen evolution rate of the anode, thereby improving its utilization rate. A hydrogen evolution corrosion test showed that the coating significantly extended the lifetime of the Al alloy anode. The quantum mechanical calculation results show that, owing to its unique chemical structure, when the Mn-MOF membrane is consumed, the (-COO-) in the aromatic acid can react with Al3+ in solution to form the RCOO-Al complex, which is deposited on the electrode surface, inhibiting the diffusion of intermediate products into the solution. This effectively inhibits the hydrogen evolution reaction. This can significantly improve the electrochemical performance and anode utilization of Al-air batteries. In addition, this study applied a Mn-MOF coating layer to the anode protection of aluminum-air batteries, and through systematic experiments and theoretical analysis, through a series of experiments and simulations, the anti-corrosion mechanism of the Mn-MOF coating layer was discussed, which opens up a new method for the surface treatment of metal-air batteries and provides an important theoretical basis and technical support for the performance optimization of metal-air batteries in the future.
  • Modeling Sealing Rubber Contact Surface with Surface Roughness Characteristics
    FU Hailong, YAO Aoxiang, ZOU Longqing, ZHU Jialei, CHEN Jinghao
    China Surface Engineering. 2026, 39(3): 249-261. https://doi.org/10.11933/CSE2026181
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    Numerical simulation of seal rubber contact friction is crucial in investigating seal failure mechanisms, and the accuracy of the seal contact surface modeling method is essential for reliable analysis. Traditional modeling approaches often suffer from high testing costs and insufficient precision in surface reconstruction, thereby limiting their effectiveness in practical applications. To address these challenges, this study proposes a novel sealing rubber contact surface modeling method that incorporates surface roughness characteristics. By integrating the 3D W-M fractal theory with the microconvex body theory, a mathematical model of the random height of the rough surface contour was established using surface roughness parameters as the initial input. This model included the fractal dimension and characteristic scale parameters to better characterize the complex surface topography of the sealing rubber. The generated rough surface contour was converted into a three-dimensional point cloud dataset, which was then imported into the UG software to form a coordinate point cloud matrix. A structured modeling approach was employed to sequentially construct points, surfaces, and solid bodies, resulting in a detailed 3D contact model of the rough surface of the sealing rubber. To evaluate the effectiveness of the proposed method, numerical simulations were conducted under applied loads ranging from 0 to 4 MPa for rubber sealing pairs with different surface roughness levels. The simulation results were compared with the experimental data to validate the reliability of the modeling approach. The analysis successfully determined the real contact area, contact state, and distribution characteristics of the contact stress, thereby providing valuable insights into the contact behavior of rough sealing surfaces. This study validates that the proposed method can effectively capture intricate roughness-induced contact variations, which are critical for understanding sealing performance and failure mechanisms. The proposed modeling technique relies solely on initial surface roughness parameters, eliminating the need for high-precision surface measurement instruments. By employing mathematical modeling and software-based surface reconstruction, this approach significantly reduces the measurement costs and complexity associated with specimen characterization. Moreover, the proposed method offers enhanced adaptability, allowing the analysis of diverse surface roughness conditions without requiring extensive experimental measurements. This study contributes to the field by developing an innovative contact surface modeling approach that integrates 3D W-M fractal and microconvex body theories, thereby enabling a more accurate representation of rough sealing surfaces. A structured modeling workflow was introduced to transform rough surface parameters into 3D point-cloud data, facilitating high-fidelity digital reconstruction. The proposed method was validated through numerical simulations and experimental comparisons, demonstrating its reliability in predicting real contact areas and contact state distributions under varying load conditions. By eliminating the need for high-cost surface-measurement equipment, this approach presents a cost-effective and practical alternative for engineering applications. This study presents an innovative surface modeling method for sealing rubber contact analysis that provides a more accurate and cost-efficient alternative to traditional modeling techniques. The ability to simulate and analyze rough surface contact characteristics without direct high-precision measurements enhances their applicability in both research and industrial settings. Future work will further refine the model by incorporating additional material properties and exploring its applicability to broader sealing performance analyses.
  • Effects of Deposition Temperature on Microstructure and Mechanical Property of DLC Coatings
    ZHAO Yanhui, GUO Zhaoxin, KONG Hui, YU Zeyang, YU Xiaoming, LIU Changchun
    China Surface Engineering. 2026, 39(3): 262-272. https://doi.org/10.11933/CSE2026065
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    Medical-grade 316L stainless steel is widely used in artificial joint implantation, cardiovascular disease treatment, and various surgical tools owing to its excellent mechanical properties and easy processing and shaping. However, 316L stainless steel is prone to pitting corrosion in the complex fluid environment of the human body, thereby leading to inflammation and implant failure. In addition, its surface wear resistance is poor, and long-term wear further exacerbates the degradation of its surface properties. Depositing wear- and corrosion-resistant coatings, such as diamond-like carbon (DLC) coatings, on the surfaces of these components is one of the effective ways to solve this problem. Arc-enhanced glow discharge (AEGD) technology, which is a new technology developed in recent years, is generally used for ion sputtering and cleaning of the substrate/workpiece surface before coating. In this study, AEGD was used as an ion source by introducing a carbon-containing gas, thereby generating a carbon-containing plasma, which was then deposited onto the substrate surface to form a hydrogen-containing DLC coating. Using methods such as scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy, nanoindentation, friction and wear testing, and electrochemical testing, the effects of deposition temperature on the coating structure, mechanical properties, friction properties, and corrosion resistance were studied. M2 high-speed steel and 316L stainless steel were selected as the base materials for the experiment, with dimensions of Φ 20 mm × 3 mm. After grinding with sandpaper and mirror polishing, all the base materials were ultrasonically cleaned in acetone and anhydrous alcohol solutions for 15 min, then dried, and placed on the workpiece table of the coating equipment. The target material was high-purity Cr. When the vacuum chamber was heated to 170 ℃, the AEGD ion source was turned on, and high-purity argon gas was introduced at a pressure of 0.4 Pa. A DC bias of -200 V was applied to the substrate, and high-energy argon ions generated by AEGD were used to bombard and sputter the substrate surface to remove the oxide layer and pollutants on it. The objective was to improve the film/substrate bonding force and further enhance the bonding force between the DLC coatings and steel substrate. Before depositing a coating, a Cr bonding layer and CrC transition layer were deposited on the substrate surface using a Cr target. Then, in order to investigate the effects of deposition temperature on the structure and properties of DLC coatings, the vacuum chamber temperatures were controlled at 170, 250, 350, and 450 ℃, respectively, and the coating time was 60 min. The results showed that the DLC coatings prepared at different deposition temperatures generally exhibited smooth and flat surfaces. Using high-magnification SEM, no macroscopic particles were observed in the coatings prepared at lower deposition temperatures (170 ℃), and the surface roughness was lower. The coatings prepared at higher deposition temperatures (250, 350, 450 ℃) had macroscopic particles and higher surface roughness. This indicates that a lower-deposition-temperature preparation process suppresses the problem of large particles caused by “target poisoning” and can achieve a regular surface morphology. The content of sp3 hybridized bonds in the internal structures of the DLC films prepared at lower deposition temperatures was high. As the deposition temperature increased, the content of sp3 hybridized bonds gradually decreased, thereby leading to graphitization. The coating prepared at a deposition temperature of 170 ℃ exhibited excellent mechanical properties, with the hardness and elastic modulus reaching maximum values of 61 GPa and 414 GPa, respectively. The hardness remained around 10 GPa under other temperature parameters. In addition, the wear resistance of the coating prepared at 170 ℃ was improved, and its wear rate was reduced by six times compared with that of the substrate. The coating prepared at 250 ℃ had the best corrosion resistance, and its self-corrosion current density was reduced by about eight times compared with that of the stainless steel substrate.
  • Tribological Properties of Phosphate Ionic Liquid as Lubricant for Steel/copper Contact
    HU Shuai, HAN Chaoyan, ZHOU Zheng, YAO Huan, SUN Yuchen, ZHANG Chaoyang, WANG Xingwei, LI Feizhou, Mohamed Kamal Ahmed Ali, YU Qiangliang
    China Surface Engineering. 2026, 39(3): 273-284. https://doi.org/10.11933/CSE2026167
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    In view of the friction and wear phenomenon of copper alloy mechanical parts during operation, four kinds of phosphate amine salt ionic liquids (P4-12, P8-12, P4N1116, P8N1116) were synthesized and added to the base oil 150SN as an additive at a mass fraction of 1%. Compared with 150SN, the lubrication performance of steel/copper friction pair was explored. The thermal decomposition temperature of the five lubricants was tested by a synchronous thermal analyzer. It was found that the thermal decomposition temperature of 150SN could be significantly increased after the addition of ionic liquids, and the initial thermal decomposition temperature exceeded 240 ℃, with high thermal stability. By comparison, when the anions were the same, the increase of cationic alkyl chain could increase its thermal decomposition temperature. Among them, the initial thermal decomposition temperature of 1% P8N1116 with longer alkyl chain was the highest, reaching 266.232 ℃. The measurement of viscosity data showed that the addition of ionic liquids had little effect on the viscosity-temperature performance of 150SN. The tribological properties of 150SN on steel/copper friction pairs were evaluated by SRV-IV fretting friction and wear tester and non-contact three-dimensional surface profiler. It was found that the addition of ionic liquids could improve the anti-friction and anti-wear properties of 150SN at room temperature and high temperature. Among them, P4N1116 containing longer alkyl chain cations and shorter alkyl chain anions had the most significant effect on improving the tribological properties of 150SN. The wear volumes at room temperature and high temperature were reduced by 92.8% and 58.8%, respectively, from the perspective of alkyl chain. Comparing the experimental results of ionic liquids with the same cationic and anionic alkyl chains, it can be found that the improvement of tribological properties of cationic long alkyl chains is better than that of anionic long alkyl chains, and the anti-friction and anti-wear properties of cations with long alkyl chains are better than those of cations with short alkyl chains. The long-term grinding experiments of 150SN and 1% P4N1116 at room temperature and high temperature for 1 h were carried out. It was found that the lubrication performance of ionic liquids did not change significantly under long-term working conditions. The friction experiments under variable load, frequency conversion and variable temperature conditions were carried out on the two lubricants. The experimental results show that the ionic liquid can adapt to the complex working conditions and improve the tribological performance of 150SN. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology of the wear scar and the elemental composition of the wear scar surface to evaluate the lubrication mechanism. The results show that the wear scar becomes smaller and the surface becomes smoother after the addition of ionic liquid lubrication. The reason is that during the friction process, the physical adsorption film formed by the adsorption of anions and cations in the ionic liquid and the reactive elements N, P, and O react with the copper plate to form a tribochemical reaction film containing phosphate and nitrogen-containing copper complex, which effectively protects the surface of the friction pair and reduces the wear in the friction. Therefore, the lubrication effect of 150SN is improved, and the excellent tribological properties of the synthesized ionic liquid are shown. It is of great significance to study the lubricant of copper alloy mechanical parts, reduce the friction and wear phenomenon during the operation of the equipment, and prolong the service life of the equipment.
  • Preparation and Tribological Properties of Nano-alumina Modified Three-layer Composite Material
    ZHANG Guotao, LU Zheng, HUANG Shan, YIN Yanguo, LI Qilong, LI Congmin
    China Surface Engineering. 2026, 39(3): 285-293. https://doi.org/10.11933/CSE2026182
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    Three-layer self-lubricating composites are commonly used as friction materials in mechanical transmission equipment. The polymer on the surface of a three-layer composite material usually has poor wear resistance, which is a key factor that restricts its service performance and service life. For example, sliding bearings made of three-layer composite materials typically operate under high loads and continuous running conditions, under which prolonged friction leads to the wear of the bearing materials and thereby affects their performance and lifespan. Therefore, improving the overall mechanical properties and tribological performance of sliding bearing materials has become an urgent issue in engineering. To address this challenge, this study adopted a high-temperature rolling technique to prepare a novel polytetrafluoroethylene (PTFE)-Cu-steel three-layer composite self-lubricating bearing material. The composite material used steel as the substrate, copper as the intermediate layer, and PTFE as the surface layer to achieve high strength and self-lubrication. Additionally, nano-alumina (Al2O3) particles were introduced to fill and modify the surface PTFE material to further enhance its mechanical and tribological properties. Because of their small size, large specific surface area, and high surface energy, nanomaterials can significantly improve the strength, hardness, and wear resistance of composite materials. A material-testing machine was used to test the mechanical properties of the composite material and comprehensively evaluate its performance. A tribological tester was used to study friction and wear properties. Microscopic detection techniques were used to analyze the surface morphology and structural changes after wear. The experimental results demonstrate that the introduction of nano-alumina significantly enhances the mechanical and wear resistance properties of the composite material. When the nano-alumina content was 0.5%, the surface hardness of the composite material increased by 17.9%, and the bonding strength improved by 27.7%. Furthermore, stepwise tribological experiments revealed that the friction coefficient of a three-layer composite material containing 0.5% nano-alumina decreased by 16.19% and the wear scar depth was reduced by 10.86%. These results suggest that the modified composite material can effectively reduce friction and wear over long-term use, which extends service life. Further research indicated that nano-alumina promotes the growth of a transfer film on the counterface through chemical reactions during friction. The transfer film formed a protective layer to shorten the running-in period and extend the stable wear period. Additionally, the inclusion of nano-alumina reduced the friction coefficient during the stable wear period by 25%. Overall, the nano-alumina-modified PTFE-Cu-steel three-layer composite self-lubricating bearing material developed in this study exhibited significant improvements in terms of both mechanical and tribological properties. This study will support the future development of self-lubricating bearing materials and offer innovative solutions to tribological problems in various engineering fields.
  • Effect of Ultrasonic Pulse Current on Microstructure and Properties of Arc Additively Manufactured Ti-6Al-4V Titanium Alloy
    ZOU Enyu, HAN Guofeng, SHI Chengcheng, HUANG Xiangyuan, WANG Wenyu, ZHU Sheng, NIU Zongwei
    China Surface Engineering. 2026, 39(3): 294-305. https://doi.org/10.11933/CSE2026168
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    Ti-6Al-4V titanium alloys have high application prospects in aerospace, weapons and equipment, large ships, and other fields owing to their excellent properties such as high specific strength and strong environmental adaptability. However, other inherent characteristics such as poor thermal conductivity, high chemical activity, and high deformation resistance, cause complex components to face long processing cycles, high manufacturing costs, low material utilization, poor manufacturing flexibility, and difficulties when processed by traditional casting, welding, and forging methods. Although the Ti-6Al-4V titanium alloy was manufactured by the conventional wire arc additive manufacturing (WAAM) method, it solved the problems of difficult processing and long processing time for large and complex components; however, most samples showed coarse columnar crystal structures and defects such as pores, resulting in reduced mechanical properties. To solve these problems, an ultrasonic pulse current was introduced based on the conventional WAAM process. On the one hand, by superimposing the ultrasonic current on the base current, a lower welding current than the conventional arc additive can be used in processing, thereby reducing the heat input in the overall process. However, the ultrasonic pulse current promotes the contraction and concentration of the arc, enhances the arc force, and stirs the molten pool to a certain extent, thereby promoting the formation of equiaxed crystals. Finally, based on conventional tungsten inert gas arc welding, the ultrasonic pulse current is superimposed, and the microstructure and performance of Ti-6Al-4V titanium alloy arc additive manufacturing are regulated by adjusting the pulse frequency of the ultrasonic pulse current. First, a single-pass double-layer pre-experiment was conducted. After the pre-experiment was completed, wire cutting equipment was used for cutting and sampling, and the obtained metallographic specimens were polished using 220#, 600#, 1 200#, 2 000#, and 3 000# sandpapers, followed by mechanical polishing. After preliminary mechanical polishing, electrolytic polishing was used for final sample preparation. After electrolytic polishing, Kroll’s reagent was used for etching for 15 s. An optical microscope was used to observe the macro- and microstructures of the metallographic samples. After obtaining the optimized test parameters, a single-channel multilayer straight-wall printing test was conducted. The metallographic preparation method for the single-channel multilayer experiment was consistent with that of the single-channel double-layer pre-experimental method. The samples were subjected to scanning electron microscopy, room-temperature tensile mechanical property tests, and tensile fracture scanning electron microscopy analysis. The results show that the epitaxial growth of the Ti-6Al-4V primary β grains are improved by introducing ultrasonic pulse current, and the metallographic analysis of the pre-experiment clearly shows that the columnar crystals are broken into equiaxed crystals. In the pulse frequency range of 20-30 kHz, the microstructure of the Ti-6Al-4V titanium alloy is evenly distributed and composed of a fine basketweave structure, with the highest yield strength and tensile strength of 890 and 998 MPa, respectively, which are 8% and 6% higher than those of traditional arc additive manufacturing. The lowest elongation is 4.3% and the highest is 12.3%, which is an increase of approximately 60%. In the pulse frequency range of 20-30 kHz, the microstructure of the tensile fracture is a mixed morphology of dimples and tear edges; the dimples are larger and deeper, whereas the fracture morphology microstructure without adding ultrasonic pulse current has smaller and shallower dimples, and obvious pores and holes can be seen from the front fracture morphology. However, with an increase in pulse frequency, the orientation of the basketweave organization becomes disordered, and the α lath becomes coarse. By applying ultrasonic pulse current, defects such as pores are effectively eliminated, and the elongation is significantly improved.
  • Influence of Polyamide Particles on the Lubrication Properties of Lithium-based Lubrication Grease
    LI Chuan, TAN Xu, CHEN Yijun, HU Enzhu
    China Surface Engineering. 2026, 39(3): 306-314. https://doi.org/10.11933/CSE2026169
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    With the continuous advancement of science and the increasing complexity and diversification of high-end equipment operating conditions, higher demands have been imposed on the performance of lubricating greases. Functional additives have emerged as effective materials to enhance the performance of traditional lubricants. Owing to the insufficient lubrication performance of traditional lubrication grease for the critical tribopair, equipment life is shortened, which may cause accidents under extreme conditions. Therefore, developing high-performance lubricants is important. Tribological studies on organic polymerized microspheres as functional additives are relatively scarce. Therefore, in this study, a polyamide (PA6) was added to lithium-based grease (LBG), and its effects on the lubrication properties of the grease were investigated. The findings of this study open new avenues for developing high-performance greases and provide valuable insights for optimizing lubricant formulations through polymeric material incorporation. PA6 microparticles were used as lubricant additives, and their effect on the tribological properties of lithium-based grease was investigated using an HSR-2M high-speed reciprocating tribometer. The physicochemical properties of the polymer particles were characterized and analyzed using thermogravimetric analysis/differential scanning calorimetry (TG/DSC) and Fourier-transform infrared (FTIR) spectroscopy. The PA6 microspheres material exhibited high thermal stability, with a thermal decomposition temperature above 400 ℃, which generally meets the temperature requirements of lubricating grease under typical operating conditions. In this experiment, the temperature was set to 24 ℃ to test the performance of non-crystalline PA6 material as a lubricating grease additive. The wear-scar areas of the steel balls were determined through systematic characterization and analysis using field-emission transmission electron microscopy (FETEM) and other analytical techniques. The surface morphology and elemental distribution of the friction pair interface were analyzed using scanning electron microscopy (SEM) and 3D laser microscopy. The chemical valence states of the elements at the friction interface were characterized using X-ray photoelectron spectroscopy (XPS) to elucidate the friction and wear mechanisms. The results show that the PA6 particles have a spheroid structure with diameters in the range of 40-60 nm. The TG/DSC results indicate that the decomposition temperatures of the PA6 particles are 265 and 417 ℃ at 5wt.% and 20wt.% particle contents, respectively. The highest decomposition temperature was 462.4 ℃. The glass transition temperature of PA6 is 213.2 ℃, and the melting point is 403.1 ℃. In the FTIR spectra, the peak at 3 311.9 cm-1 is attributed to the N-H stretching vibration of the amine group, the peak at 1 631.7 cm-1 is attributed to the C=O stretching vibration of the amide group, and the peak at 1 262.1 cm-1 is attributed to the C-N stretching vibration. The peaks at 2 929.8 and 2 855.9 cm-1 are ascribed to -CH2- and -CH3 stretching vibrations, while those at 1 461.2 and 1 352.4 cm-1 correspond to -CH3 and -CH2- bending vibrations. As additives, PA6 microspheres can significantly improve the lubricating performance of Li-based greases. Within a certain range, as the mass fraction of the PA6 microspheres increased, the effect of improving the performance of the lithium-based grease first increased and then decreased; the optimal additive concentration was 0.25wt.%. When the other experimental conditions were the same, the average friction factor of the PA6+LBG grease at a load of 20 N and speed of 50 mm/s was the lowest (0.226)—57.4% lower than that of pure LBG (0.530)—and the wear volume of the lower plate was reduced by 74.7%. During the friction process, the transfer film formed by the PA6 microspheres on the surface of the lower plate effectively reduced the direct contact of the friction pair, demonstrating good anti-friction and wear resistance.
  • Effect of Ni Content on the Microstructure and Wear Behavior of FeCrNi Laser Cladding Layer on Frog Steels Used for Heavy Haul Railways
    DONG Yiting, XU Xiaojun, GAO Yu, LI Hao, ZHU Minhao
    China Surface Engineering. 2026, 39(3): 315-325. https://doi.org/10.11933/CSE2026066
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    Frog steel, a key component of railway turnouts, is often susceptible to wear damage during real-life running processes, resulting in significant economic losses. At present, welding repair technology is generally used to fix wear damage; however, it suffers from drawbacks such as large welding heat-affected zone and carbide precipitation, which can lead to ductility reduction. To overcome this limitation, this study adopted laser-cladding technology to produce laser-cladding layers with different Ni contents (2.5%, 5%, and 9.5%) on the surface of high-manganese frog steel. Advanced micro-characterization techniques, such as scanning electron microscopy (SEM), electron probe X-ray microanalysis (EPMA), focused ion beam transmission electron microscopy (FIB-TEM), 3D-white-light interferometry, and X-ray diffraction (XRD), were utilized to observe the microstructural features and evolutions as well as the phase transformation. Tangential reciprocating sliding wear tests were employed to systematically reveal the wear resistance of the cladding layers with different Ni contents under different loading conditions (25, 30, and 35 N). The microstructural features of all cladding layers, microstructural changes during the wear process, and their impact on the wear performance are systematically discussed. The results showed that the microstructures of all the laser cladding layers were composed of eutectic and dendritic structures, in which the eutectic structure exhibited a continuous network within the dendritic structure. The dominant phase structures of the cladding layers are face-centered cubic (FCC) and body-centered cubic (BCC). There was a difference in the nanohardness between the eutectic and dendritic structures, presenting a combination of soft and hard phases. With increasing Ni content, the dominant phase changed from BCC to FCC, and both the hardness and its rangeability decreased. The wear results demonstrated that the cladding layer with 2.5% Ni content had the best wear resistance with the highest hardness. The cladding layer with 5% Ni content, given the continuous hard-phase network encapsulating the soft phase, also demonstrated good wear resistance despite its lower hardness. Both wear mechanisms were the main types of abrasive wear. In contrast, the cladding layer with 9.5% Ni exhibits the worst wear resistance, and the resulting wear mechanisms are primarily abrasive wear and severe delamination. Cross-sectional observations of the worn scars revealed that cracks tend to initiate and propagate along the eutectic-dendritic boundaries during wear due to the large hardness difference between eutectics and dendrites, ultimately causing fragmentation of the eutectic structure. The laser cladding layer with 9.5% Ni has a more evident and severe plastic deformation layer on the subsurface than the other laser cladding layers. Meanwhile, the transformation from FCC to BCC (TRIP effect) occurred for each cladding layer, and the degree of transformation was dependent on the Ni content, which is crucial in the stability of the FCC phase in the eutectic structure and influenced the wear resistance of the laser cladding layer. Based on the understanding of the microstructural transformation of the laser cladding layer during the wear process and its influence on wear resistance, a correlation between the laser cladding layer composition and microstructure wear resistance was established. These findings provide a theoretical foundation for designing the chemical composition of laser-cladding materials and their engineering applications on the surface of frog steel.
  • Numerical Study of Full-scale Coupling Erosion Mechanism of Ring, Rotor and Ni-graphite Coatings
    WANG Xinran, SUN Youbei, WANG Wei, DING Juanqiang, GONG Xiufang, LIU Senhui, LI Chengxin, LI Changjiu
    China Surface Engineering. 2026, 39(3): 326-342. https://doi.org/10.11933/CSE2026170
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    In the context of gas turbine technology, the erosion behavior of nickel-graphite sealing coatings on holding rings under service conditions presents significant challenges for experimental measurements. The unique operational environment of gas turbines, characterized by high temperatures, speeds, and pressures, complicates the experimental observation processes, making them time-consuming and labor-intensive. Therefore, computational simulation methods are employed to effectively analyze various operational parameters during service. This study investigates the thermal and mechanical behavior of the nickel-graphite coating system. Full-scale coupled numerical heat transfer calculations are performed, focusing on the entire holding ring, blades, rotor, and coating structure. This study aims to establish a detailed understanding of the thermal stresses and erosion rates associated with different thickness ratios of the coating layers, which involves developing a full-scale thermomechanical coupling model and a complete simulation model for the compressor-holding ring, rotor, and blades. These models are designed to accurately represent complex interactions between components under operational conditions. The numerical simulations are performed using advanced computational techniques, enabling analysis of thermal stress distributions and erosion rates across the coating layers. The results indicate that when the thickness ratio of the nickel-coated graphite surface layer to the NiAl substrate layer was set at 1∶1, the minimum thermal stress was 0.7 MPa, whereas the maximum was 72.96 MPa. Furthermore, when the thickness ratio was adjusted to 2.73∶0.27, with a surface-layer thickness of 2.73 mm, the maximum thermal stress on the coated surface increased to 74.51 MPa. These findings highlight the critical influence of coating thickness on thermal stress distribution, which is essential for understanding the durability and performance of the coatings under high-stress conditions. Additionally, the relationship between the rotational speed of the blades and the erosion rate of the sealing coating was explored. It was found that the erosion rate was negatively correlated with blade rotational speed. Specifically, at a blade rotational speed of 350 m/s, the maximum erosion rate of the sealing coating was calculated to be 2.863 × 10-5 kg/(s·m2). In this study, from a numerical simulation perspective, the influence of the surface-to-base layer ratio in the seal coating system on the seal coating performance, and the effect of linear velocity on the nickel-graphite coating on the inner wall of a gas turbine casing, were investigated.
  • Effect of Methane Flow Rate on Microstructure and Tribological Properties of Boron Carbide-based Thin Films
    ZHANG Xinyun, WANG Ning, JIANG Chengyan, WANG Peng, ZHAO Xiaoyu, PANG Xinru, CHAI Liqiang, GUO Junde
    China Surface Engineering. 2026, 39(3): 343-352. https://doi.org/10.11933/CSE2026183
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    Boron carbide (B4C) ceramics are characterized by a high melting point, high hardness, low density, and other excellent properties. Moreover, the presence of 10GB in B4C has neutron absorption properties, and it is commonly used to fabricate control rods in reactors. The preparation of coatings is important for reducing friction and wear between mechanical components to extend their service life. Coating preparation technologies include chemical vapor deposition, physical vapor deposition (PVD), and other plasma-based techniques. Among these, direct-current and radio-frequency magnetron sputtering in PVD have been successfully commercialized on a large scale because of their simple process and low-temperature characteristics. To improve the performance of coatings, deposition parameters such as bias voltage, gas flow rate, vacuum level, and deposition temperature can be adjusted during the coating preparation process, leading to significant changes in the microstructure, mechanical properties, and tribological properties of the films. This study investigated the deposition of a chromium transition layer on a W18Cr4V substrate, followed by the preparation of B4C and diamond-like carbon (B4C-DLC) coatings using direct current magnetron sputtering in an argon gas atmosphere with the introduction of methane (CH4) gas. Different flow rates of CH4 gas were introduced during the coating deposition process to prepare B4C-DLC coatings with varying properties. The microstructure and chemical structure of the films were characterized using field-emission scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. A comparative analysis of the tribological properties of the prepared films was conducted using a CSM standard friction and wear tester. The transfer films on the ball after friction tests and the wear tracks were characterized to investigate the effects of the CH4 flow rate on the microstructure and tribological properties of B4C nanocoatings, as well as the frictional chemical reactions occurring during friction. The results indicate that the CH4 gas flow significantly affects the surface morphology, thickness, chemical structure, and tribological properties of the films. The deposition rate of the films gradually increased with increasing CH4 gas flow rate, with film thickness increasing from 1.4 μm at 0 mL/min to 2.2 μm at 20 mL/min CH4 gas flow. The surface roughness initially decreased and then increased with CH4 gas introduction. XPS analysis showed that the carbon content inside the films increased from 55% to 86% with increasing CH4 gas flow, accompanied by an increase in the proportion of C-C bonds, forming more carbon-rich carbides. When the CH4 flow rate was ≥10 mL/min, the Raman spectra of the films exhibited typical DLC lubricating phase characteristic peaks, indicating successful preparation of B4C-DLC films. Moreover, the ID /IG ratios of the films gradually increased with increasing CH4 gas flow rate. Friction results demonstrate that the friction factor of B4C films fluctuates at approximately 0.8-0.9, with a wear rate of 4.47×10-5 mm3·N-1·m-1. Stable transfer films did not form after friction tests, and the wear tracks exhibited wide and plowed characteristics. When the CH4 flow rate was in the range of 15-20 mL/min, the friction factor of the films decreased to 0.05, and the wear rate decreased by two orders of magnitude compared to the case without CH4 flow. Stable transfer films were formed on the ball, with shallower and narrower wear tracks. The main reason for the improved tribological properties of B4C-DLC nanocomposite films was the introduction of the DLC lubricating phase. Further XPS analysis of the wear tracks after the friction of the B4C-DLC films revealed frictional chemical reactions occurring at the sliding interface. The improvement in their tribological properties was attributed to the synergistic effect between the DLC lubricating phase and the frictional chemical reaction products (B2O3). Therefore, DLC films with good lubrication properties were successfully prepared by regulating the CH4 flow rate, which enriched the theoretical study of DLC-lubricated coatings.
  • Influence Mechanism of Metal Solid-state Phase Transformation on Residual Stress Formation during TBM Cutter Ring Heat Treatment
    WANG Haoping, MO Jiliang, ZHANG Mengqi, SUN Ruixue
    China Surface Engineering. 2026, 39(3): 353-364. https://doi.org/10.11933/CSE2026171
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    Heat treatment plays a decisive role in determining the distribution and magnitude of the final residual stress during the forming process of a cutter ring in a tunnel boring machine (TBM). If issues such as toughness mismatches, microstructural defects, or an uneven stress distribution occur during the forming process, the risk of cutter ring failure due to chipping or cracking increases significantly. Such failures not only cause uneven wear of the cutter ring but may also lead to jamming of the cutter head, severely affecting the efficiency of TBM construction. To address this problem, this study develops a high-precision stress prediction model for the cutter ring to investigate the formation and evolution of residual stresses. The aim of this study is to optimize the heat treatment process, achieve a more reasonable stress distribution, and reduce the risk of abnormal failures. A coupled numerical model of the temperature, microstructure, and stress fields is established for the heat treatment process of a TBM cutter ring. This model analyzes the microstructural and stress evolution during the heat treatment process and explores the effects of the solid-state phase transformation on stress. The residual stress, microhardness, and microstructural results are verified using X-ray residual stress analysis and microhardness measurements. During the heating stage of the quenching process, the cutter ring is heated slowly in a vacuum furnace. This slow heating rate leads to minimal differences between the center and surface regions, with low thermal strain values and small differences between different areas. Although the initial microstructure of the cutter ring (ferrite) fully transforms into austenite, the volume strain caused by the solid-state phase transformation (diffusive transformation) slightly increases the maximum and minimum values of the radial cross-sectional Mises stress and normal stresses in various directions. However, at this stage, the thermal stress caused by thermal strain dominates, and the impact of the solid-state phase transformation is relatively limited. During the cooling stage of the quenching process, the volume and transformation-induced plasticity (TRIP) strains caused by solid-state phase transformations significantly change the stress values. The TRIP strain in the near-surface region has the most significant impact on the stress results, which is mainly related to the dominance of the martensitic transformation (a non-diffusive transformation) in this region. Overall, during the heating stage of the quenching process, the thermal stress caused by the thermal strain remains the dominant factor, and the effect of the volume strain is limited. However, during the cooling stage, owing to the short cooling time and the resulting high cooling rate, the thermal stress increases rapidly and experiences the most dramatic changes during the heat treatment process. The solid-state phase transformation has a significant impact on the stress results during the heat treatment of the cutter ring. When the solid-state phase transformation is fully considered, the residual stress in the cutter ring can be accurately predicted. This provides a theoretical basis for the early prediction of failure behavior during the service life of the cutter ring. This study reveals that phase transformations during quenching, particularly martensitic transformations during cooling, play a crucial role in the overall stress distribution. The cutter ring surface is particularly affected, with high cooling rates leading to significant increases in thermal stress, which then transitions to residual stress. This understanding will contribute to improving the heat treatment process, reducing the likelihood of surface cracking, and extending the service life of the cutter ring. Additionally, the developed prediction model enhances the ability to predict potential failures and make necessary adjustments during the manufacturing and heat treatment stages to improve TBM performance in tunneling projects. In summary, this study highlights the critical role of heat treatment in determining the mechanical properties of TBM cutter rings. The accurate prediction and control of the residual stress, enabled by considering solid-state phase transformations, provide a solid theoretical foundation for improving the durability and reliability of these critical components during TBM operations.
  • Preparation and Properties of Fluorinated Acrylate Anti-pollution Flashover and Ultraviolet Aging Resistant Coatings
    YOU Yi, HE Cheng, WANG Xinxin, CHEN Zhuoyao, LIU Tong, HUANG Luyao, HAO Xiangping, ZHANG Dawei
    China Surface Engineering. 2026, 39(3): 365-378. https://doi.org/10.11933/CSE2026172
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    The loss of surface hydrophobicity significantly accelerates the degradation of room-temperature vulcanizing (RTV) coatings on electrical insulators, particularly under extreme environmental conditions. This progressive deterioration adversely affects the performance of the insulator, leading to a reduction in the flashover voltage, which is the critical threshold at which electrical breakdown occurs across the surface of the insulator. This reduction can considerably threaten the operational stability and safety of power systems because it increases the likelihood of electrical failures and system outages, thereby compromising the reliability of the entire electrical distribution network. In this study, these challenges were addressed by developing and evaluating advanced coatings designed to mitigate the adverse effects of environmental aging. A series of fluorinated methacrylate copolymers, designated GMX-X, were synthesized through a controlled chain polymerization reaction. This process was performed using a specific blend of methacrylate monomers, including glycidyl methacrylate, methyl methacrylate, and fluorinated methacrylate monomers, which were mixed in precise proportions and initiated using a polymerization initiator. Subsequently, fluorinated acrylate coatings (GMX-X/EOS) were prepared by incorporating the synthesized copolymers into epoxy siloxane and a cationic initiator at predetermined ratios. Structural characterization of these coatings was performed using Fourier transform infrared spectroscopy (FTIR), and their surface properties were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Hydrophobicity was evaluated using static contact angle measurements, with higher contact angles indicating superior water repellency. The ultraviolet (UV) aging resistance of the coatings was evaluated by analyzing the changes in the surface morphology, static contact angle, and gloss value. The antifouling performance of the coatings was investigated by examining alterations in the surface morphology and quantitatively assessed by measuring the non-soluble deposit density, which indicates the effectiveness of the coating in resisting the accumulation of contaminants. To further evaluate the effectiveness of the coatings, flashover voltage tests were conducted, and their antifouling flashover performance and UV aging resistance were measured. The results demonstrate that the fluorinated acrylate coatings, GMT-20/EOS and GMN-25/EOS, exhibited water contact angles of 99.08°and 91.49°, respectively, reflecting their strong hydrophobicity. The surface energies of these coatings were found to be 12.94 mN/m for GMT-20/EOS and 17.30 mN/m for GMN-25/EOS, indicating low surface energy and enhanced resistance to water absorption. The nonsoluble deposit densities for the GMT-20/EOS and GMN-25/EOS coatings were 0.154 and 0.179 mg/cm2, respectively. When these coatings were applied to insulators, the non-soluble deposit densities reached 0.012 and 0.020 mg/cm2, respectively, indicating very slight contamination, with the pollution level categorized as grade “a”. The flashover voltages for GMT-20/EOS- and GMN-25/EOS-coated insulators under mild contamination conditions were recorded as 27.6 kV and 30.3 kV, respectively, while the flashover voltages for GMT-20/EOS- and GMN-25/EOS-coated insulators under severe contamination conditions are recorded as 29.6 kV and 28.1 kV. After a seven-day period of UV irradiation, the flashover voltage of the heavily contaminated GMT-20/EOS-coated insulator was found to be 31.6 kV, which surpasses the flashover voltage of commercial RTV-coated insulators, recorded at 27.8 kV. These findings underscore the effectiveness of the fluorinated acrylate coating developed in this study. The coatings exhibit significant waterproofing and antifouling properties, effectively reducing surface contamination and water accumulation. In terms of aging resistance, these coatings exhibited notable UV resistance, which contributed to an extended service life. These coatings provide excellent waterproofing properties, antifouling performance, anti-pollution flashover capability, and UV aging resistance to insulation equipment. Consequently, these coatings are a highly promising solution for enhancing pollution flashover protection in electrical insulation systems, thereby improving the overall reliability and safety of the power distribution infrastructure.
  • Research on Cost-effectiveness Analysis Method of Equipment Remanufacturing Based on Simulation
    WANG Jia, CAI Zhihai, YAO Jukun
    China Surface Engineering. 2026, 39(3): 379-387. https://doi.org/10.11933/CSE2026173
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    Equipment remanufacturing is a sophisticated process that involves repairing or upgrading used equipment, particularly in the context of military applications, where retired and scrapped weapons can be restored to operational status. This practice is significant not only for maintaining the readiness of military forces but also for supporting national strategies for circular economy development, which emphasizes resource conservation and reduction of environmental impact.In the realm of equipment remanufacturing, especially within a market economy framework, the focus typically revolves around profit maximization under existing laws and regulations. However, for military equipment, the primary concern is often the restoration of combat capability. Therefore, a single cost analysis may not fully reflect the remanufacturability of equipment, and it becomes necessary to guide the remanufacturing process through a comprehensive cost-efficiency analysis. The serviceability of the equipment is a critical factor in evaluating the efficiency of the remanufacturing process. By analyzing the costs generated during the remanufacturing process and comparing them with the restored serviceability, a more accurate assessment can be made. The first step in this process is the construction of a detailed cost model for equipment remanufacturing. This model should take into account all the expenses involved, including labor, materials, and any additional resources required.Next, by collecting experimental data on remanufacturing process parameters and serviceability, a relationship model can be established using agent-based modeling techniques. This model helps in understanding how different process parameters affect the overall serviceability of the equipment. On this basis, a comprehensive cost-effectiveness model for equipment remanufacturing can be constructed. Simulation methods are then employed to solve the relevant models and carry out a detailed cost-effectiveness analysis. This approach allows for the accurate calculation of the cost-effectiveness ratio of equipment remanufacturing. By comparing and analyzing the cost-efficiency ratios of different remanufacturing process schemes, a solid basis for the selection of the most efficient remanufacturing scheme can be provided.Finally, an illustrative example is provided to validate the model and the method, demonstrating its applicability in real-world scenarios. This example serves to highlight the practicality and effectiveness of the proposed approach in guiding decision-making processes related to equipment remanufacturing.In summary, the remanufacturing of military equipment is a complex process that requires a detailed cost-efficiency analysis to ensure that the restored equipment meets operational requirements while adhering to budgetary constraints. By employing advanced modeling and simulation techniques, it is possible to make well-informed decisions that enhance the sustainability and effectiveness of military assets. This approach not only supports the national circular economy development strategy but also ensures that valuable resources are conserved and environmental pollution is minimized.
  • Effect of Stress Environment on the Microstructure of Local Dry Laser Cladding of S32101 Stainless Steel
    ZHAO Chenglu, ZHU Jialei, LI Guixin, LI Congwei, SU Yukun, ZHANG Guangliang
    China Surface Engineering. 2026, 39(3): 388-398. https://doi.org/10.11933/CSE2026174
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    During the operation of the plant, the corner area of the spent fuel pool is prone to corrosion, which causes the risk of leakage. Locally dry underwater laser welding provides an accurate solution to this in-service maintenance problem. To meet the needs of repairing the corner crack defects of the spent fuel tank, we have built a test platform that supports local dry underwater laser keracy test at atmospheric pressure and high pressure. We selected S32101 dual-phase stainless steel as the test material, and carried out the multi-channel process test of local dry underwater laser wire filling angle welding in air, underwater and simulated water depth of 20 m. The macroscopic cross-sectional morphology and microstructural characteristics of fillet welds were examined and compared across three distinct environments. The findings indicated that the fillet weld sections were free from defects such as porosity and inclusions, with a clear delineation of the fusion line between welds. The welds exhibited robust bonding with each other and with the base metal. Notably, the fillet welds produced in a high-pressure underwater environment were found to be thicker than those in a normal-pressure environment, while the weld leg dimensions were observed to be smaller. This was attributed to the slower cooling rate of the molten pool in an air environment, which allowed austenite sufficient time to grow, resulting in the finest grain size observed in the high-pressure underwater environment. Additionally, the degree of grain size nonuniformity was greater in the underwater environment compared to the air environment, where the largest grain size was recorded. Electron backscatter diffraction (EBSD) was employed to examine weld samples in both underwater and high-pressure underwater conditions using the Thermo Scientific Apreo 2C+EDAX Velocity Super. The analysis determined the composition, orientation, texture, and boundary characteristics of ferrite and austenite. The findings indicated that the austenite content was 45.3% in the underwater environment and 38.3% in the high-pressure underwater environment. This disparity is attributed to the fact that the phase equilibrium composition of ferrite relative to austenite is higher than that in the specified composition equilibrium state, a result of the rapid cooling of the weld metal. As the welding environment transitions from underwater to high-pressure underwater conditions, the grains exhibit a progressively more pronounced orientation. The disparity in grain size non-uniformity is more pronounced in high-pressure underwater settings compared to standard underwater conditions, resulting in a more pronounced preferred orientation. This phenomenon can be attributed to the enhanced cooling capacity of the water at depth, which alters the grain structure, increases the instability of the welding process, affects the distribution of the heat source, and consequently leads to a greater nonuniformity in grain size. The average Kam value for underwater laser welding is 0.58, while in a high-pressure underwater environment, it increases to 0.64. The austenite grain boundary exhibits a bimodal distribution characterized by low-angle boundaries (LABs) at 15 degrees and high-angle boundaries (HABs) at 50 degrees. Furthermore, the bimodal distribution trend of the austenite grain boundary becomes more pronounced in high-pressure underwater conditions.The multi-layer and multi pass fillet welds in three environments have good intergranular corrosion resistance. Through the test and analysis of open circuit potential, impedance spectrum and polarization curve, it is found that the corrosion resistance of fillet weld in different environments is air environment fillet weld>high pressure underwater environment fillet weld>underwater environment fillet weld>base metal. In conclusion, the simulation of multi-layer and multi-channel fillet welds within 20 m water depth can meet the repair needs of nuclear power projects, and the research results have laid a good foundation for the crack repair at the corner of the spent fuel pool in nuclear power plants.
  • Effects of Pulse Frequency on the Corrosion and Wear Resistance of Anodic Oxidation Films on 6xxx Series Aluminum Alloys
    XIA Dingwei, GUAN Lei, LI Yu
    China Surface Engineering. 2026, 39(3): 399-410. https://doi.org/10.11933/CSE2026184
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    The 6xxx series of aluminum alloys is extensively utilized in marine vessels and architectural profiles, with corrosion resistance and wear resistance being key indicators of its quality. In this study, electrochemical tests were conducted to study the corrosion resistance of the pulse-anodized films on 6xxx series aluminum alloys, while reciprocating friction and wear tests were used to investigate the ware resistance of the film. Scanning electron microscopy was used to observe and analyze the surface and cross-sectional microstructural characteristics of the films. The results showed that as the pulse frequency increased, the self-corrosion current density of the oxide film in NaCl solution first decreased and then increased, while the open-circuit electrochemical impedance first increased and then decreased. At a pulse frequency of 1 000 Hz, the corrosion rate was 1 to 2 orders of magnitude lower than at other pulse frequencies. Friction and wear tests indicated that as the pulse frequency increased, the initial friction factor and the time for its significant reduction first increased and then decreased. At a pulse frequency of 1 000 Hz, the initial friction factor was the smallest, and the time required to wear through to the substrate was the longest. Microscopic analysis revealed that the pulse-anodized oxide film at 1 000 Hz had the lowest porosity, the best pore size uniformity, the lowest proportion of large pores, and the thickest film, resulting in the best corrosion and wear resistance. Correlation analysis showed that porosity, pore size uniformity, and the proportion of large pores are the main factors affecting the corrosion resistance of the pulse-anodized oxide film, while film thickness is the key factor influencing its wear resistance. To evaluate the performance of pulse-anodized films, a multi-faceted experimental approach was adopted. First, electrochemical tests were conducted in a 3.5wt.% NaCl solution (simulating marine conditions) using a three-electrode cell with a saturated calomel reference electrode (SCE) and a platinum counter electrode. Potentiodynamic polarization curves were recorded at a scan rate of 1 mV/s to determine the self-corrosion current density (icorr), a direct indicator of corrosion rate. Electrochemical impedance spectroscopy (EIS) was performed at open-circuit potential over a frequency range of 105 to 10-2 Hz to assess the charge transfer resistance and capacitive behavior of the oxide films. For wear resistance evaluation, reciprocating ball-on-flat friction tests were conducted under a 5 N normal load using a 5 mm silicon nitride ball as the counterface. The initial friction factor and the time required for the friction factor to stabilize (indicating film breakdown) were recorded. Microstructural characterization involved scanning electron microscopy (SEM) of both surface and cross-sectional samples. Surface porosity and pore size distribution were quantified using image analysis software, while film thickness was measured at five locations per sample to ensure statistical validity. The enhanced corrosion resistance at 1 000 Hz arises from three synergistic factors: ① Reduced porosity limits chloride ion diffusion pathways; ② Narrow pore size distribution minimizes localized current density variations during corrosion; ③ Fewer large pores act as stress concentrators. For wear resistance, film thickness governs load-bearing capacity—thicker films distribute shear stresses more effectively, delaying plastic deformation of the aluminum substrate. These findings provide actionable guidelines for marine component manufacturers. Implementing 1 000 Hz pulse anodization could extend the service life of ship hulls and offshore platform components by 3-5 times in corrosive environments. Architectural applications would benefit from reduced maintenance costs for coastal structures. This comprehensive study establishes pulse frequency as a critical control parameter for optimizing anodized films on 6xxx aluminum alloys. The 1 000 Hz process achieves an optimal balance between ionic migration dynamics and oxide growth kinetics, producing films with superior barrier properties and mechanical resilience. The demonstrated correlation between process parameters, microstructure, and performance provides a scientific foundation for next-generation surface engineering strategies in the marine and construction industries.
  • Effect of Laser Shock Peening Process without Coating Parameters on Mechanical Properties and Surface Integrity of AISI 9310 Gear Steel
    YANG Fei, ZHOU Liucheng, PAN Xinlei, WANG Chenxi, LIU Ping, SUN Xin
    China Surface Engineering. 2026, 39(3): 411-421. https://doi.org/10.11933/CSE2026175
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    Gears constitute the core components of helicopter reducers, and the failure of heavy-load transmission gears directly impacts the reliable operation of the reducer, potentially endangering the service safety of the helicopter. Enhancing the service performance and reliable working margin of gears through surface post-treatment technologies holds significant military and economic value. Laser shock peening, as an advanced surface strengthening technique, aims to achieve efficient surface modification of metallic materials. However, its application to geometrically complex parts presents technical challenges. Therefore, an attempt is made to modify the surface of gears using laser shock peening without coatings. To verify the efficacy of laser shock peening without coatings in improving the properties of gear steel, strengthening experiments are conducted with varying process parameters. The experiment innovatively employs a smaller spot size and lower energy level for processing. Specimens of specific material grades undergo grinding, vacuum carburizing, and heat treatment to simulate the transmission gears of a reducer, providing a process reference for real gear components. AISI 9310 steel, a typical martensitic steel, is selected for study. The sample exhibits a complete carburized layer of approximately 420 μm, with a stable hardness of 625 HV within this range. Beyond 1 000 μm, where the matrix is entirely outside the carburizing zone, the hardness stabilizes at 430 HV. The laser beam interacts directly with the specimen in an atmospheric environment. Given the unique structure of gear parts, a water-optical coaxial strengthening method is adopted. During the optimization of the laser process, laser energy is first optimized, followed by the number of laser shocks. The effects of laser parameters on mechanical properties and surface morphology are systematically analyzed. The samples are characterized using an optical microscope, microhardness tester, residual stress meter, roughness meter, and atomic force microscope. The results indicate that laser shock peening without coatings introduces a maximum work-hardened layer of 530 μm and a residual compressive stress layer of 450 μm in the depth direction of the sample. The substantial improvement in subsurface mechanical properties is attributed to the plastic deformation induced by the plasma shock wave in the gradient direction. After strengthening, the maximum hardness reaches 689.9 HV, and the residual compressive stress increases to 738.9 MPa. The direct irradiation of the laser beam on the sample surface leads to heat accumulation, causing a rapid increase in surface roughness to a maximum of 1.509 μm. This results in the formation of a periodic micro-convex structure with a regular arrangement. As laser energy and the number of shocks increase, this structure gradually evolves into a regular rectangular pattern, exhibiting self-lubrication properties. An effective work-hardening layer is formed along the depth direction of the specimen after strengthening. An increase in laser energy or frequency significantly enhances the work-hardening effect of laser shock peening without coatings. Additionally, a high-amplitude residual compressive stress is introduced into the specimen along the depth direction, forming a residual compressive stress layer with the same thickness as the hardened layer. The results of process optimization reveal that a surface treated with 120 mJ per strengthening cycle, applied twice, forms a periodic rectangular microstructure pattern, resulting in the most significant improvement in comprehensive mechanical properties. The influence of laser shock peening without coatings process parameters on the properties of AISI 9310 steel is studied, and the process parameters are further optimized. The effectiveness of laser shock peening without coatings in improving the mechanical properties of gear steel materials is verified, providing data accumulation and technical support for the subsequent enhancement of friction performance, rolling contact fatigue performance, and bending fatigue performance of gears.
  • Investigation of Lubrication Wear and Corrosion Resistance of BTSA/PTFE/EPN Coatings
    MA Qiwei, WAN Binghua, CHEN Mingkai, HUANG Jinhu, LIU Jingying, MA Yanjun, CHEN Lei, ZHANG Dingjun, CHEN Jianmin
    China Surface Engineering. 2026, 39(3): 422-435. https://doi.org/10.11933/CSE2026063
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    In complex marine environments, the critical moving components of high-tech marine engineering equipment are inevitably subjected to both wear and corrosion, which significantly reduce their operational lifespan. Currently, research efforts both domestically and internationally tend to focus primarily on enhancing the individual properties of materials, with limited comprehensive consideration for the simultaneous improvement of antifriction, wear resistance, and corrosion resistance. This often results in mutual constraints among these properties, making it challenging to achieve a balanced performance. Consequently, the development of novel lubricating and anticorrosive materials and technologies is essential to ensure the high reliability and longevity of marine equipment. The objective of this study is to address these challenges by designing and fabricating an integrated coating that combines superior corrosion resistance and tribological performance. This is achieved through the utilization of 2-benzothiazole succinic acid (BTSA), an environmentally friendly organic corrosion inhibitor known for its excellent anticorrosive properties, and polytetrafluoroethylene (PTFE), a solid lubricant with low surface energy. The study explores the impact of BTSA on the lubrication, wear resistance, and anticorrosion properties of the composite coating while also elucidating the underlying mechanisms driving these enhancements. The methodology involves the systematic evaluation of the BTSA-PTFE composite coating’s performance in simulated marine environments. The coating undergoes rigorous testing under both dry and corrosive conditions to assess its tribological and anticorrosive properties comprehensively. Specifically, the BTSA content is varied to determine the optimal concentration for enhancing the coating’s overall performance. Experimental results indicate that incorporating BTSA at an 8% concentration significantly improves the coating’s properties. Under dry friction conditions, the composite coating’s friction coefficient is reduced by 75.22% compared to the original coating, and its wear resistance is enhanced by a factor of 3.3. In corrosive media, the friction coefficient is reduced to 0.046. Electrochemical corrosion performance tests conducted over 30 d, along with 210-day salt spray corrosion tests, demonstrate that the composite coating exhibits exceptional anticorrosion performance. The improvements are attributed to the synergistic effect of BTSA and PTFE, which modifies the surface characteristics of the coating, forming a barrier structure and a corrosion-inhibiting passivation film. The investigation into the underlying mechanisms reveals that the combination of BTSA and PTFE creates a synergistic effect that significantly alters the surface characteristics of the coating. BTSA contributes to the formation of a passivation film that serves as a protective barrier against corrosive elements, effectively inhibiting electrochemical reactions that typically lead to corrosion. This enhances the coating’s ability to resist corrosion over extended periods, even in harsh marine environments. Furthermore, the low surface energy of PTFE plays a crucial role in enhancing the lubricating properties of the coating. The solid lubricant forms a smooth, low-friction surface that minimizes direct contact between moving parts, thereby reducing wear and extending the lifespan of the components. This dual enhancement of lubrication and corrosion resistance obtained through the synergistic interaction of BTSA and PTFE presents a significant advancement in the development of protective coatings for marine applications. The study introduces a novel approach to developing chromate-free anticorrosive lubricating protective coatings, addressing the critical issue of wear and corrosion in marine environments. By integrating BTSA and PTFE, the research demonstrates a significant step forward in material design, offering a robust foundation for the further exploration and optimization of composite coatings. The findings underscore the potential of this synergistic combination in enhancing the durability and effectiveness of protective coatings, providing valuable insights for the development of high-performance coatings with integrated properties. In conclusion, this research not only enriches the theoretical understanding of anticorrosive coating materials but also offers practical solutions for the development of advanced materials capable of withstanding the rigors of marine applications. The BTSA-PTFE composite coating represents a promising advancement in ensuring the reliability and longevity of marine engineering equipment, paving the way for innovative approaches in material science and engineering. By addressing the complex interplay between wear and corrosion, this study contributes to the broader goal of enhancing the performance and sustainability of marine infrastructure, highlighting the importance of interdisciplinary research in tackling complex engineering challenges.
  • Effect of Laser Surface Texturing Process on Microstructure Formation Quality of Gear Steel
    ZHANG Qiang, LIU Yuhang, LU Xing, XU Xiangbang, LIU Fuyun, TAN Caiwang
    China Surface Engineering. 2026, 39(3): 436-447. https://doi.org/10.11933/CSE2026067
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    Existing research on microtextures predominantly concentrates on their wear-reducing effects on working surfaces and the associated influencing factors. However, comprehensively understanding of microtexture wear-reduction mechanisms remains elusive. Moreover, the effects of heat input and arrangement spacing on the formation quality of microtextures remains relatively shallow. This knowledge gaps hinder effective implementation of microtextures for wear reduction in practical applications, highlighting the need for further research. This study addresses the issue of excessive wear in the side-by-side gear assemblies of vehicle power systems. A novel wear-reduction strategy was developed that involves the use of laser technology to create microtextures on the end faces of a 38CrSi gear steel to enhance the load-carrying capacity of the lubricating oil, and thus mitigate gear wear. Initially, a mathematical lubrication model was constructed based on the Reynolds equation. This model analyzes the influence of the microtexture arrangement spacing on the pressure distribution of the lubricating oil film. Through meticulous calculations of the oil-film pressure distribution under various arrangement spacings, a significant finding emerged: reducing the microtexture arrangement spacing can effectively improve the load-carrying capacity of the oil film. Specifically, when designing wide-spaced microtextures, the optimal spacing should be below 0.30 mm, and for narrow-spaced ones, it should not exceed 0.15 mm. This discovery provides crucial theoretical guidance for optimizing the layout of microtextures. Subsequently, a series of process experiments were conducted by varying the microtexture arrangement spacing and scanning speed. The experimental results revealed that when the arrangement spacing was narrow, a large heat input caused mutual thermal interference owing to the overlap of the heat-affected zones. This interference disrupts the stability of the microtexture-forming process and prevents the formation of high-quality microtextures. However, a small heat input fails to meet the requirements for the depth and size of the microtextures, which are essential for their proper functioning. Laser scanning speed is crucial in microtexture preparation. A lower scanning speed led to significant remelting and backfilling of the metal deposition layer. This phenomenon affects the depth and shape of the microtextures, resulting in an irregular and less effective structure. Conversely, a higher scanning speed may cause insufficient heat input, leading to poor forming quality, such as incomplete microtexture formation or weak bonding with the substrate. Finally, an optimized microtexture preparation process is proposed. After thorough experimentation and analysis, the optimal laser texturing process parameters were determined. These parameters included a laser power of 160 W, a scanning speed of 10 mm/s, a pulse frequency of 95 kHz, 10 processing cycles, and an arrangement spacing of 0.3 mm. This optimized process effectively enhanced the lubrication performance of the surface of the gear steel, significantly reducing wear. It also demonstrates good adaptability in industrial applications and offers a practical solution for improving the durability of mechanical components. Additionally, this study provides a valuable reference for preparing microtextures on similar metal surfaces. This promotes the broader application and development of microtexture technology in diverse industries such as machinery manufacturing, where reducing friction and wear is crucial for improving the efficiency and lifespan of equipment, and aerospace, where component reliability under extreme conditions is crucial.
  • Influences of Friction Pair Characteristics on Tribological Properties of Carbon-based Coated Self-lubricating Radial Spherical Plain Bearing
    LI Zhen, CHEN Qihan, CHEN Yongjin, ZHANG Zhinan
    China Surface Engineering. 2026, 39(3): 448-456. https://doi.org/10.11933/CSE2026185
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    Coated self-lubricating radial spherical plain bearings (SSPBs) are widely used under extreme working conditions owing to their self-alignment, load resistance, and wear resistance, among other performance advantages. Ensuring the operation of the equipment in a self-lubricating radial spherical plain bearing wear life is of great significance. Several reports have been published regarding the tribological properties of self-lubricating coatings. However, little attention has been given to the influences of the friction pair characteristics of coated self-lubricating radial spherical plain bearings on their tribological properties. Two types of self-lubricating radial spherical plain bearings with hydrogen-containing diamond-like coatings were prepared via unbalanced magnetron sputtering: coated on the outer spherical, non-coated on the inner spherical, coated on the inner spherical, and non-coated on the outer spherical. The microstructure, phase composition, tribological properties, and failure mechanism of self-lubricating plain radial spherical bearings were investigated using scanning electron microscopy, energy dispersive spectrometry (EDS), Raman spectroscopy, and a self-lubricating plain radial spherical bearing testing machine in a vacuum environment. The test results showed that the self-lubricating coating combined well with the outer spherical of the inner ring and the inner spherical of the outer ring. There were no microdefects, such as cracks or pores. Based on the microscopic morphology of the coating cross-section, the coating thicknesses of the inner spherical of the outer ring and the outer spherical of the inner ring were approximately 2.04 μm and 3.66 μm, respectively, under the same preparation parameters. The ID/IG values before and after the test were compared. The ID/IG value of the hydrogen-containing diamond-like coating increased after vacuum testing. These numerical changes indicated that the self-lubricating coating underwent a graphitization transition. The friction torque of the two types of self-lubricating radial spherical plain bearings initially fluctuated sharply, changed smoothly, and finally changed dramatically under vacuum swing test conditions. The average frictional torque values of the bearing coated on the inner and outer spherical were 0.005 and 0.008 N·m, respectively. In addition, the change law of the friction temperature with time rose rapidly at the beginning, then rose steadily, and finally rose sharply. Therefore, according to the change law of the friction torque and friction temperature increases with time, the service stages of the two types of SSPBs can be divided into running-in, stable, and failure periods. The life of a plain self-lubricating radial spherical bearing coated with an inner ring (21 230 times) was longer than that of the plain self-lubricating radial spherical bearing coated with an outer ring (18 590 times) under the influence of the thickness and surface roughness of the self-lubricating coating. The results of the friction and wear tests showed that to improve the tribological properties and wear life of the coated self-lubricating radial spherical plain bearings, it is necessary to increase the thickness of the self-lubricating coating and reduce the roughness of the relatively moving surface. According to the microscopic wear morphologies of the inner and outer rings of the two types of self-lubricating radial spherical plain bearings, there is a large furrow morphology along the relative movement direction. These results indicate that the wear failure mechanism of the bearing was abrasive wear in a vacuum environment. In addition, black areas were observed on non-coated surfaces. The results of an EDS analysis showed that the black region contained a large amount of carbon, indicating that material transfer occurred during the relative movement of the inner and outer rings. Metal-to-metal grinding occurs when the self-lubricating coating is worn. In a vacuum environment, the adhesion of metal pairs occurs easily. Therefore, adhesive wear failure occurred during the later wear period of the self-lubricating plain radial spherical bearings. These research findings can guide the design and preparation of self-lubricating coatings for coated self-lubricating spherical plain bearings, enhance the service lives of bearings under harsh operating conditions, and leverage their performance advantages.
  • Oxidation and Failure Behavior of Cr Coating on Zr-alloy Cladding Tubes Fabricated via Extreme High-speed Laser Cladding
    CAI Shiyang, DU Pengcheng, YU Siliang, PANG Xuming, PU Jibin
    China Surface Engineering. 2026, 39(3): 457-467. https://doi.org/10.11933/CSE2026186
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    Since the nuclear leakage accident in Fukushima in 2011, accident-tolerant fuel (ATF) garnered significant attention. The development of coatings on existing Zr alloys to maintain the original design and structure of fuel assemblies has become a key research topic. Cr is widely used in Zr-alloy cladding coatings owing to its excellent corrosion and high-temperature steam oxidation resistance. Extreme high-speed laser cladding (EHLA) effectively addresses issues such as reduced corrosion resistance due to columnar coatings shown in other preparation techniques, inadequate adhesion between the coating and substrate, and excessive stress causing substrate deformation or cracking, thus demonstrating significant application prospects in surface modification. Therefore, investigating the preparation process, coating structure, corrosion resistance, and corrosion mechanism of EHLA Cr coatings is crucial for improving the performance of ATFs. In this study, Cr coatings are prepared on Zr alloy tubes using EHLA technology, and isothermal steam oxidation experiments are conducted at temperatures ranging from 900 to 1 300 ℃. The microstructural changes and oxidation kinetics are systematically analyzed. Isothermal steam oxidation experiments are performed in a tube furnace equipped with a steam generator. Before the experiments, Zr-alloy tubes and Cr-coated Zr alloy tube samples are cut into 1-cm-long semicircular segments and placed on alumina rods in crucibles to prevent oxidation on the inner surfaces. After evacuating the air from the tube furnace, argon gas at atmospheric pressure is introduced, followed by heating to 1 200 ℃ at a rate of 5 ℃/min. Steam is introduced through the steam generator for oxidation durations of 10, 30, 45, 60, 120, 180, and 240 min, followed by natural cooling to room temperature inside the furnace. Throughout the oxidation process, steam is introduced at a flow rate of 200 mL/min and a concentration of 50% via argon gas. An analytical balance (accuracy=0.01 mg) is used to measure the weight changes of the crucible and samples before and after oxidation. Cross-sectional characterization of the samples involve embedding in epoxy resin, grinding, polishing, and ultrasonic cleaning, followed by analysis using scanning electron microscopy and energy-dispersive spectroscopy. A ring compression test is performed using a 30 kN universal material testing machine. The hardness of the samples is measured using a Vickers hardness tester with a test load of 0.1 kg and a load time of 10 s. The samples are embedded in epoxy resin for fixation, thereby exposing the upper section for hardness testing. Research shows that Cr coatings deposited via EHLA exhibit a metallurgically dense structure, thus significantly improving the microhardness and ring compression performance of Zr-alloy pipes and decelerating the oxidation of the Zr matrix in high-temperature steam environments. At 1 200 ℃ in a steam oxidation environment, the laser-clad Cr coating provides at least 120 min of effective protection for the Zr-alloy substrate, with an oxidation weight gain of only 43.5% compared with that of uncoated Zr alloy samples. After 120 min of oxidation, accelerated coating failure occurred owing to increased oxidation and elemental interdiffusion, thus resulting in cracks and pores on the surface and internally; consequently, protection for the Zr alloy is nullified after 240 min. Meanwhile, the clad samples exhibit good stability within the temperature range of 900-1 300 ℃, although their oxidation resistance decrease with increasing temperature. The experimental analysis and kinetics cumulatively show that the power-law oxidation model can accurately predict the oxidation behavior of Cr coatings in high-temperature steam environments to some extent, thus providing an important reference for assessing the oxidation extent of other coatings. Therefore, high-speed laser-clad Cr coatings offer effective protection for ATF cladding materials under extreme conditions. By analyzing the oxidation and failure behaviors of laser-cladding Cr coatings in high-temperature steam environments, the corrosion process and failure mechanism in extreme environments can be investigated comprehensively, thus providing new ideas for solving the oxidation problem of Zr alloy cladding in extreme environments.
  • Effects of Process Parameters on the Properties of Cold-sprayed WC-17Co/Ni Composite Coatings
    LI Wen, LI Zhiyong, SONG Chao, WANG Cong, WANG Mingyuan, LUO Xiaotao, LI Wenya
    China Surface Engineering. 2026, 39(3): 468-479. https://doi.org/10.11933/CSE2026187
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    Aluminum alloys are widely used in aerospace applications such as aircraft structures, engine components, and cabin walls owing to their excellent specific strength, superior machinability, and light weight. However, they still face certain challenges, including wear resistance, corrosion resistance, and durability, in practical applications. To enhance the properties of aluminum alloys, WC-17Co hard-alloy coatings have been applied for surface protection. Cold spraying, as an advanced solid-phase deposition technology, has the advantage of significantly reducing the working temperature compared with traditional thermal spraying. This low temperature enables cold spraying to effectively avoid metal oxidation and harmful interfaces at high temperatures, ensuring that the microstructure and properties of the spraying material are not degraded, extending the service life, and improving the material’s durability. Accordingly, WC-17Co/Ni composite coatings with a volume fraction of 80vol.% WC-17Co were prepared on AA2024 substrate via cold spraying. The microstructure, mechanical properties, and bending properties of the AA2024 substrate were analyzed via optical microscopy, scanning electron microscopy, microhardness testing, and a universal material testing machine. The effects of gas pressure, gas temperature, and standoff distance on the deposition efficiency, microstructure, mechanical properties, and bending properties of the cold-sprayed 80vol.% WC-17Co/Ni composite coating were investigated via a three-factor, three-level orthogonal test design. The results showed that gas pressure had the greatest effect on the coating thickness, hard-phase content, and porosity, followed by gas temperature; the standoff distance had no significant effect. Higher gas pressures and temperatures can increase the particle velocity and improve the coating deposition quality. When the spraying process parameters are high (4, 5 MPa; 650, 750 ℃), the 80vol.% WC-17Co/Ni composite coating exhibits a relatively dense structure (the porosity decreases to ~1%) and high deposition efficiency (the coating thickness exceeds 300 μm), and the WC-17Co volume fraction in the coating exceeds 60vol.%. Additionally, the composite coating exhibited excellent mechanical properties. The bonding strength was slightly affected by the spraying parameters; all coatings exhibited good bonding ability (the bonding strength exceeded 30 MPa), and the coating microhardness was the most sensitive to gas pressure changes. Higher gas pressures enhanced the work-hardening effect of the composite coating by increasing the particle velocity and effectively increasing its microhardness. When the gas pressure reached 5 MPa, the average coating microhardness exceeded 400 HV0.3. Furthermore, to further evaluate the influence of changes in the cold-spraying process parameters on composite coating durability, the WC-17Co/Ni composite coatings were tested at 90°three-point bending. The bending performance of the cold-sprayed 80vol.% WC-Co/Ni composite coating under different process parameters did not differed significantly. Although cracks appeared in the bent part of the coating, no spalling phenomenon was observed in the coating, which was caused by the WC-Co and Ni particles deeply embedded in the substrate. The WC-Co/Ni composite coating exhibits good adhesion to the AA2024 substrate. Based on experimental results, the optimal process parameters were identified as follows: gas pressure: 5 MPa; gas temperature: 750 ℃; and standoff distance: 20 mm, ensuring high-performance 80vol.% WC-17Co/Ni composite coatings. These findings provide crucial experimental data and a theoretical framework for designing superior surface coatings tailored to aerospace aluminum alloys. Overall, this study provides valuable insights into the influence of cold-spraying process parameters on the microstructure and properties of WC-17Co/Ni composite coatings. This highlights the efficacy of cold spraying in enhancing the surface protection of aerospace aluminum alloy components and promising advancements in materials engineering and application practices within the aerospace industry.
ISSN 1007-9289　CN 11-3905/TG
Supervised by: China Association for Science and Technology
Sponsored by: Chinese Mechanical Engineering Society
Edited and Published by: Editorial Office of China Surface Engineering
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