Macroscopic solid superlubricity (with a friction factor on the order of 0.001) in diamond-like carbon (DLC) films has attracted widespread attention in the academic community in recent years due to its significant potential in the domain of solid lubrication under extreme working conditions, such as vacuum, high contact pressures, and wide temperature ranges. However, the deposition methods and bonding structures of DLC films are diverse, and specific intrinsic compositions and structures, as well as external working conditions, are required to achieve macroscopic superlubricity in DLC films. Thus, this review discusses current research progress on the structural regulation of DLC films, diverse superlubricity behaviors in DLC films, key influencing factors, and their corresponding mechanisms. First, the current structural classification, deposition methods, and recent research on the bonding structure regulation principles of DLC films for solid superlubricity were summarized. An effective strategy for synthesizing DLC films with superior solid superlubricity is to adjust the composition and energy of deposition ions to balance the surface chemisorption and subsurface implantation growth modes, leading to an optimized combination of mechanical stiffness and hydrogen content of DLC films. Subsequently, the research trajectory on superlubricity in DLC films was reviewed, and the latest developments categorized by mechanisms were introduced. The combinations of DLC and environmental media available for superlubricity are diverse, and include hydrogenated amorphous carbon (a-C:H) in dry inert atmospheres, doped a-C:H in humid air or water-based liquids, hydrogen-free DLC in oil-based liquids, and DLC films in nanomaterial-containing environments. Furthermore, the influencing mechanisms of the internal elemental composition and bonding structure of DLC films, as well as external working conditions such as the environment, contact pressure, and temperature on the superlubricity behavior of DLC are discussed in detail. Sufficient hydrogen content is necessary for DLC films to achieve superlubricity in dry inert atmospheres, such as N₂, Ar, and vacuum. The self-lubrication properties of DLC films can be significantly affected by O₂ and H₂O molecules in humid air, due to intensified interfacial chemical bonding, disordered water adsorption layers, enhanced hydrogen bonding forces, and van der Waals forces caused by tribo-chemically generated highly polar groups. Elemental doping with Si, S, and Ti can effectively suppress the moisture sensitivity of DLC films via their participation in the structural evolution of sliding interfaces. Sufficiently high contact pressure is also necessary for solid superlubricity in DLC films, which is mainly due to the self-lubrication effect of contact-pressure-triggered locally short-range-ordered layered-like sp² nanoclustering structures. Overly high contact pressure deteriorates the superlubricity state of DLC films through hydrogen detachment and microstructural destruction of the counterpart surfaces. Ultralow temperature (<-100 ℃) can increase the friction factor of DLC films due to the suppression of thermal activation and structural evolution of sliding interfaces. On the contrary, high temperature (>300 ℃) facilitates the failure of a-C:H films due to excessively promoted hydrogen detachment, graphitization, and oxidation in air. Additionally, the mechanism behind the solid superlubricity of DLC is discussed from the perspective of interfacial bonding structural evolution. The tribo-generated transfer films on smooth-stiff surfaces, hydrogen passivation of surface dangling bonds, and generation of short-range ordered graphite-like nanostructures are key factors for the establishment of superlubricity in DLC films, which simultaneously suppress the three main contributors of macroscopic friction force: interfacial abrasion, shearing, and adhesion effect. Finally, the unresolved issues and related research trends in the underlying science and engineering applications of DLC are summarized. The connection of deposition parameters with growth theories, the nanostructure of superlubricious sliding surfaces and their evolutionary pathway, the environment and working condition sensitivity, and the influencing mechanisms of multi-element, multilayer, micro-nano textured, and media-synergistic lubrication strategies require further research. These findings can provide technical support for the design and application of superlubricious DLC films for dry-sliding friction pairs under extreme engineering conditions.

In the current era of industrial manufacturing and materials science, continuously enhancing material properties to meet the growing application challenges is an ongoing task. Metal materials play a key role in many industries because of their excellent mechanical properties and wide range of applications. Nevertheless, these metals are often subjected to wear, corrosion, and fatigue damage during practical use, which severely reduces their service life and reliability. Therefore, studying effective surface modification technologies that can improve the surface integrity and properties of metals has become a core issue in materials science research. Ultrasonic surface rolling processing (USRP) is an advanced material surface modification technology that combines ultrasonic energy and high-frequency mechanical vibrations to nano-strengthen the metal surface. This technology can cause plastic deformation on the surface of the material and significantly improve its surface integrity and mechanical properties. USRP can generate residual compressive stress on the surface of a material, effectively preventing the formation and expansion of cracks and reducing the permeability of the corrosive medium. In addition, this technology can form a nanostructured layer with a gradient grain size and orientation, thereby significantly enhancing the surface hardness and wear resistance of the material. This review summarizes the research progress in USRP in the fields of steel, aluminum alloy, titanium alloy, magnesium alloy, nickel alloy, and high-entropy alloy. It is demonstrated that these materials have achieved remarkable results in surface nano-strengthening and microstructural and performance improvement following USRP treatment. USRP technology can not only refine the grain size, reduce the surface roughness, and improve the surface hardness, but also convert the residual tensile stress into residual compressive stress to obtain a deeper nano-gradient hardened layer and residual compressive stress-affected area. This compensates for the low production efficiency of traditional mechanical processing methods as well as the mismatch between the working environment and performance requirements of high-performance materials. Finally, future application prospects and development directions of USRP are discussed. It is expected that focus will be placed on the refinement of theoretical models and the diversification of working methods. This research will further explore the theory of contact mechanics and surface integrity to develop a prediction model that can optimize the process parameters. In addition, USRP technology will be adapted to deal with complex parts and improve the efficiency and performance through multi-field coupling and process integration. The expansion of the application range will include composite materials and high-tech fields, including deep-sea exploration and aerospace satellites.

The advancement of technology in today’s society has led to higher performance demands for machining tools, and tool coatings have become a primary method for enhancing tool performance. To fully exploit the inherent properties of coated tools, post-treatment is essential. This paper aims to summarize the commonly used post-treatment methods for coated tools, which include sandblasting, polishing, heat treatment, energy field / beam treatments, and others. Sandblasting is the most widely used post-treatment method for coatings. The effectiveness of the post-blasting treatment is determined by three key parameters: grit, pressure, and time. Careful analysis of these variables shows that sandblasting can efficiently remove larger particles from the coated surface while enhancing its overall quality, provided that appropriate conditions are met. Another traditional surface-polishing technique is mechanical polishing, which uses flexible polishing tools, abrasive particles, and other media to modify the workpiece surface. This process effectively removes burrs and larger particles, resulting in a significant reduction in surface roughness. Both sandblasting and mechanical polishing contribute to achieving finer surface finishes on coated materials. Heat treatment is another widely adopted method for both tool treatment and post-treatment of coated tools. During the deposition of tool coatings, the substrate temperature remains low, causing rapid cooling of the coating material. Due to differences in the thermal expansion coefficients between the grains within the coating, thermal stress arises, which can accelerate tool failure. Heat treatment plays a crucial role in relieving some of the strain energy within the coating, adjusting the state of the coating-substrate interface, enhancing microstructural properties, and ultimately improving the performance of coated tools. A recent advancement in post-treatment methods for coatings is the use of energy fields or beam treatments. Energy field treatments include various techniques such as magnetic fields, electron beams, ion beams, lasers, and other similar methods. Compared to mechanical and heat treatments, energy field treatments offer greater controllability and a broader range of action. Research indicates that applying different energy field parameters during post-treatment can enhance not only the surface integrity of the coating but also the bonding strength between the coating and the underlying substrate. This technique involves localized heating of specific areas on the coating using high-density energy, leading to surface remelting and changes in roughness. Additionally, rapid heating and the ensuing energy waves generate thermal stress, which strengthens the coating, substrate, and bonding interfaces. As a result, this process significantly enhances the bonding strength between the coating and the substrate, thereby improving the overall performance of the coating.Although progress has been made in the post-treatment of coated tools, these methods are not yet widely applied in practice, with the exception of polishing. By analyzing the advantages and disadvantages of each post-treatment method, this study clarifies their respective scopes of application, addresses the fragmentation of research in this field, improves understanding of post-treatment methods for tool coatings, and provides a useful reference for the future development of post-treatment technology for coated tools.

采用低压等离子喷涂技术在镍基单晶高温合金上制备了NiCoCrAlYTa涂层,研究了不同功率参数制备的涂层在900℃175 h氧化后的特性,探讨了该涂层的氧化和退化机理.结果表明,3种功率制备的涂层都达到完全抗氧化级水平,其平均氧化速率分别为0.01 g/m2·h、0.01g/m2·h和0.0026g/m2·h,但不同涂层的氧化行为有所不同.3种试样氧化后表面形成了大量的β-Al2O3,并在涂层表面发生选择性氧化.X衍射分析表明,涂层发生了退化.

Laser cladding technology is widely used in the field of surface protection and remanufacturing because of its advantages, such as metallurgical bonding between the cladding layer and substrate, high processing efficiency, low dilution rate, and high energy input. It improves the wear resistance and corrosion resistance of the substrate, as well as the life of the cladding layer of the parts. However, instantaneous melting and rapid solidification of the melt pool during the laser cladding process lead to uneven stress within the cladding layer. It has been shown that even if the basic parameters are the same, the scanning paths and scanning time intervals of different lasers significantly influence the temperature distribution, and an uneven temperature distribution further leads to an uneven distribution of thermal stresses, which can cause coating quality issues. To analyze the effect of the scanning paths on the residual stress and tribological properties of the multi-pass laser cladding layer, a multi-pass laser cladding layer of Inconel 718 was prepared on 316L stainless steel using different scanning paths, and the distribution of residual stress in the cladding layer was investigated based on the thermoelastic-plastic model and the residual stress analyzer. The microstructure and hardness distribution of the cladding layer were studied using an X-ray diffractometer, a metallurgical microscope, and a hardness testing system. The tribological properties of the cladding were evaluated using a comprehensive material surface property tester and a laser confocal microscope. The results show that, owing to the difference in temperature cycling during the cladding process, the reciprocating scanning path has the shortest interval between each cladding pass and the lowest surface residual stress. The isotropic and dispersive scanning paths exhibit intermediate surface residual stress levels, while the shrinkage scanning path, which has the largest accumulation of heat in the central region of the cladding layer, exhibits the highest surface residual stress. The isotropic scanning path results in the most homogeneous microstructure due to the differences in temperature cycling during the process. In terms of microstructure, the isotropic scanning path exhibits the most uniform microstructure. Due to the consistent time intervals between each fusion cladding pass, the cooling process remains stable, resulting in minimal changes in crystal size from the cladding layer to the fusion zone. The shrinkage path has the largest accumulation of heat in the fusion cladding layer, and the low cooling rate allowed the crystals more time to grow, which resulted in significant changes in the size of the crystals at the bottom. Owing to the differences between the primary arm spacing and the volume fraction of the Laves phase in the fused cladding, the isotropic scanning path has a uniform distribution with a low content of the Laves phase and the lowest abrasion rate of the fused cladding layer. The reciprocating and dispersive scanning paths have intermediate abrasion rates, while the shrinkage-type scanning path has the highest abrasion rate due to its larger number of Laves phases. Therefore, a reciprocating scanning path should be selected for multi-pass cladding to reduce residual stresses in the cladding layer, and an isotropic scanning path should be selected to reduce the wear rate of the cladding layer. The results of the different scanning paths are expected to provide a theoretical basis for the selection of process parameters in the fields of surface protection and remanufacturing.

Gas nitriding-quenching (N+Q) compound treatments on GCr15 steel were carried out and compared with single processing of gas nitriding and quenching. The phases, microstructures, and the dry sliding friction properties of samples were studied. By single gas nitriding at 530℃ for 9 h, the compound layer was composed of ε phase with a thickness of about 40 μm. However, the nitride of ε phase in the compound layer were completely decomposed in N+Q compound treatment, which promoted N element to diffuse into the matrix, and the thickness of the diffusion region was about 900 μm. Compared with the single quenching hardness of GCr15 steel, the hardness of diffusion region was improved about 200 HV_0.1, because of soluble N element. However, the surface hardness dropped down, due to the porosity resulting from the decomposition of nitrides. Furthermore, under the loads of 20 N and 100 N, the dry reciprocating sliding frictions were carried out respectively. The results show that the friction co-efficients (COF) of both single gas nitriding and N+Q compound processing are lower than that of single quenching treatment. The wear resistances of N+Q compound treatment samples are improved, compared with nitriding and quenching samples at a load of 20 N, and decreases at a load of 100 N due to the surface porosity during initial steps. However, after the initial steps, the anti-wear ability of N+Q compound treatment samples increases again.

The NiCrAlY＋(ZrO₂＋Y₂O₃) thermal barrier coating was prepared on the surface of refractory steel (1Cr18Ni9Ti) by plasma spraying technique. SEM observation showed that the bonding between thermal barrier coating and substrate was good. The surface hardness of 1Cr18Ni9Ti was improved, the microhardness of coating surface was about 673HV after the thermal barrier test at 850℃. The test results showed that the thermal barrier properties were improved remarkably. The phases and microstructure of the thermal barrier coating were determined by SEM.

In the production process of a hundred-meter-long high-speed railway track, the rolling mill serves as a key component, bearing the effects of alternating high-temperature rolling parts and cooling water. It also faces significant extrusion, shear, and thermal stresses on the surface, resulting in problems such as short service life and severe roller surface wear due to failure. As a primary consumable component in the production processes of many industries, the scrapping a large number of rolls results in considerable waste of energy and resources in China. To repair the surface of scrapped rolls and improve their thermal fatigue performance, we developed the powder composition of iron-based powder, leveraging the good compatibility between the iron-based powder and the matrix material and the reduced cracking during the melting process. Considering the actual production conditions of the rolling mill, selecting an appropriate strengthening element is necessary to improve the performance of the repaired surface. Mo exhibits a good solid-solution strengthening effect and forms carbides, thereby enhancing the strength and wear resistance of the substrate. To further improve the wear resistance of the cladding layer while ensuring good thermal fatigue performance, elemental V was added to improve high-temperature stability, allowing the cladding layer material to maintain good performance at elevated temperatures. A laser cladding technique was used to prepare an iron-based coating using T504 as the base powder, with Mo and V added to the surface of a fatigue- failed 160CrNiMo roller material. The crack propagation rate and mechanism in the base material and cladding layer during thermal fatigue were analyzed using optical microscopy, scanning electron microscopy, and thermal fatigue testing machines. The results show that the average hardness of the cladding layer with Mo and V ratios of 1:0.5, 1:1, and 1:1.5 is 59.2 HRC, 59.9 HRC, and 59.1 HRC, respectively, representing an average increase of 33.4% compared to the substrate; The driving force for crack propagation during thermal fatigue tests primarily arises from the thermal stress generated by cold and hot cycles. After 2000 thermal fatigue testing cycles, the crack length in the matrix material sample measured 11.289 mm. Due to its high carbon equivalent, the brittle phase of eutectic M₇C₃, which contains a higher Cr content than the surrounding material, exhibited a different coefficient of thermal expansion. This mismatch became the main channel for crack propagation during the thermal fatigue testing process, where cracks primarily propagated in a transgranular form. The crack lengths of the samples with added Mo and V mass ratios of 1:0.5, 1:1, and 1:1.5 in the cladding layer were 3.185 mm, 16.596 mm, and 8.401 mm, respectively. The high hardness of the cladding layer, resulting from the addition of Mo and V, increased its brittleness. As the V content increased, the eutectic structure of the cladding layer gradually appeared to break down; the initial boundary became clear and blurred, compromising the integrity of the structure and leading to an increase in the number and length of microcracks. During thermal fatigue testing, the propagation of fatigue cracks was predominantly brittle and transgranular, exhibiting a rapid propagation rate. The sample completed the rapid crack propagation stage after 50-100 cycles. However, appropriate addition of V can improve high-temperature stability and result in shorter cracks. When the mass ratio of Mo to V was 1:0.5, the thermal fatigue performance of the roller material before repair improved by 71.7%. A comparison of the thermal fatigue characteristics of the iron-based coatings with different Mo and V mass ratios provides an experimental basis for selecting iron-based coating systems for roller repair.

Based on the background of the anticipated Industry 4.0 era, the promotion of “Made in China 2025” and the strategy of maritime power, traditional marine anti-fouling coating materials have gradually withdrawn from the historical stage and been replaced by new biomimetic and intelligent marine anti-fouling coating materials. However, a comprehensive and systematic review of new biomimetic and intelligent marine anti-fouling coating materials is still lacking. Therefore, this study reviews the research progress of biomimetic anti-fouling coating materials constructed by biomimetic anti-fouling strategies, such as micro-nanostructure surface, release of green anti-fouling agent, super-slippery surface, dynamic surface, and self-healing. Meanwhile, the research progress of intelligent anti-fouling coating materials formed by intelligent anti-fouling strategies, such as pH, temperature, and light response control, is reviewed. The research progress of synergistic anti-fouling coating materials constructed by the synergistic anti-fouling strategies, namely the combination of biomimetic and intelligent anti-fouling strategies, is also reviewed. Finally, the preparation methods, anti-fouling mechanisms, effects, advantages and disadvantages, and the development trends of the above coating materials are summarized. The emerging biomimetic and intelligent marine anti-fouling coating technology are currently recognized in marine anti-fouling, and has achieved good research results; however, some problems are yet to be resolved. For example, the toxic components of current coating materials have uncertainties and potential risks to the growth and reproduction of marine organisms and marine ecosystems; the surface structure of biomimetic anti-fouling coating is complex; weak anti-fouling durability, stability, and high cost. The response of intelligent anti-fouling coating to external conditions is singular; the anti-fouling stability is not high, and the intelligent anti-fouling evaluation system and mechanism are unclear. Other issues include multi-strategy combined anti-fouling coatings and limited research on the synergistic anti-fouling mechanism between various strategies. Furthermore, the future development direction of anti-fouling coating materials constructed by biomimetic and intelligent multi-antifouling strategies is suggested. In selecting coating materials, the marine environment affinity components are used to replace the toxic components to reduce the risk of toxic substance release into the marine environment; adhering to the principle of "from the ocean, to the ocean" vigorously tap the marine biological resources, extract or synthesize new and efficient bio-antifouling agents to block the related signals and metabolic pathways of fouling organisms to inhibit the deposition and attachment of fouling organisms, rather than direct poisoning, thereby reducing the genetic risk to marine organisms; strengthening the basic research of bionics and biomimetic technology, and studying the microstructure surface, metabolism, and release law and stress behavior of anti-fouling attached organisms to quickly improve the overall design level of biomimetic anti-fouling coating; an intelligent “on-off” anti-fouling system with multiple conditional response was designed, which meets the requirements of convenient and accessible practical application environment and can quickly start and stop according to the specific environment, promoting the broad application of biomimetic and intelligent marine anti-fouling coating materials; increasing the research of multi-strategy combined anti-fouling method systems, such as expanding various anti-fouling strategies and an in-depth study of the synergistic anti-fouling mechanism between various strategies to solve the problem of a single anti-fouling strategy failing to meet the requirements of long-term, stable anti-fouling in the actual complex marine environment, thus ensuring long-term stable and efficient anti-fouling of coating materials. The multi-strategy combined anti-fouling method system will become an important development trend in marine anti-fouling in the future. This study mainly proposes the guiding viewpoint of the method system of the synergistic effect of biomimetic and intelligent multi-antifouling strategies, addressing the issue of limited review articles in the industry. Given the continuous progress of science and technology, the multi-strategy joint anti-fouling method system is expected to promote new breakthroughs in the marine anti-fouling industry in China. Biomimetic and intelligent marine anti-fouling coating materials will become a major development direction of marine anti-fouling in the future. In addition, they have important reference value for the development of national defense and military, marine engineering, maritime transportation, marine fishery, and other fields.

In this work, the main content for service life of military aircraft was introduced briefly, the typical corrosion cases were illustrated, and the harm of environmental corrosion to aircraft was described. It is significant and urgent to research the anti–corrosion technique and calendar life of aircraft. The service environment, application feature and corrosion status of active military aircrafts were discussed. The main existing problems for corrosion and calendar life of active aircrafts were analyzed and the key techniques that should be studied mainly now were advanced.

The structure of BCN amorphous nano-films were studied by XPS. The characteristic peak of three elements of Ar, contamination carbon and deposited monolayer Au were considered as reference peak to correct the shift of the XPS spectra caused by charging effect during the XPS analysis process, and the results of XPS and FTIR analyses were compared to estimate the correctness of this method. The investigation results indicated that the calculated binding energy of BCN film depends on reference peak selection, and the correct structures can be obtained when the bonding energy was adjusted by selecting appropriate characteristic peak. The bonding structures of films corrected by Ar are quite similar with the results of FTIR analysis. This method is suitable for analyzing BCN films prepared in Ar-contained sputtering atmosphere, and is also suitable for analyzing the inner structure of films. There is an obvious deviation in bonding energies between the true value and adjusted by contamination carbon or by deposited monolayer Au.

Recent developments over these years on the surface treatment for aluminum and its alloys by micro-arc oxidation (MAO) were reviewed. The effects of the substrates and the electric parameters such as current density, voltage and frequency on the growth, composition, structure and properties of the MAO coatings on aluminum alloys were emphasized. The common electrolyte systems used in the MAO treatment for aluminum alloys were analyzed. The characteristics of kinetics and the growth mechanism of the MAO coatings on aluminum alloys were described. It was pointed out that the control of electric parameters and adjustment of composition and concentration of electrolyte would be the study emphases of MAO technique for aluminum alloys in the future.

Within the orbital altitude range of 180 km to 650 km, oxygen molecules in the atmosphere tend to decompose into atomic oxygen when exposed to ultraviolet light. Due to its strong oxidizability, atomic oxygen, is capable of causing erosion effects on the surface materials of spacecraft. Complex structural evolutions, such as mass loss, thickness reduction, and changes in surface morphology are involved in this process. So that performance degradation inevitably occurs, highlighting the importance of protecting the surface materials of low-orbit spacecrafts. The adoption of protective coatings is an effective way to improve the atomic oxygen protection performance of materials and ensure the long lifespan and high reliability of low-orbit spacecraft. The research progress of atomic oxygen protective coatings is briefly reviewed, and the factors affecting the performance of atomic oxygen protective coatings are studied. The results show that surface roughness, defects composition and structure of the coating have significant influences on its atomic oxygen protection effect. A rough surface of the coating has advantage in increasing the probability of collisions between atomic oxygen and surface materials, while defects in the coating provide more channels for atomic oxygen and enhance the erosion effects, and the composition and structure of the coating will affect the probability of atomic oxygen reactions. The types of space atomic oxygen protective coatings are investigated, and the characteristics of different types of coatings are analyzed. Atomic oxygen protective coatings can be divided into inorganic coatings, organosilicon coatings, and composite structure coatings. Among them, inorganic coatings are generally solid oxides with a dense structure, and this type of coatings has excellent protective performance but poor flexibility. Organosilicon coatings are mainly composed of elements such as Si, H, C, and O. Good flexibility is achieved through the formation of a polymer-like network structure in organosilicon coatings. When eroded by atomic oxygen, a dense silicon oxide layer appears during the reaction between atomic oxygen and Si atoms located at the surface of coatings, which prevents further erosion. However, under the action of high flux atomic oxygen, the coating surface is prone to shrinkage, resulting in a “tiled” surface and coating cracking. The composite structure atomic oxygen protective coatings can make up for the shortcomings of single-structure coatings and adapt to the needs of different application conditions, however, the performance of this type of coatings is highly correlated with their structure and requires. The coating preparation methods are sorted and summarized, while the advantages / disadvantages and application objects of different preparation techniques are analyzed based on a comprehensive comparison: inorganic coatings with dense morphology can be obtained through magnetron sputtering process, which is mainly suitable for preparing coatings / films on rigid or semi-rigid substrates. Plasma-enhanced chemical vapor deposition in coating preparation corresponds to lower deposition temperature, less thermal damage to substrates. And a wider application range because both inorganic coatings and organic coatings can be achieved in this way. However, due to process limitations, this technology can only be applied to planar substrates and cannot be applied to three-dimensional complex structural parts; ion beam co-deposition can conveniently prepare multi-component composite structure coatings, so it is the main preparation technology for composite atomic oxygen protective coatings; atomic layer deposition has precise coating thickness control, a dense coating structure, no pinholes and other defects, and can form a uniform film on the substrate surface with complex configurations such as steps and grooves. Moreover, it can repair the defects on the substrate surface, therefore having obvious advantages in atomic oxygen protection and achieving good atomic oxygen protection performance at a relatively thin thickness. However, the disadvantage is the low deposition rate, low efficiency, and high stress when preparing thick coatings. Cracks are prone to occur when applied on flexible substrate surfaces. The sol-gel method for preparing coating materials has a low temperature during the process, uniform coating structure, easy control of the reaction process, and low cost. However, in general, the coating thickness is relatively high, requiring tens of microns or more and high quality, which is not conducive to the light weighting of spacecraft. Therefore, it is mainly applied to small structural parts. The precursor photolysis / hydrothermal curing method requires post-treatment such as irradiation and heating when preparing coatings, and the uniformity control is more difficult when implemented on a large area. Therefore, it is suitable for local coating and repair of easily damaged areas on the surface of structural parts. The further development trend of atomic oxygen protective coatings is analyzed and introduced. The research provides the necessary research basis and reference for the atomic oxygen protection of materials for low-orbit spacecraft in China and provides research ideas for the further development of atomic oxygen protective coating technology.

Plasma Immersion Ion Implantation and Deposition technology (PIIID) can obtain a uniform and perpendicular ion implantation on the components with sophisticated shape. It has shown great potential in surface modification for industrial components. After its invention, PIIID has developed rapidly in recent years. However, in order to get wide commercial applications, the methods for high efficiency ion implantation, inner surface ion implantation and large area ion implantation should be proposed.

喷雾造粒制备莫来石粉末,采用大气等离子设备对造粒粉末进行等离子球化和涂层制备。利用激光粒度分布仪对粉末粒度分布进行测试;扫描电镜和X射线衍射仪分别表征了粉末和涂层的相组成和微观形貌。结果表明:喷雾造粒和等离子球化后的莫来石粉末粒径为正态分布;造粒的莫来石粉末主要由晶态莫来石和SiO2相组成;等离子球化后,粉末中出现玻璃态非晶相;等离子球化过程中,较小粒径粉末表面基本上完全熔融,较大粒径粉末的表面为部分熔融;同时,制备的莫来石涂层具有良好的微观形貌和较高的显微硬度;涂层经热处理后,非晶相转变为晶态莫来石,并且有部分石英相析出。

Numerical simulations are powerful tools for analyzing the rolling process of metal composite plates. However, the current numerical models for simulating the cold-rolling compounding of dissimilar metal-layered plates mostly adopt either interface binding or friction constraints. These approaches fail to accurately judge and simulate dynamic compounding at the interface, making it difficult to achieve precise predictions of the true stress-strain field, macroscopic warping, and thickness ratio of composite plates. Additionally, simulations involving high reduction rates in a single pass often suffer from severe mesh distortion and nonconvergence issues, hindering the integrated development of simulations in the field of rolling compounding. In this paper, we propose a novel numerical model to overcome these limitations. The finite element modeling of the Cu/Al plates in this model employs elongated meshes with an aspect ratio of at least 2. This improvement addresses the shortcomings of previous compounding criteria, which only considered normal forces, by incorporating tangential force constraints. This enhancement allows for a more accurate representation of the actual rolling compounding process, which involves the combined action of normal and tangential forces. The research objectives of this study are multifaceted. First, we aim to develop a robust numerical model that can accurately simulate the rolling compounding process of dissimilar metal-layered plates. Second, we seek to predict the quality of the composite metal plates in terms of their stress-strain field, warping degree, and post-rolling thickness ratio. The study's methodology involves several key steps. Initially, we developed a finite element model using elongated meshes with aspect ratios of at least 2. This choice of mesh design helps reduce mesh distortion and improves the convergence of the simulations. We then incorporated tangential force constraints into the model to address the limitations of previous models that only considered normal forces. This dual consideration of normal and tangential forces allows for a more realistic simulation of the rolling compounding process. The model's performance was evaluated through a series of simulations involving Cu/Al plates with various thickness ratios (2:4, 3:3, and 4:2) and reduction rates ranging from 40% to 60%. The simulation results were analyzed to assess the accuracy of the model in predicting the stress-strain field, degree of warping, and post-rolling thickness ratio of the composite plates. One of the key innovations of this model is its ability to mitigate severe mesh distortion and non-convergence issues that plague high-reduction-rate simulations. Using elongated meshes and incorporating tangential force constraints, the model provides a more realistic simulation of the rolling compounding process. This allows for more accurate predictions of the stress-strain field, warping degree, and post-rolling thickness ratio of the composite plate. The simulation results demonstrated that the proposed model can effectively simulate the rolling compounding process of Cu/Al plates with various thickness ratios and reduction rates. The predictions of the warping degree and post-rolling thickness ratio of the model were accurate, with errors within acceptable limits. Specifically, the error in predicting the degree of warping was less than 7.40%, and the error in predicting the post-rolling thickness ratio was generally less than 10%. This shows that the model can be used to predict the mass of the composite metal plates and has the potential to explore the internal mechanism of the rolling composite. In conclusion, the proposed numerical model addresses the limitations of existing models by incorporating elongated meshes and tangential force constraints. This allows for more accurate simulations of the rolling compounding process, leading to better predictions of the stress-strain field, warping degree, and post-rolling thickness ratio of the composite plate. The model initially solves serious mesh distortion and calculation non-convergence problems in high-pressure rate simulations and provides a reference for the process optimization of composite metal plates.

This paper introduced a new Repair Machine for Die & Mould, which adopts the technology of impulse welding based on the thought of Dual Pulse Width Modulation (DPWM). Its’ circuit was designed and emulated. The design of the repair machine for die & mould on DPWM is rational after circuit simulation.

It is often the case that extreme conditions are frequently encountered in high-tech equipment, where conventional materials often prove inadequate inmeeting the requirements of intended application. It is therefore imperative that ultra-high-performance materials and technologies be developed to tackle these challenges. In view of the demand for lubricating and wear-resistant surface technology in the development of national frontier equipment under harsh conditions, this study presents a review of recent advancements in this special materials field, with particular focus on the aerospace and nuclear energy sectors. It takes the adhesive solid lubricant coatings developed by our team as object, emphasizing key common technical challenges and addressing practical engineering issues. Including key technologies such as the modification of tough and strong integrated basic resins, the improvement of atomic oxygen resistance by POSS modified resins, the design and adaptive control of lubrication components over a wide temperature range, the design of surface and interface of coatings resistant to special media, and the control of system compatibility. Additionally, a compilation of representative products developed based on this basis is listed, together with an illustration of their exemplary applications in addressing friction-related challenges under extreme conditions within high-tech equipment domains. The application in key components of aircraft and aviation engines, in key components of rockets and satellites, especially in the docking mechanism of space stations, has solved the lubrication and wear problems of components under many extreme conditions in aerospace. This underscores the indispensable and crucial role played by advanced lubrication and wear-resistant surface engineering technologies in driving forward national advancements in high-tech equipment. Finally, considering future developmental requirements for cutting-edge manufacturing at a national level, potential directions for further advancing extreme condition lubrication and wear-resistant surface engineering technologies are explored. This article provides a comprehensive understanding of the demand for extreme condition lubrication and wear-resistant surface engineering technology in the national high-tech field, promotes the high-tech application of related technologies and products, and develops higher limit performance lubrication and wear-resistant surface engineering technology for future high-tech equipment needs. It offers a valuable reference point and provides guidance significance on these matters.

Aluminum-based intermetallic compounds are recognized for their excellent high-temperature mechanical properties, high resistance to oxidation and corrosion at elevated temperatures, and low density. These characteristics make them suitable for a broad range of applications, including protective coatings and structural components in aerospace and other industries. High-energy-beam additive manufacturing technologies, such as laser and electron beam melting processes, are effective for the rapid fabrication of complex metal structures. However, depositing aluminum-based intermetallic compounds remains challenging due to their complex phase structures and inherent brittleness, which often lead to flaws and defects, particularly cracks. Cold spraying, a process characterized by low processing temperatures and high deposition rates, shows significant potential for the low-heat-input fabrication of aluminum-based intermetallic compounds. This paper summarizes and analyzes recent advancements in the preparation of aluminum-based intermetallic compounds using cold spraying. Effects of powder design and fabrication routes on deposition behavior and deposit properties are discussed. These routes include intermetallic compound powder deposition, mixed elemental metal powder cold spraying followed by heat treatment, and cold spraying of mechanically ball-milled pseudo-alloy powders with subsequent heat treatment. First, the deposition behavior of intermetallic compound powders is reviewed and discussed. In the cold spraying process, successful deposition and bonding of spraying particles rely on plastic deformation induced by particle impact. However, due to the intrinsic brittleness of intermetallic compounds at room temperature, it is difficult to deposit particles directly using intermetallic compound powders as feedstock. In practice, when relatively soft materials are used, only a single layer of intermetallic particles can be mechanically embedded into the substrate layer. Subsequent spraying does not contribute to building up of the deposit because achieving successful bonding between intermetallic particles is highly challenging. Although high gas temperatures, even up to 1 000 ℃, are used to soften intermetallic particles, depositing a thick, high-quality deposit remains elusive. Thus, preparing intermetallic deposits using intermetallic feedstock powders continues to be a challenge. To address this issue, an alternative strategy involving the formation of intermetallic compounds during or after deposition has been extensively investigated. Following this strategy, mechanically mixed powders containing aluminum (Al) and other elemental powders, such as iron (Fe), nickel (Ni), or titanium (Ti), are used as feedstock materials. Due to the excellent plastic deformability of elemental metal powders, deposits containing mixed elemental metal particles can be easily deposited by cold spraying at relatively low gas temperatures and pressures. Post-spray heat treatment or annealing is then performed to activate interdiffusion between the Al and Fe / Ni / Ti phases, facilitating the formation of intermetallic compounds. However, the higher deposition efficiency of Al powder compared to Fe / Ni / Ti powders often results in cold-sprayed composite deposits with a higher Al content than the feedstock powder, complicating precise control of the chemical composition. This challenge is particularly pronounced when the feedstock powder contains more than three elemental metal powders. Additionally, during heat treatment, the long diffusion paths required for intermetallic compound formation frequently lead to the creation of numerous Kirkendall pores, and achieving a single intermetallic phase proves difficult. To overcome these challenges, a method involving the cold spraying of mechanically milled pseudo-alloy powders, followed by heat treatment, is proposed. By controlling the intensity and duration of high-energy ball milling, pseudo-alloy powders with alternating submicron lamellae of various metals can be prepared from mechanically mixed metal powders. The composition of the pseudo-alloy powder can be precisely controlled by adjusting the proportions of the raw materials. Moreover, the pseudo-alloy powder retains the plastic deformation capability of the original elemental metals, ensuring efficient deposition during cold spraying. The fine microstructure of the alternating submicron metal lamellae significantly shortens diffusion paths during heat treatment, effectively mitigating the formation of Kirkendall pores in the deposit. Finally, the effects of post-treatments such as friction stir processing (FSP) and hot isostatic pressing (HIP) on the microstructure and properties of the deposit are summarized. FSP treatment greatly refines the microstructure of deposits sprayed with mechanically mixed elemental metal powders, resulting in structures featuring alternating submicron metal lamellae and partially formed intermetallic compounds. This refinement significantly shortens diffusion paths between phases and prevents the formation of Kirkendall pores. However, it is challenging to process parts with complex shapes using this method. In contrast, HIP applies isostatic pressure during treatment, closing Kirkendall pores and making it suitable for parts with complex geometries. Overall, cold spraying of mechanically mixed elemental metal powders followed by HIP treatment, as well as cold spraying of mechanically milled powders combined with subsequent heat treatment, have been shown to produce aluminum-based intermetallic compounds with low porosity and high hardness. By comparing and analyzing the advantages and limitations of different technological routes, this study aims to provide guidance for the cold-spraying additive manufacturing of aluminum-based intermetallic compounds.

采用化学浴沉积法(CBD)在硫酸镉、硫脲、氨水、氯化铵溶液体系中制备了CdS薄膜,研究了水浴温度对CdS薄膜的生长过程和物理性能的影响。试验表明,CdS薄膜的生长速率随着水浴温度提高而显著增加,薄膜从疏松变的致密,但是过高的水浴温度会导致表面晶粒变的粗糙;薄膜的结晶程度随着水浴温度提高而增强,择优取向明显;制得的CdS薄膜均有较高的光透过率,随着水浴温度的提高,薄膜厚度增加,透过率在波长560nm处出现峰值;所得薄膜均是富Cd的,且随着水浴温度的提高Cd含量也增加;薄膜的暗电导率约为10-5～10-4Ω-1cm-1,比光电导率小2～3个数量级,电导率与水浴温度没有明显对应关系。

Before 1990s, under the cyclic normal tensile stresses, the fatigue fracture mode for most of circular suspension springs in automobile subjected to torsion fatigue load was in normal tensile fracture mode (NTFM) and the fracture surface was under 45° diagonal. Because there exists the interaction between the residual stresses induced by shot peening and the applied cyclic normal tensile stresses in NTFM, which represents as "stress strengthening mechanism", shot peening technology could be used for improving the fatigue fracture resistance (FFR) of springs. However, with the rapid development in car's structure, the designed torsion fatigue load has been increased steadily since the beginning of 21 century. Therefore, the fatigue fractures occurred of peened springs from time to time are in longitudinal shear fracture mode (LSFM) or transverse shear fracture mode (TSFM) in addition to regular NTFM, which leads to a remarkable decrease of FFR. The phenomena hard to understand has been rarely happened before. At present there are few literatures concerning this problem among springs manufacture industry involving shot peening technology. By means of logical thinking and force analysis, it is found that there is no interaction between the residual stresses by shot peening and the applied cyclic shear stresses in the shear fracture mode. This means that the effect of "stress strengthening mechanism" for improving the FFR of the shear fracture mode is disappeared basically. According to the shot peening strengthening principle presented by the authors, both of residual stress and cyclic plastic deformed modified microstructure are induced synchronously like "twins" in the surface layer of a spring. It has been found by means of force analysis that, instead of "stress strengthening mechanism", "structure strengthening mechanism" produced by the modified microstructure in the "twins" can improve the FFR of the shear fracture mode. It is also shown that the optimum technology of shot peening strengthening must have both "stress strengthening mechanism" and "structure strengthening mechanism" simultaneously so that the FFR of both NTFM and the shear fracture mode can be improved more effectively by shot peening.

Additive manufacturing technology can realize the integral molding of complex components of ceramic materials, but defects exist, including the “step effect” multiphase distribution, and porosity on the surface of the components. Moreover, subsequent precision machining struggles to meet the urgent demand for high-performance silicon-carbide ceramic components for space optical detectors and semiconductor manufacturing equipment. Therefore, this study proposes a novel approach by which to repair surface defects in ceramic additive manufacturing using the chemical vapor deposition (CVD) of high-purity, high-density silicon carbide coatings. However, the proposed method still faces problems of interfacial bonding with the additive ceramic substrate and the growth pattern of the coating. Hence, the effects of the deposition temperature on the interfacial bonding, micromorphology, surface hardness, and machinability of chemical vapor-deposited silicon carbide on additive manufacturing ceramic surfaces were systematically investigated. This study used rapid laser prototyping and the silicone infiltration composite method to manufacture silicon carbide ceramic substrates and prepare silicon carbide coatings via chemical vapor deposition. The silicon carbide coatings were deposited at different temperatures of 1 200, 1 300, 1 400, and 1 500 ℃. The coatings were then deposited on the surfaces of ceramic substrates at the same temperature. The effects of the deposition temperature on the hardness, deposition efficiency, interfacial bonding, microstructure, and processability of the SiC surface coatings were systematically investigated using various techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), surface roughness measurements, micro-computed tomography (micro-CT), and scratch tests. The results showed that the hardness of the additively fabricated SiC ceramic was only 1 226 HV_0.5 before any coating was deposited, and the roughness after polishing was 1 980 nm. Because of the presence of multiple phases, the roughness was too high to achieve a mirror effect. At a deposition temperature of 1 200 ℃, a peak of free silicon (Si) appeared in the coating owing to the high precursor gas concentration. However, the temperature was insufficient to promote uniform surface deposition, which resulted in an apparently homogeneous deposition in which free Si atoms in the gas phase were deposited directly onto the substrate. As the deposition temperature increases, the deposition rate accelerates, and the critical nucleation radius of the new phase gradually increases. The critical nucleation free energy also increases, resulting in the formation of larger SiC grains. The Si-C bonds within these grains remained intact, contributing to the overall hardness. However, at an excessively high deposition temperature, pores begin to form between the grains, resulting in low density and high porosity of the substrate and coating. Despite these problems, the silicon carbide coatings deposited at all temperatures formed good bonds with additively fabricated ceramic substrates. Notably, as the deposition temperature reaches 1 400 ℃, the silicon in the substrate begins to evaporate, and defects and porosity appear on the substrate surface. These defects provide additional nucleation points for the coating, and the morphology of the coating at the interface becomes columnar. As the coating grows to a certain thickness, it transforms into a dense structure. The columnar crystals significantly enhance the bond strength of the coating and improve its surface workability, which reduces its roughness to 9.08 nm. After polishing, the coating exhibited a mirror-like finish at all deposition temperatures. Thus, this study demonstrates that the application of CVD SiC coatings can significantly improve the surface quality of additively manufactured ceramics. This approach provides a theoretical basis for engineering applications of high-performance ceramic components in advanced devices.

3D-printed silicon carbide (SiC) ceramics have excellent qualities such as high strength and temperature resistance and they permit flexible molding of complex shapes, leading to their wide use in energy processing and advanced aerospace applications in recent years. However, they have poor surface abrasion resistance. Using atmospheric plasma spraying (APS) is an economically feasible method for applying high-temperature abrasion-resistant coating on the surface of parts. Among the common self-lubricating wear-resistant coatings, YSZ coating, with its excellent high-temperature stability and oxidation resistance, is generally used in high-temperature environments. However, to improve the performance of the spraying process and reduce friction, a second phase is often added. This paper proposes (1) doping the coating with both low- and high-temperature lubricants to enable wide-temperature lubrication, (2) adding alumina to reduce the melting point of the powder and improve the coating densification, and (3) using a sol-gel-coated powder to improve the bonding between the base and second phases of the coating. In this study, three composite powders with different compositions of YSZ-Al₂O₃-CaF₂-C were prepared using the sol-gel method and centrifugal atomization drying. The corresponding composite coatings (Ca0C0, Ca5C10, and Ca10C5) were deposited on the surface of 3D-printed SiC ceramics using the APS technique. The microstructures, friction properties, and wear mechanisms of the composite coatings were studied at room temperature and 600 ℃. The results show that the coatings have a typical laminated structure. Both the coatings and abrasion marks were primarily composed of YSZ, Al₂O₃, and m-ZrO₂ phases, with CaF₂ and C phases in Ca10C5 and Ca5C10 coatings. No other chemical reactions occurred during the coating application or owing to friction. The Ca0C0 coatings without CaF₂ and C lubrication phases had the highest hardness, lowest wear rates, and largest friction factor at room temperature and 600 ℃. The strong bonding of the coating to the friction partner at 600 ℃ led to a friction coefficient of more than 1. The stabilized friction factor of Ca10C5 and Ca5C10 coatings were, respectively, 0.239 and 0.130 at room temperature and 0.175 and 0.288 at 600 ℃. The friction factor of Ca5C10 and Ca10C5 coatings considerably reduced upon the addition of CaF₂ and C lubrication phases at both room temperature and 600 ℃, reflecting improved self-lubricating properties. However, the addition of the lubrication phases led to a decrease in the hardness of the coatings and an increase in the porosity defects inside the coatings, accompanied by an increase in wear rate. The Ca5C10 coatings with higher C additions were more prone to abrasive debris generation because of the higher volume fraction of C and lower hardness, resulting in higher wear rates. Based on the abrasion mark morphology, the wear mechanism of the coating was concluded to be primarily adhesive and abrasive. The YSZ-10Al₂O₃-10CaF₂-5C coating had a lower friction factor and wear rate (1.02×10^-5 mm³ / (N·m) at room temperature and 0.84×10^-5 mm³ / (N·m) at 600 ℃) compared with YSZ-10Al₂O₃-0CaF₂-0C and YSZ-10Al₂O₃-5CaF₂-10C coatings in this study. This implies that YSZ-10Al₂O₃-10CaF₂-5C coating has good self-lubricating and wear-resistant properties and can well improve the surface properties of 3D-printed SiC.

表面纳米化可以显著改善金属材料的表面力学性能,并促进氮、铬等原子的热扩散,文中尝试采用表面纳米化技术改善金属基体/硬质薄膜的力学性能。对304不锈钢采用表面机械研磨处理获得纳米晶粒表层,采用多弧离子镀镀方法在表面纳米化和粗晶粒的304不锈钢基体上沉积CrN薄膜。对两种膜基体系采用X射线衍射、显微硬度测试、压入法和划痕法膜基结合性能评价。结果表明,表面纳米化影响了CrN膜层的组织结构,明显提高了膜基体系的硬度和承载能力,还改善了膜层的韧性,膜基结合性能也得到提高。

Inspired by Nepenthes pitcher plants, slippery liquid-infused porous surfaces (SLIPS) were first created in 2011 to offer a novel approach to surface engineering. Unlike conventional superhydrophobic surfaces (SHS), which rely on air lubrication, SLIPS utilize liquid lubrication with superior durability and pressure stability. With such advances, SLIPS possess outstanding liquid and ice repellency, self-healing, and enhanced optical transparency, which can be implemented in a wide range of energy applications, such as industrial anti-icing, anti-fouling, anti-frosting, and droplet-based power generation. Because most industrial application scenarios for SLIPS frequently encounter impacts of droplets, a mechanistic understanding of the dynamic interactions between SLIPS and impacting droplets is essential for the effective use of SLIPS under specific application conditions. This review systematically examines droplet impacting dynamics on SLIPS. In section 1, we introduce the thermodynamic conditions required to form effective SLIPS and their fabrication methods. There are two major criteria to achieve stable SLIPS: 1. lubricant spreading on the substrate, characterized by the spreading parameter (S) and 2. stabilization by van der Waals forces, characterized by the disjoining pressure or corresponding Hamaker constant (A). The fabrication of SLIPS involves structural treatments on substrates that are followed by chemical functionalization and the final lubrication selection. Based on the substrate structure, SLIPS can be categorized into 1D-SLIPS, 2D-SLIPS, and 3D-SLIPS based on the structural hierarchies varying from one-dimensional mono-molecule layers to two-dimensional micro- / nano-surface structures to three-dimensional crosslinked polymer matrices, respectively. In section 2, we summarize the dynamic behaviors of droplet impacts on SLIPS, including deposition, complete rebound, partial rebound, jet, and splash behaviors under conditions with different Weber numbers or other related dimensionless numbers. As the Weber number increases, the dynamic behaviors of droplets impacting SLIPS transitions from deposition to rebound and eventually to splash. The higher Weber number of a droplet indicates higher inertia before impacting the surface, which introduces stronger inertial forces to overcome the capillarity of the droplet. Eventually, these properties force the droplet to splash into smaller drops. Compared with many solid surfaces, SLIPS demonstrate a higher probability of droplet rebound, resulting in their advantages in the applications of anti-icing and anti-frosting. In section 3, we analyze the spreading dynamics, retraction dynamics, and contact time of SLIPS. In general, the droplet impacting on SLIPS experiences spreading and retraction processes. During the spreading process, the diameter of the droplet in contact with the surface gradually increases until the droplet spreading diameter reaches its maximum, driven by inertial forces. Subsequently, the droplet enters the retraction process under capillary and viscous resistant forces. The maximum spreading diameter can be scaled as β_max ~ We^1/4 in most conditions. Moreover, the retraction dynamics dominated by viscous forces are affected significantly by the lubricant viscosity. With the increase of the contact angle and the decrease of the lubricant viscosity, the retraction velocity tends to be higher. Further, the contact time is mainly affected by the diameter of the droplet and the lubricant viscosity but is independent of the droplet impact velocity. Compared with superhydrophobic surfaces, the contact time on SLIPS is generally longer owing to viscous retention. In section 4, the different application potentials of SLIPS are systematically summarized. The stability and self-healing of SLIPS are advantageous for the applications, including anti-icing, anti-fouling, fog harvesting, and electricity generators. These applications with SLIPS may revolutionize the modern biomedical devices, solar panels, wind turbines, and small-scale energy generators. Finally, the dynamic characteristics of droplets impacting the SLIPS and the research direction are summarized and prospected. This review provides a comprehensive understanding of the key physical principles underlying the phenomena of droplet impacts on SLIPS as well as further application conditions of SLIPS in energy industries, including industrial anti-icing, defrosting, surface-enhanced heat transfer, and electricity generation from droplets.

Thermal barrier coatings serve as a prevalent advanced heat protection method in aviation engines. The working environment for the coatings becomes increasingly challenging with a rise in engine operating temperatures. Investigating the failure modes of the coatings under high-temperature and high-temperature gradient conditions is essential to improve the operational lifespan of the coatings. A ceramic coating with a thickness of 0.12 mm, comprised of Gd₂O₃-Yb₂O₃-Y₂O₃ co-doped ZrO₂, was produced on the GH3536 substrate using the atmospheric plasma spraying technique. A burner rig test device has been designed to simulate the service environment of coatings. This generates a super high-temperature flame by burning a mixture of aviation kerosene and oxygen, ensuring high temperatures on the sample surface. The sample is of a hollow structure with high-pressure cooling water flowing inside, which ensures low temperatures on the back of the sample, thus generating a severe temperature gradient. The use of various characterization methods allowed for an analysis of the microstructural changes in the coating, leading to a discussion of the failure mechanisms of the coating under high temperature and high temperature gradient conditions. The results show that after burner rig test with surface temperature of about 2350 ℃, the coating life of single long-time test is greater than 1200 s, and the coating life of multiple short-time test is 3 times. The coating showed obvious gradient sintering along the thickness direction. The top area of the coating is heavily sintered, which is called the sintered zone, and the porosity and grain size are distributed in gradient along the thickness direction. After multiple 25 s tests, there was an observed increase in the depth of the sintered zone, a higher quantity of vertical cracks, and an expansion in both the width and length of transverse cracks as the number of tests increased. Furthermore, the thermal growth oxide (TGO) transitioned gradually from alumina to spinel, and there was an expansion of the micro-transverse cracks formed by TGO. After the 1200 s test, the coating maintained a singular cubic phase and demonstrated excellent stability at high temperatures. In contrast to the single 25 s test, the sintering depth increased, leading to a higher number of vertical cracks. However, the quantity of transverse cracks remained consistent, confirming that transverse cracks arise from thermal-mismatch stress during repetitive thermal shock processes. In summary, the failure of the coating under high temperature and high temperature gradient conditions can be attributed to a combination of high-temperature sintering, thermal-mismatch stress, and TGO. The failure process can be summarized as the rapid propagation of early-stage vertical cracks caused by high-temperature sintering, the generation of intermittent transverse cracks at the interface due to thermal mismatch stress. The micro-transverse cracks produced by the thermal growth oxide connect the intermittent transverse cracks at the interface, and the connection through the vertical cracks and the continuous transverse cracks causes the coating to finally fall off. Failures occur earlier and the failure mechanism is more complex under high temperature and high-temperature gradient conditions compared to that in conventional thermal shock tests. The research results provide some support for the development of new thermal barrier coatings. The premature failure of coatings can be alleviated by improving the sintering resistance of coatings, increasing the thickness of coatings appropriately and designing multilayer structures.

According to technological condition of brake disc of deep–well drilling rig, laser cladding Fe–based alloy coating and Fe–based alloy composite coating with Cr₃C₂ particles on 35CrMo substrate were obtained. The microstructure, micro–hardness and sliding wear resistance of the coatings were studied. The results show that the Fe-based coatings are solidified in hypo–eutectic way, and network eutectic structure existed in the primary dendrite solid solution. The main phases of Fe coating were γ–Fe、Cr₇C₃ and Cr–Fe solid solution. Most of Cr₃C₂ particles in Fe-based composite coating are mostly dissolved. The basic solidifying characteristic of Cr₃C₂/Fe is nearly unchanged. The dendrite of the composite coatings became to be finer. The phases of Cr₃C₂/Fe composite coatings were composed of γ–Fe、Cr₇C₃、Cr–Fe solid solution and Cr₃C₂. The micro–hardness and friction and wear properties of Cr₃C₂/Fe composite coating were obviously better than that of Fe coatings.

The characteristics of laser cladding and laser remanufacturing technology are introduced. Laser cladding technique is one of the basic techniques of laser remanufacturing technology. It has many characteristics such as high bonding intensity, small heat affect zone, small heat deformation, good automation control etc. The combination of many processing techniques, which mainly consists of laser cladding, and remanufacturing products form Laser remanufacturing technology. It is the important part of remanufacturing technologies. It has characteristics of high quality, high efficiency, economized energy sources, economized material and environment protection. The rise and development of this technology offers a new technical means for the repairing and rebuilding of important mechanism equipments made in China and some importing products. In China, laser remanufacturing technology is widely applied to many industries such as petroleum and chemical, metallurgy, electric power etc. Some representative examples of important mechanism equipments processed by laser remanufacturing are illustrated in this paper. Developing laser remanufacturing of important mechanism equipments has wide market in China. Further more it has important economic and societal benefit.

The working environment of the inner surfaces of tubes in industrial production is harsh, necessitating higher performance against corrosion, friction, and wear. To improve the properties of the inner surfaces of tube and barrel parts, a high-power impulse magnetron sputtering (HiPIMS) coating method with an auxiliary anode is proposed. The auxiliary anode was first placed near the tube tail to attract plasma into the inner part of the tube. Chromium (Cr) coating was then deposited on the inner wall of a carbon steel tube with a diameter of 40 mm and a length of 120 mm. The effects of the auxiliary anode voltage on the discharge characteristics of the Cr target as well as the structure and mechanical properties of the Cr coating deposited on the tube’s inner surface were explored. The accessible depth of Cr deposition inside the tube was established. The plasma distribution inside the tube following the addition of the auxiliary anode was analyzed and a theoretical model was developed. The experiments demonstrated that the substrate current increases with higher auxiliary anode voltages, particularly at the tube tail position. When the auxiliary anode is positioned at the end of the tube, it attracts electrons deeper into the tube, resulting in increased ionization of additional ions and electrons during their movement. The ions generated by ionization are attracted to the inner wall of the tube by the negative charge carried by the tube. This can be inferred by comparing the emission spectral intensity curve between the nozzle and the tube tail. At the port position, when the auxiliary anode voltage is 20 V, the Ar+ feature peak value is the lowest, whereas the corresponding Cr* feature peak value is the highest. We infer that at 20 V, most of the energy is absorbed by the excited particles. However, under the influence of the auxiliary anode, electron escape is accelerated, inhibiting the discharge. The Cr film deposited at the tube port has a columnar structure, as shown by the cross-section morphology of the film deposited at different auxiliary anode voltages. At higher auxiliary anode voltages, the columnar crystal width decreases, and the deposited film becomes denser. As the auxiliary cathode voltage increases, the overall depth of the deposited chromium layer in the tube also increases. However, the deposition rate decreases with an increase in auxiliary anode voltage. This may be due to the higher energy of the particles that derives from the increased auxiliary anode voltage, which leads to the film densification and enhanced etching effects, thereby decreasing the deposition rate. The coating hardness and elastic modulus of the Cr film both increased initially and then decreased with increasing auxiliary anode voltage. At an auxiliary anode voltage of 40 V, the Cr coating achieved the best depth with the highest hardness and elastic modulus. Under HiPIMS discharge conditions, the effects of the auxiliary anode on the plasma can generally be summarized. First, by attracting electrons, the auxiliary anode regulates the direction of plasma’s movement. The plasma concentration can be greatly increased by the additional anode. An additional anode at the tube's end modifies the distribution of electric field lines in the vacuum chamber, reducing the number of escaping electrons. Second, high-density, high-energy plasma preferentially forms along the tube axis towards the auxiliary anode at the tube’s end, promoting further collision ionization of neutral particles inside the tube and delaying the decrease in plasma density caused by the increased distance from the target surface. The Cr coating deposited on the inner surface of the tube can be widely used in harsh environments.

Titanium dioxide nanotubes (Titanium dioxide nanotubes, TiO₂ NTs) have garnered significant attention in recent years owing to their unique nanostructures, high specific surface areas, and exceptional antibacterial and drug-release capabilities. As innovative surface-modification materials, TiO₂ NTs show great promise for use in biomedical applications, particularly in infection control and drug delivery. The remarkable properties of TiO₂ NTs, including their abilities to interact with biological systems, have made them a focal point of research for the development of new therapeutic strategies, particularly for combating bacterial infections. This review systematically examines the fabrication methods of TiO₂ NTs and their applications in the antibacterial field, focusing on their roles in controlling bacterial infections and regulating drug release mechanisms. The methods used to fabricate TiO₂ NTs, such as anodization, sol-gel processes, and hydrothermal synthesis, are critical for controlling their size, morphology, and surface properties, all of which directly influence their performance in various biomedical applications. These fabrication techniques allow for precise control over nanotube structures, which optimizes their drug-loading capacity and ensures their effectiveness in both infection prevention and controlled drug release. Moreover, TiO₂ NTs are highly effective at preventing bacterial adhesion and biofilm formation, which are key challenges in medical treatments. Further, TiO₂ NTs can be functionalized by loading various antibacterial agents, such as antibiotics, silver nanoparticles, and other bioactive compounds, to enhance their therapeutic effects. This review discusses various loading techniques, including physical adsorption, layer-by-layer self-assembly, and solution impregnation, for improving the efficiency of drug delivery. Physical adsorption is a simple and widely used technique for loading antibacterial agents, where the agents are adsorbed onto the surfaces of nanotubes. In contrast, layer-by-layer self-assembly creates a more complex structure with multiple layers, thus allowing for a more controlled and sustained release of drugs. Solution impregnation, which is another important technique, facilitates the incorporation of therapeutic agents into nanotubes and ensures that the drugs are released gradually, thus enhancing their antibacterial effects over an extended period. Additionally, sealing technologies are crucial for enhancing the drug release efficiency. Sealing methods typically involve the use of polymers or composite materials that encapsulate drugs, which prevents their premature release and ensures a more controlled and sustained-release profile. These sealing technologies improve the stability and performance of TiO₂ NTs in biological environments and thereby optimize their therapeutic benefits. Despite the promising antibacterial properties and biocompatibility of TiO₂ NTs, their practical applications face several challenges. Issues such as the structural stability of TiO₂ NTs in biological environments, precision of drug release, and long-term safety must be addressed. The degradation and morphological changes in TiO₂ NTs in biological fluids can compromise their functionality and biocompatibility. Moreover, ensuring precise drug release is challenging because the careful design of the nanotube structure and loading methods are required. Long-term safety, particularly the potential toxicity of TiO₂ NTs and their degradation products, must be further evaluated to ensure their safe use in medical applications. Future research should focus on optimizing the design of TiO₂ NTs by exploring new fabrication techniques and developing multifunctional composite materials that combine TiO₂ NTs with other materials, such as polymers, natural biomolecules, or nanoparticles. These composite materials can enhance the stability and drug loading as well as control the release of TiO₂ NTs, which thereby expands their applications in a variety of therapeutic contexts. Furthermore, clinical trials are required to validate the long-term safety and efficacy of TiO₂ NTs in real-world medical applications. By addressing these challenges and advancing the development of TiO₂ NTs, their potential for widespread use in the medical field can be realized to thereby provide innovative solutions for infection prevention, controlled drug delivery, and other biomedical treatments.

This study explores the tribovoltaic effect and its applications in energy harvesting and smart sensors. The tribovoltaic effect occurs when a sliding motion at a semiconductor heterojunction interface generates friction, which excites electron-hole pairs at the interface. Under the influence of an electric field at the semiconductor interface, these electron-hole pairs undergo directional migration, generating a direct current (DC), a process referred to as the tribovoltaic effect. Devices that harvest mechanical energy based on the tribovoltaic effect are known as tribovoltaic nanogenerators (TVNGs). TVNGs can directly output DC and exhibit low-impedance output characteristics, making them a subject of widespread interest. This paper first introduces the meaning of the tribovoltaic effect and summarizes the key scientific issues involved in its research: the mechanisms of electron-hole pair excitation and the formation of the interface electric field. These issues are critical for understanding the potential of the tribovoltaic effect and for optimizing the performance of TVNGs. Specifically, this research identified that the interaction effect in energy harvesting and smart sensing, with a particular focus on optimizing the TVNG performance. This study discusses the relationship between semiconductor properties and frictional forces that play a significant role in the excitation of electron-hole pairs, while the interface electric field is crucial for the separation and migration of these carriers. Understanding these mechanisms is essential to improving the efficiency and stability of energy conversion in TVNGs. Next, this study explores the applications of the tribovoltaic energy transmission laws involved in the tribovoltaic effect and highlights several challenges, including tribological issues and surface/interface engineering problems. This study proposes that the asymmetry in the geometric structure of materials and friction-induced asymmetry at the interface can significantly contribute to the tribovoltaic effect. These factors were hypothesized to influence the output efficiency and performance of TVNGs, suggesting that a more thorough understanding and control of these variables are necessary to optimize the device performance. This study also emphasized the importance of surface modification techniques and the impact of material properties on the tribovoltaic effect. By altering the surface structure and interface properties of materials, for instance, through doping or chemical treatments, it is possible to enhance the energy-harvesting capacity of the tribovoltaic effect. Furthermore, this study suggests that advancements in tribological research, including the understanding of friction and wear at the interface, are essential for optimizing TVNGs for real-world applications. By improving the surface roughness, frictional behavior, and chemical interactions at the interface, it is possible to maximize the efficiency of the tribovoltaic energy conversion process. Finally, this study discusses future research directions for the tribovoltaic effect, predicting that its study will become increasingly diversified and intelligent. The future of tribovoltaic research will focus on material optimization, specifically enhancing the stability, output power, and durability of TVNGs. These advancements are expected to be key factors driving the development of TVNGs, enabling their widespread use in practical applications. The future of tribovoltaic technology also lies in its potential to play a critical role in smart sensors, environmental monitoring, and wearable devices, with applications extending to self-powered systems and energy-efficient technologies. By improving the material properties and optimizing the overall performance of TVNGs, the tribovoltaic effect is expected to contribute significantly to the development of next-generation energy-harvesting devices. In conclusion, the tribovoltaic effect holds great promise for energy harvesting and smart sensor applications. Future research efforts will focus on improving the performance, stability, and durability of TVNGs, which are crucial for their practical deployment in various industries. The ongoing advancements in materials science, surface engineering, and tribological research are essential for achieving these goals and ensuring the successful integration of tribovoltaic technology into real-world applications.

Hydraulic actuators are widely used in aircraft wings, doors, and landing gears. The reciprocating seal is a common seal type. Seal failure can significantly affect aircraft mission execution and flight safety. The surface roughness of the seal pair is a major controllable parameter in engineering and greatly influences sealing performance. Therefore, analyzing the effect of surface roughness on the sealing performance of actuators is both theoretically and practically significant. The Al₂O₃ oxide film formed on the surface of aluminum alloys after hard anodic oxidation has certain wear resistance, insulation, and corrosion resistance, making it widely used in aviation hydraulic systems. However, the hard anodized film (hard oxygen film) has problems such as high porosity, roughness, and friction coefficient, which can exacerbate wear and tear on the friction mating surfaces, severely limiting its practical service. Hard anodization of aluminum alloy is a dynamic process involving the formation and dissolution of the film layer in a low-temperature sulfuric acid solution. The film layer is generally divided into a compact layer adjacent to the substrate and a looser layer extending outward. Consequently, the surface hardness is low, and the roughness is inadequate. An in-situ synthesis technology is utilized to enhance the surface roughness of the aluminum alloy hard anodized film and improve its friction-reducing performance, thus meeting the service requirements of the new generation of aeronautical actuators for weight reduction and high mobility. First, wed added 15-20 mL / L of PTFE (Polytetrafluoroethylene) concentrated dispersion liquid and a proper amount of composite surfactant into the anodizing bath liquid. We then stirred it for 30 min using a direct current constant current method at a current density at the beginning of hard anodic oxidation of 0.5-1 A / dm². The current density was increased every 5 min until the desired current density was reached, where the film thickness required by the process was maintained to complete the anodic oxidation. During the hard anodizing of the aluminum alloy composite PTFE, negatively charged PTFE particles were pretreated with a composite surfactant and moved towards the surface of the aluminum alloy substrate under the action of an external electric field. As the oxide film continuously formed, the PTFE particles were absorbed and encapsulated in the film. The pores of the film layer were nearly filled with PTFE, where the PTFE was fully dispersed in the oxide liquid. The particles have a heat absorption function, effectively dissipating Joule heat from the substrate surface. Reducing the dissolution rate of the composite oxide film facilitated the formation of a low porosity and relatively compact film layer. This involved preparing the aluminum alloy composite PTFE hard oxygen film layer and detecting and analyzing its hardness, thickness, cross-sectional morphology, and phase composition. The relationship between the polishing amount and the roughness of the film was analyzed by using a three-dimensional roughness tester. Finally, the wear resistance of the friction pair with different roughness levels was verified through engineering simulation using an abrasion tester. The results showed that the hardness of the aluminum alloy composite PTFE hard oxygen film was higher than that of the hard anodized film, with surface roughness reduced from Ra2.4 μm to Ral.0 μm. Following 10 μm polishing, the surface roughness was less than Ra0.2 μm. Under the same load and time conditions, the friction coefficient of the composite film pair and the wear rate of the friction pair were both lower, at 0.08 and only 2.10 × 10^-7 mm³ / Nm, respectively. No peeling was observed in the product’s functional test, and the wear amount was minimal, meeting the product’s performance requirements. In addition, the product (aluminum alloy actuator parts with composite PTFE hard oxygen film) exhibited a self-polishing effect during actual use, which helps shorten the production cycle and significantly reduces costs. The friction and wear behaviors of hard oxygen film layers and composite PTFE hard oxygen film layers were compared and analyzed using the friction and wear pair of a piston (7075)-sealing ring (4FT-32) in an aeronautical hydraulic actuator. This analysis provides data and testing support for the design and treatment of aluminum alloy cylinder-piston pairs and other relevant friction pairs with different application requirements, facilitating the engineering implementation and application of friction pairs in actuating system components.

Aluminum alloys are widely used in ships and offshore platforms owing to their high fatigue strength, excellent corrosion resistance, welding performance and cold workability. Although the surface of the aluminum alloy usually forms an oxide film in natural environments, the film is thin and can easily be damaged during application, resulting in damaging the substrate. Therefore, preparing anti-icing, anti-corrosion and self-cleaning superhydrophobic coatings on aluminum alloy substrates is important for improving their performance and expanding their application fields. Superhydrophobic surfaces are with a water contact angle exceeding 150° and a roll-off angle below 10°. Inspired by superhydrophobic surfaces of nature, researchers have successfully prepared and developed various artificial superhydrophobic coatings that can be applied in various fields, such as self-cleaning, anti-corrosion, and anti-icing. To date, many methods for preparing superhydrophobic coatings with micro-nano structures and low-surface-energy, such as spraying and electrodeposition, have been proposed. However, currently prepared superhydrophobic coatings are highly susceptible to damage because their rough surface morphology is easily damaged by mechanical wear, weak adhesion to the substrate, and poor resistance to harsh conditions, which seriously affects their large-scale application. Therefore, improving the wear resistance of superhydrophobic coatings is an urgent issue. For the micro-nanocomposite structures on superhydrophobic surfaces, the single micron-scale structure protects fragile and functional nanoscale structures because of its ability to withstand more frictional loads than nanoscale structures. Epoxy is a thermosetting resin, and its highly cross-linked three-dimensional network structure endows it with excellent bonding and adhesion performance. The use of sturdy adhesives, such as epoxy resin, to improve the adhesion between the coating and substrate. Moreover, spraying modified micro-nanocomposite particles to create micro-nanostructures is an effective strategy for the large-scale preparation of wear-resistant superhydrophobic coatings. Therefore, in this study, a simple and cost-effective method to prepare a dual-scale durable superhydrophobic coating on an aluminum alloy substrate by one-step spraying of micro / nano mixed particles is proposed. First, an epoxy resin adhesive layer was applied to the surface of the aluminum alloy substrate, after it reached a semi-cured state, a mixed suspension of stearic acid-modified micro SiO₂ and nano TiO₂ particles was sprayed. After curing, the contact angle between the coating and water was ~155.4° and the roll-off angle was ~3°, indicating excellent superhydrophobicity. The prepared coating surface shows an obvious micro-nanostructures, also modified by low-energy substances, which indicates microstructure and composition conditions for constructing superhydrophobic surfaces. The prepared superhydrophobic coating exhibited strong adhesion on substrate, excellent wear resistance and durability, also with good superhydrophobicity under various tests, including 19 times of tape peeling, 20 cm of sandpaper wear, long-term exposure to ultraviolet light, and droplet testing at different pH. The prepared superhydrophobic coating significantly delayed the freezing time of water in extremely cold weather by approximately eight times that of the substrate. Simultaneously, the synergistic anti-corrosion effect of the epoxy resin and superhydrophobic property caused the prepared coating to exhibit excellent anti-corrosion performance in seawater. In addition, the prepared superhydrophobic coating shows excellent self-cleaning performance, and can be used for the photodegradation of pollutants and purification of water because of the photodegradation performance of TiO₂ particles. This simple and environmentally friendly superhydrophobic coating is promised to apply in anti-icing, anti-corrosion and other aspects, and provides a solution for improving the durability of traditional superhydrophobic surfaces.

The effect of substrate-to-target distance on the thickness of carbon/chromium coating uaually occurred when the coating was deposited by a Teer UDP450 unbalanced magnetron sputtering deposition system. The thickness of the coatings was measured by a Teer BC-1 ball crater device. The relation between thickness of coating and substrate-to-target distance was investigated, and the mechanism about the effect of substrate-to-target distance on the thickness of coating was discussed. The results indicated that substrate-to-target distance shows a great effect on the thickness of C/Cr coating, the thickness of coatings is decreased obviously with the increase of substrate-to-target radial distance and has a little change with the increase of substrate-to-target axial distance, the uniformity of thickness of C/Cr coating can be improved gradually when the substrate-placed position is close to central area of working chamber. The dominant factors causing the effect of substrate-to-target distance on the thickness of coating are the

The relationship between remanufacturing engineering and modern Iron & Steel industry was described in this paper. Remanufacturing engineering, with advanced surface technology, design and management methods, made a continuous technical improvement on steel facilities, such as prolonging their life time and retirement period, improving the grade and added value, which was the important method to realize high-efficient and green-steel developing model. The application and development of surface technology, such as electroplating and spraying, on continuous casting mould and roll steel equipment were introduced. It was sure that remanufacturing steel facility products would receive excellent characteristics and good economic and social performance, relying on the surface technology.

Thermal barrier coatings (TBCs) are efficient functional insulation coatings applied to power equipment such as aircraft engines and gas turbines. They have advantages such as low thermal conductivity, good high-temperature phase stability, and fracture toughness. With the continuous enhancement of power systems, key components must often be used in extremely high temperature environments, which can easily lead to the cracking, delamination, degradation, and premature failure of a coating. Therefore, the development of thermal barrier coatings high insulation values and long lives is very important. This article summarizes several typical failure mechanisms of thermal barrier coatings, including failure induced by stress, failure caused by sintering, and failure caused by the infiltration of calcium-magnesium-aluminum silicate (CMAS) and thermally grown oxide (TGO). In order to reduce the residual stress, it is necessary to gradually improve the failure prediction models of TBCs with different preparation processes and different materials, which will improve the reliability and accuracy of the prediction model results. On the other hand, the coating strain tolerance can be increased to release the residual stress, such as by increasing the porosity of the coating and prefabricating cracks in it, which will alleviate the coating stress concentration. In view of the problem of high-temperature sintering, methods to adjust the internal pore structure of the coating by doping metal oxides in the matrix require further study. The thermal-mechanical-chemical coupling effect can be considered to delay the erosion of CMAS, and an in-situ autogenous method can be used to prepare a dense layer, but there have been few studies on this aspect. In addition, a TGO layer with large grain size can be prepared on the surface of the adhesive layer in advance, which can slow down the grain boundary diffusion and limit the growth of TGO by increasing the grain size. Methods have been proposed to reduce the internal porosity of the coating, reduce the difference in interlayer thermal expansion coefficients, and reduce the surface roughness to suppress coating failure. Therefore, the progress on thermal barrier coating research is summarized from two aspects: material selection and the structural design of top coatings. From the perspective of material selection, the problems with using zirconia and some yttrium-stabilized zirconia (YSZ) in long-term high-temperature environments are summarized. In recent years, some advanced coating materials have been developed, including oxide-stabilized zirconia, A₂B₂O₇ oxide, rare-earth tantalite, and self-healing materials. In order to reduce the residual stress, it is necessary to gradually improve the failure prediction models of TBCs with different preparation processes and materials, which will improve the reliability and accuracy of the prediction model results. On the other hand, the coating strain tolerance can be increased to release the residual stress, such as by increasing the porosity of the coating and prefabricating cracks in it, which will alleviate the coating stress concentration. In view of the problem of high-temperature sintering, methods to adjust the internal pore structure of the coating by doping metal oxides in the matrix require further study. The thermal-mechanical-chemical coupling effect can be considered to delay the erosion of CMAS, and an in-situ autogenous method can be used to prepare a dense layer, but there have been few studies on this aspect. In addition, a TGO layer with large grain size can be prepared on the surface of the adhesive layer in advance, which can slow down the grain boundary diffusion and limit the growth of TGO by increasing the grain size. From the perspective of structural design, preparation methods for different coating structures have been introduced. Layered structures, columnar structures, nanostructures, and functionally graded structures are reviewed from the perspectives of their microstructures and corrosion resistance, internal thermal stress, and thermal cycle life values. Finally, the future development directions for long-life thermal barrier coatings are outlined. This review not only discusses the shortcomings of the existing research and direction of future research, but also provides a theoretical basis for the development of a new generation of TBCs with higher corrosion resistances, better thermal insulation values, and longer lives.

Amorphous carbon film, which mainly comprises a network of sp³ and sp² carbon atoms, has been widely used in many fields because of its excellent mechanical and tribological properties, corrosion resistance, chemical inertness, and superb biocompatibility. Amorphous carbon nitride (CN_x) coating has been demonstrated to be a promising lubricating material because of its excellent tribological performance, such as low friction and high wear resistance, during sliding in inert gas environments. However, the deeper mechanism of superlubricity under inert environments remains unclear, which severely limits its industrial application. Previous studies mainly focused on the formation of the sp²-rich carbon tribo-layer on the mating surface and ignored the physical and chemical changes during the sliding process. The high power pulse magnetron sputtering (HiPIMS) technology developed in recent years can effectively improve the ionization rate of the plasma and produce high density, uniform thickness, smooth-surface, and high-adhesion films. Thus, in this study, HiPIMS was used to deposit four kinds of CN_x films. The nitrogen gas flow rates were controlled to deposit different amounts of nitrogen content on the films to obtain CN_x-0, CN_x-50, CN_x-80, CN_x-160, respectively, which allowed exploration of the effect of nitrogen content on the microstructure, mechanical structure and tribological properties of CN_x films. The morphology of the films showed small roughness (Ra ~4.80 nm, CN_x-50, for example) in scanning electron microscopy (SEM) and atomic force microscopy (AFM). In Raman shifts, the sp²-C concentration of CN_x films increased from CN_x-0 to CN_x-80, then suddenly decreased, at a nitrogen gas flow rate of 0.16 L / min. The X-ray photoelectron spectroscopy (XPS) measurements confirmed that the nitrogen concentration gradually increased from 8.99% to 12.37% with the raising of the nitrogen flow rate from 0.05 to 0.16 L / min. In addition to component analysis, the fitted XPS spectra exhibited bond evolution according to different binding energies. The proportion of sp²-C component in the CN_x films increased from 45.99% at 0 L / min to 58.28% at 0.08 L / min and then suddenly decreased to 48.62% at 0.16 L / min, which is consistent with the results of Raman shifts and confirmed by the N1s spectra. In terms of mechanical properties, the nanoindentation test generated a series of complex results. The introduction of nitrogen increased film hardness, and the elastic module first increased from 0 L / min to 0.08 L / min, and then decreased at 0.16 L / min. However, the adhesion of CN_x films decreased at 0.05 L / min and then increased from 0.08 to 0.16 L / min. All the deposited CN_x films had a high degree of graphitization, and they all performed well in the nitrogen gas environment after pre-sliding. Although the effect of the running-in process on friction behavior has not been investigated so far, its effect on reducing wear rates and friction coefficients was verified by our experiments. By introducing 1100 cycles of pre-sliding in relative ambient humidity (RH ~50%), a minimum wear rate (0.60×10^-7 mm³·N^-1·m^-1) was obtained for the CN_x-80 film, and superlubricity (coefficient of friction (COF) < 0.01) was observed for CN_x-50 film for about 40 mins. Optical microscope, focused ion beam high-resolution transmission electron microscopy (FIB-HRTEM), and three-dimensional time-of-flight secondary ion mass spectrometry (3D TOF-SIMS) were used to provide reliable, visual, and direct contact area images of the sliding interface for the analysis of tribological chemistry during the friction test, which showed that the origin of low frictional performance in a nitrogen gas environment is mainly attributed to the termination of the interface by hydrophilic groups such as -OH, -COOH, and -H and the formation of an sp²-rich carbon nitride network tribo-layer on both the mating and top surfaces of the CN_x film. The reconstructed film surface after sliding and the synergy of tribochemical reactions promoted superlubricity. This approach offers a new method for reducing COF and wear of amorphous carbon films and provides a reference for the tribological behavior of carbon nitride films with different nitrogen content.

Conventional nitride coatings cannot satisfy the growing demand for surface protection. In 2004, Ye Junwei broke away from the traditional alloy design concept and creatively proposed a new material design concept for multi-principal element high-entropy alloys. Over the past 20 years, the elements chosen for high-entropy coating research have mostly been transition metals, and it has been difficult to exceed 1 000 HV. Owing to their unique composition and microstructure, high-entropy alloy nitride coatings exhibit excellent mechanical, wear, and corrosion resistance properties, thus providing prospects for the surface protection of industrial components used in harsh environments. Nano-multilayer structures, as an effective means of tailoring the microstructure and properties of conventional hard wear-resistant coatings, have been applied to the design and preparation of these coatings. In this study, self-organized nano-multilayer multi-element AlCrNbSiTiN high-entropy nitride coatings were deposited via cathodic arc ion plating. A self-organized nano-multilayer structure was achieved by optimizing the process parameters to control the spatial distribution of the plasma components. Nano-multilayer AlCrNbSiTiN / CrN coatings and single-layer CrN coatings have also been synthesized via cathodic arc ion plating. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to study the crystals and microstructures of the coatings. A nanoindentation, a friction and wear tester, and an electrochemical workstation were used to investigate the hardness, friction factor, and corrosion behavior of the coatings. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) were used to observe the wear and corrosion morphologies as well as the compositions of the coatings. The results showed that the CrN, AlCrNbSiTiN, and AlCrNbSiTiN / CrN coatings had face-centered cubic structures. The AlCrNbSiTiN coatings had a self-organized multilayer nanostructure with a modulation period of 12 nm, and the AlCrNbSiTiN / CrN coatings had a multilayer nanostructure with a modulation period of 24 nm. The highest hardness of the AlCrNbSiTiN coatings is 34.5 GPa, with H / E and H³ / E² values of 0.076 and 0.166, respectively. The AlCrNbSiTiN / CrN coating had the lowest friction factor of 0.389, whereas those of the CrN and AlCrNbSiTiN coatings were 0.437 and 0.514, respectively. The AlCrNbSiTiN / CrN coatings show the highest corrosion potential of -47 mV, whereas the AlCrNbSiTiN coatings have the lowest corrosion potential of -157 mV. The AlCrNbSiTiN / CrN coatings had the highest critical pitting potential of 900 mV, which was higher than the 690 mV for the CrN coatings and slightly higher than the 883 mV for the AlCrNbSiTiN coatings. The passivation width of the AlCrNbSiTiN coatings was 943 mV, which was higher than the 66 mV of the CrN (645 mV) and AlCrNbSiTiN / CrN coatings. The corrosion current density of the AlCrNbSiTiN coatings was 2.49×10^-8 A / cm², and the passivation current density was 1.41×10^-6 A / cm², which were less than the corrosion current density of the CrN coatings of 3.04×10^-8 A / cm² and passivation current density of 1.32×10^-5 A / cm². This value was also less than the corrosion current density of the AlCrNbSiTiN / CrN coatings of 5.06×10^-8 A / cm² and the passivation current density of 6.67×10^-5 A / cm². The AlCrNbSiTiN coatings exhibited the smallest pitting holes on the surface. Compared with the CrN and AlCrNbSiTiN / CrN nano-multilayer coatings, the self-organized AlCrNbSiTiN nano-multilayer coatings showed the best comprehensive performance with a hardness of 34.5 GPa, friction factor of 0.514, critical pitting potential of 883 mV, passivation width of 943 mV, and corrosion current density of 2.49×10^-8 A / cm². Based on these results, self-organized nano-multilayer high-entropy nitride coatings can be prepared using arc ion plating technology by regulating the spatial distribution of plasma components. Self-organized nano-multilayer high-entropy nitride coatings exhibit superior mechanical, frictional, and corrosion resistance. This study provides a new approach for preparing nano-multilayer multi-element structured coatings.

The rapid development of artificial intelligence technology has led to significant changes and opportunities across various sectors. Machine learning, an important branch of artificial intelligence, can discover laws and patterns from data to make predictions and decisions. Furthermore, it has been widely used in the field of laser cladding in recent years. Laser cladding technology has emerged as a transformative method with numerous advantages, positioning it as a key player in various industrial applications. Its advantages, including high fusion efficiency, optimal material utilization, robust bonding, and extensive design flexibility, render it indispensable for repairing complex surface defects in metal parts. The occurrence of defects during the cladding process can significantly affect the quality and performance of the cladding layer. Ensuring the reliability and repeatability of cladding quality remains a significant challenge in the field of laser cladding technology. In this study, the application of machine learning algorithms in the field of laser cladding defect assessment is explored. A comprehensive and in-depth analysis of common defects and their formation mechanisms in the laser cladding process is provided. The acoustic, optical, and thermal signals generated during the cladding process are summarized, and the corresponding relationships between these signals and the cladding defects are described. Commonly used methods, sensors, and signal characteristics for monitoring the laser cladding process are summarized. Additionally, the classification and features of machine learning algorithms are organized and their use in signal processing is reviewed during the laser cladding process. The classification and characteristics of machine learning algorithms and their applications in laser cladding signal processing are summarized. Machine learning algorithms have been employed in detecting defects in laser cladding, typically by constructing datasets from features extracted from collected signals, the cladding process, and defect characteristics. These algorithms are used to establish relationships between the signals, defects, and the process. However, most current studies on laser cladding monitoring focus on a single pass or a small area of the cladding layer. The use of such small datasets can lead to model overfitting, thereby reducing the accuracy of defect detection. Nevertheless, the application of these algorithms facilitates the introduction of a dynamic feedback control mechanism that optimizes the cladding process and effectively mitigates defects. The convergence of laser cladding and machine learning has emerged as a vibrant area of research, tackling crucial issues and expanding the limits of quality assurance and process optimization. Researchers, both domestically and internationally, have examined pores, cracks, and other defects at various scales through experiments and simulations. However, the mechanisms behind these defects and their impact on the quality of cladding are not yet fully understood. There is a need for more comprehensive methods to study the laser cladding process. Developing a quantitative evaluation system that links the laser cladding process, signal data, and defect quality is a critical challenge in ensuring the reliability of laser cladding quality. Currently, various sensors, including acoustic, optical, and thermal types, are utilized to monitor the laser cladding process. These sensors aid in examining the relationship between the process signals, defects, and quality. However, the limitations in sensor accuracy and the efficiency of defect feature extraction pose challenges in establishing a precise process-signal-defect relationship. The predominant machine learning algorithms used in current research are supervised learning algorithms. However, unsupervised and semi-supervised learning algorithms, which require less data labeling, are drawing attention in the fields of laser melting and cladding process monitoring, demonstrating significant potential. This review emphasizes the current research hotspots and directions for applying machine learning methods in laser cladding.