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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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.

Currently, few studies have addressed three-dimensional numerical models that consider oil film thickness, hydrodynamic pressure, and cavitation effects. Notably, a research gap exists in exploring the influence of texture distribution modes on lubrication performance. Therefore, advancing relevant research is imperative. To investigate the impact of surface texture distribution modes on lubrication performance under fluid lubrication conditions, this study aims to establish a three-dimensional calculation model for non-uniform texture distribution while accounting for oil film thickness. The model will utilize Computational Fluid Dynamics (CFD) methods, along with a User Defined Function (UDF) and dynamic mesh technology, to systematically explore how texture area density and distribution modes affect key parameters, including friction factor, oil film thickness, pressure distribution, and gas phase distribution. The numerical simulation results indicate that, under constant external load conditions, increasing texture area density leads to a decrease in the spacing of uniformly distributed textures. This phenomenon enhances the hydrodynamic lubrication effect while concurrently inhibiting the cavitation effect, resulting in a thinning of the oil film and an increase in the friction factor. In contrast, non-uniformly distributed textures enhance the hydrodynamic lubrication effect and weaken the suppression of the cavitation effect. This leads to an increase in the bearing capacity of the oil film, thickening of the oil film, a decrease in the velocity gradient, a reduction in shear stress, and a lower friction factor. Additionally, non-uniformly distributed textures alter pressure distribution, forming a localized high-pressure zone. The high-pressure zone generated by gradually sparse textures is larger and positioned closer to the symmetry center compared to that created by closely distributed textures. In terms of gas volume, the cavity volume associated for sparser distribution textures is greater than that of more closely arranged textures. Overall, lubrication performance is superior for sparser distribution textures compared to closely arranged ones. When the texture area density is 14.14%, the friction factor for sparser distribution textures is reduced by 26.5% compared to uniformly distributed textures. Simultaneously, the air volume fraction increases by 22.9%, and oil film thickness increases by 53.5%. For closely distributed textures, the friction factor decreases by 24.2%, the air volume fraction increases by 16.7%, and the oil film thickness increases by 32.5%. According to the experimental results, as rotational speed increases, oil film thickness across all three texture distributions demonstrates an upward trend, enhancing lubrication at the friction interface and reducing the friction factor. Notably, the non-uniformly distributed texture exhibits greater oil film thickness and a smaller friction factor than the uniformly distributed texture. This finding suggests that non-uniformly distributed textures can effectively improve lubrication performance. Furthermore, sparser distribution textures outperform closely arranged textures in overall performance, corroborating the simulation results. In this study, a UDF program was employed to control and compute in FLUENT software, considering the influence of changes in oil film thickness under constant load conditions. By analyzing the impact of surface texture distribution modes on lubrication performance, this study provides new insights and theoretical references for optimizing texture distribution design and enhancing research methodologies related to texture performance.

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.

Friction and wear is one of the main failure modes of materials. Reducing friction and wear is significant for indus- trial development and environmental protection. The temperature is one of the major parameters in the friction and wear test, which has a great influence on the process of friction and wear. The influence of temperature on friction and wear performance is described and the mechanism and reason are analyzed. First of all, the temperature will affect the physical and chemical proper- ties of the surface materials, which could affect the surface structure and coating. Secondly, the properties of solid or liquid lu- bricants in the friction pair can be changed with the increase of temperature and the friction and wear properties could be observ- ably influenced, especially on the textured surface. At last, temperature will affect the surface friction and wear properties by changing the wettability of the base surface. The research is important to the selection of materials and lubrication modes of fric- tion pairs working under high temperature, as well as the development of new technologies such as engines and rockets.

The number of criminal cases involving metal objects, such as controlled knives, has gradually increased in recent years. Perpetrators frequently leave fingerprints on metal surfaces, such as stainless-steel door handles, tools, and knives, which can provide crucial evidence. Traditional methods for developing latent fingerprints on metal surfaces include powder, laser, multiband light-source, suspension development, smoke, and high-voltage electrostatic methods. When traditional methods are used to reveal fingerprints on metal surfaces, the ridge lines of the fingerprints often visually interfere with scratches on the metal surface, which can affect the clarity of the fingerprint display. Furthermore, these methods require high equipment standards and are challenging to operate onsite, making them difficult to be implemented widely by local public security organizations. The vacuum metal deposition (VMD) exhibits several characteristics that make it highly sensitive and versatile. One of its key advantages is its ability to preserve DNA and other biologically active components in fingerprints, making it suitable for various applications. VMD is widely used to reveal the latent fingerprints of nonpermeable and semipermeable objects, and it also has a significant effect on aged and problematic latent fingerprints. The handprinted lines are clear and coherent, displaying significant contrast and detailed features. The advantage of VMD lies in its strong sensitivity and effective development of potential fingerprints on challenging materials that conventional methods struggle to process, thus playing a crucial role in critical and complex cases. According to the specifications for producing handprinted samples, latent fingerprints were stamped on brass, red copper, 304 stainless steel, and aluminum alloys. First, this study examined how the combination of two sprayed metals, arranged according to their relative atomic masses, affected the appearance of handprints. Based on this premise, the effects of the quantity and sequence of the sprayed metal on the appearance of the handprints was further investigated. Finally, the effect of the remaining time of latent fingerprints on the development of fingermarks on the four metal objects was examined through statistical analysis. This includes the display rate, average score of the developing effect, and number of latent fingermarks corresponding to the grade score of the development effect. In the experiment, silver and zinc were the highest-quality combinations of metals sprayed on brass, red copper, and 304 stainless steel. For the spraying process, 10 mg of silver and 100 mg of zinc were applied in order of silver followed by zinc, which yielded the best results with latent fingerprints. Gold and zinc were the highest-quality combinations of metals sprayed onto aluminum alloys. For the spraying process, 4 mg of gold and 100 mg of zinc were selected in the sequence of gold followed by zinc; this sequence yielded the best-quality latent fingerprints. Differences in the surface structures of metal objects resulted in varying adsorption capabilities for the different sprayed metals. In addition, the contrast in the color background on different metal substrates caused the combination of zinc / silver to have an optimal effect on brass, purple copper, and 304 stainless steel, whereas the combination of zinc / gold yielded superior quality on aluminum alloy substrates. Moreover, the appearance rate of latent fingerprints on the four types of metal objects gradually increased on days 1, 4, and 7. VMD effectively revealed latent fingerprints on metal objects within a retention period of seven days. In addition, the quantity of sprayed metal, combination of different sprayed metals, sequence of sprayed metals, and remaining time of latent fingerprints influenced the display rate and the developing effect of potential handprints on metal objects. VMD has a significant advantage in developing latent fingerprints on metal objects and serves as a valuable alternative to existing development methods.

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.

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.

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.

Integrated die-casting molds have emerged in response to lightweight, energy-saving, and environmental protection policies in the automotive industry. These molds are subjected to the alternating effects of high-temperature and high-speed aluminum liquid cooling and heating, and traditional surface treatment technologies cannot meet these harsh service conditions. The coating prepared by high-energy pulsed magnetron sputtering (HiPIMS) is dense, smooth, and exhibits good mechanical properties. The preparation of the AlCrN coating using HiPIMS technology is an important measure for improving the aluminum adhesion resistance of integrated die-casting dies. Based on plasma emission spectroscopy (OES), HiPIMS technology was used to prepare high-performance AlCrN coatings with a dense structure at various N2 / Ar flow ratios. The discharge characteristics and time-averaged OES spectra of HiPIMS were examined using a digital oscilloscope, high-voltage probe, current probe, and plasma emission monitor. The crystal phase structure, grain size, and surface cross-sectional morphology of the coating were analyzed using an X-ray diffractometer and scanning electron microscope. The nano-hardness and elastic modulus of the film were measured using a nano-indentation instrument. An anti-adhesion test with liquid aluminum was designed to assess the performance of the coating structure at 700 °C. The results showed that as the N2 / Ar flow ratios increased, the peak current under HiPIMS and peak power density also increased. The deposition rate first increased and then decreased, and the grain size and microstructure of the coating changed significantly. Numerous ionic states appeared in the film-forming environment, and the strength of CrII, AlII, and NII increased significantly. As the strength of CrII / CrI increased, the ionization rate of metal atoms in the target also increased with the N2 / Ar flow ratio during sputtering. With the change in the N2 / Ar flow rate, the coating structure primarily exhibited three states: an amorphous structure, a hcp-AlN and fcc-AlCrN mixed phase, and a single fcc-AlCrN phase. Obvious differences could be observed in the microstructure of each phase. The variation in N2 / Ar flow ratios significantly affected the structure and properties of AlCrN coatings. In the experiment, the nitrogen content of the coating remained high and demonstrated an overall increasing trend with the N2 / Ar flow ratio, ultimately approaching the stoichiometric composition in the fcc-AlCrN structure. The fcc-AlCrN phase coating with a preferred orientation of (220) was prepared at the highest N2 / Ar flow ratio, resulting in the highest hardness and elastic modulus. Simultaneously, it had the highest H / E and H3 / E2 ratios as compared with the other experimental groups. A laboratory-level efficient anti-aluminum adhesion test was next designed. In this test, the structure demonstrated good characteristics without aluminum adhesion, and the phase structure and composition of the coating did not change significantly. The surface integrity of the coating remained intact without obvious damage. The stability of the fcc-AlCrN structure in the liquid aluminum was the key to its excellent anti-aluminum adhesion performance. In this study, high-performance AlCrN coatings were prepared by varying the N2 / Ar flow ratio, which improved the aluminum adhesion resistance of the integrated die-casting die surface.

Ni-based alloys exhibit low density, good plasticity, high strength, and excellent corrosion and wear resistance under high-temperature conditions. Therefore, they are often preferred in high-temperature and harsh environments. They are widely used in various military engines and civil equipment fields such as thermal power generation, petrochemicals, and metallurgical industries. However, they are more prone to fatigue and creep damage in high-temperature environments, which seriously affect the working efficiency, reliability, and durability of equipment utilizing Ni-based alloys. To improve the service life of Ni-based alloys in harsh environments, NiCoCrTaAl-TiC composite powders were prepared via vacuum-mixed ball milling, and metal/ceramic composite coatings were successfully deposited on the surface of K418 nickel-based alloys via laser cladding technology. The phase compositions and microstructures of the coatings were examined using an X-ray diffractometer and metallographic microscope. The effects of different Al contents (0, 5, 10, and 15% ) on the mechanical and tribological properties of the NiCoCrTaAl-TiC composite coatings were examined using a micro-Vickers hardness tester, scanning electron microscope, high-speed reciprocating friction and wear tester, and ultra-depth-of-field microscope. Actual operating environments, such as rainwater environment (pH6.2), seawater immersion (pH8), and lubricating oil were simulated for the coating with the best wear resistance, and the corrosion and wear resistances of the coating in different environments were further examined. The results show that the composite coating is mainly composed of TiC, Cr₂Ni₃, Al₂O₃, and AlNi₃ phases, and intermetallic compounds such as Al₄CrNi₁₅ and Al₄Ni₁₅Ta. The internal structure of the coating is dense and composed of dendrites in the middle and equiaxed grains at the top. As the Al content increases, the average hardness of the coating initially decreases and then increases. The strengthening mechanism of the hardness corresponds mainly to the joint strengthening of TiC, Al₂O₃, and AlNi₃ phases. Under dry friction conditions, with increasing Al content, the wear loss of the coating initially increases and then decreases. Furthermore, the main wear form changes from adhesive to abrasive wear. In summary, when the Al content is 15wt.%, the composite coating exhibits the best microhardness, microstructure, and tribological properties, and its wear resistance is approximately 25% higher than that of the coating with 0wt.% Al content. Subsequently, the 15wt.% Al composite coating was immersed in rainwater and seawater for 2 h, and its friction coefficient was: lubricating oil ＜ rainwater ＜ seawater. The depth of the wear scar and amount of wear were essentially the same as those of the coating without corrosion treatment, indicating that the addition of Al can improve the corrosion resistance of the composite coating.

Cavitation is a phenomenon of material damage under extreme conditions of localized high pressure and heat. It commonly occurs in pumps and other flow-through components and can severely limit the service life of these parts. Polyamideimide (PAI) coatings were originally developed to prevent cavitation erosion damage in steel components. However, because of their lightweight requirements in aerospace, they are now being used as light alloys that can withstand low temperatures. Notably, PAI coatings have high curing temperatures that exceed the withstanding temperatures of most lightweight alloys. Although the addition of epoxy resin (EP) is expected to significantly reduce the curing temperature of PAI, it may also alter its overall properties. The corresponding effect on cavitation erosion performance is currently unknown. To address this issue, we prepared pure PAI coatings (P-280) and EP-modified PAI coatings (P-200 and P-170) with varying PAI contents. Using an ultrasonic vibration-accelerated cavitation erosion test, we then compared the cavitation erosion performances of the samples. Through characterization using X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and nanoindentation, we also analyzed the mechanical and thermal properties of the samples and their force / heat response behaviors under the effects of cavitation load and cavitation heat. This study investigated the mechanical and thermal properties of the samples and their force-and heat-response behaviors using three-dimensional optical shaping. The results indicated that the addition of EP could significantly reduce the curing temperature of PAI by 80–110 ℃. However, this reduction led to the destruction of the mechanical properties of the material, including its toughness, which decreased to 8.21, 5.50, and 3.18 mJ·m^?3 in P-280, P-200, and P-170, respectively. This occurred because of the reduction in rigid molecular chains, such as the imide and benzene rings. In P-280, P-200, P-170, the tensile strength decreased gradually from 114.11 to 75.52 and 70.74 MPa. This reduction in strength led to a decrease in the bearing capacity of the coating and increased fatigue cracking under cavitation load, resulting in the formation of a greater number of larger spalling pits. However, the addition of EP significantly degraded the thermal stability of PAI, making it susceptible to melting and decomposition under cavitation heat. The reductions in temperature corresponding to a 5% weight loss of the P-170, P-200, and P-280 samples after 30 min of cavitation erosion were 15.24%, 14.82%, and 9.05%, respectively. This further accelerated the degradation of the mechanical properties of the coating surface and the damage caused by cavitation erosion. In addition, the heat generated by cavitation erosion promoted pyrolysis and hydrolysis of the molecular chains. XPS results indicated a reduction in the oxygen content after 30 min of cavitation erosion. Specifically, P-280, P-200, and P-170 decreased by 0.67, 1.9, and as much as 3.33at.%, respectively. The breakage of the molecular chains further deteriorated the overall performance of the coatings. The SEM morphology of the P-170 flaking debris showed melting under the heat of cavitation and the subsequent condensation of water into spherical debris particles. After 30 min of accelerated cavitation erosion, the mass losses of P-200 and P-170 were 1.7 and 3.6 mg, respectively. These values were 2.1 and 4.5 times higher than that of P-280, respectively. Considering the curing temperature, overall performance, and cavitation resistance of the coating, P-200 was deemed more suitable for application on the surface of light alloy parts. This study provides guidelines for the research and development of PAI coatings based on its investigation of the relationship between the overall and cavitation performances of PAI coatings under different EP contents.

WO₃-NiO-based electrochromic devices (ECDs), which can actively regulate visible and infrared (IR) light and offer outstanding energy-efficient performance, have been extensively investigated owing to their potential application in smart windows for energy-efficient buildings and light-modulated skylight glass for electric vehicles. However, the high cost and low production efficiency of ECDs severely restrict their large-scale application. Compared with the conventional ECD fabrication process, which involves stacking multiple films on a single glass substrate, the lamination process for assembling a WO₃–NiO ECD by laminating the individual components of glass / TCO / WO₃ and glass / TCO / NiO with a transparent adhesive electrolyte interlayer is gradually becoming mainstream for realizing low-cost, commercially viable, large-area ECDs. However, for the practical production and new application of large-area laminated devices, one must perform a systematic survey from the starting material to device assembly, including high-quality EC oxide targets for large-area sputtering deposition; sputtered EC films with a regulated composition, microstructure, high performance, and color; achieve large transparent adhesive electrolyte foils with high room-temperature ionic conductivity, temperature stability, and high adhesive strength; perform a large-area ECD lamination process in the existing commercialized facilities; realize curved-device fabrication; and achieve an energy-efficient device with neutral color in both tinted and bleached states. Hence, researchers have conducted a series of studies, and the progress is presented in this review. First, the requirements and preparation methods of WO₃ and NiO ceramic targets for large-scale production are presented. An appropriate level of electrical conductivity is required to satisfy middle-frequency sputtering, which is the most commonly used sputtering mode in commercialized films. The EC performance and W / O stoichiometric ratio of a WO₃ film sputtered using a ceramic target can be effectively adjusted by changing the sputtering power and gas pressure under pure Ar atmosphere. In this study, the deposition rate increases from 6.9 to 20.8 nm as the sputtering power increases from 100 to 250 W. Additionally, an 18-nm-thick amorphous tin-zinc-oxide film is used to shield the sputtered WO₃ film so that a room-temperature-deposited film with excellent cyclic stability can be achieved. A high content of niobium (Nb / (Nb+W) = 54.1 at.%) is introduced into the WO₃ matrix to realize a neutral-tinted color and a relatively lower IR absorption in the tinted state. In the NiO film, Li / Si co-doping followed by rapid thermal annealing can enhance the transmittance near the short-wavelength zone in the bleached state, the charge capacity, and the cyclic stability. Additionally, W / Zn co-doping enables a NiO EC film with superior performance to be achieved after tempering at 640 ℃. For the transparent adhesive electrolyte interlayer, a new strategy for significantly improving the ionic conductivity of polyvinyl-butyral (PVB) via a cross-linking reaction with 3-glycidoxypropyltrimethoxysilane (KH560) is established. The cross-linked PVB solid polymer electrolyte (SPE) with 10 wt.% KH560 exhibits a high room-temperature ionic conductivity (1.51 × 10^?4 S·cm^?1 ). Additionally, the prepared PVB-SPE exhibits comprehensive optical, mechanical, and thermal performances, including high visible transmittance (＞ 91%), relatively high adhesive strength (2.13 MPa), and superior thermal stability (up to 150 ℃). The WO₃-NiO ECDs with sizes of 5 cm × 5 cm to 30 cm × 30 cm can be assembled in a commercialized autoclave to realize perfect lamination using the PVB-SPE foil. The device can be operated stably at temperatures ranging from -20 ℃ to 80 ℃, thus underscoring the potential of the PVB-SPE for realizing commercially viable large-area ECDs. Additionally, an ECD is assembled using the WO₃ system with a high Nb doping content. The ECD has a neutral color (a* = 0.6; b* =-2.7) and presents a high energy efficiency in reducing the interior-space air temperature by approximately 4.3 ℃ in its fully tinted state.

Tribocorrosion is a material-degradation phenomenon resulting from interactive effects between wear and corrosion. For various marine equipment, their key metal motion systems are typically affected by the combined effect of mechanical wear and chemical corrosion under the harsh marine environment, which can directly limit their stability and safety. Thus, comprehensive investigations into tribocorrosion behavior is critical for the design of appropriate engineering materials under the marine environment. Advancing marine exploration and deep-sea development necessitates surface and coating techniques to ensure favorable anti-corrosion and anti-wear performances for moving mechanical components. Many conventional techniques have been used to prepare protective coatings, such as spraying, high-energy beam surface modification, and physical vapor deposition (PVD). Among the diverse developed protective coatings, those realized via PVD exhibit favorable properties, including high corrosion resistance and excellent mechanical performance, which can effectively protect precision moving components used in deep-sea or offshore mechanical systems; thus, they are one of the most effective strategies in this field. This article focuses primarily on the development of anti-tribocorrosion coatings achieved via PVD and technologies used in the marine environment, in addition to the main scientific and technical issues encountered in the field. First, the tribocorrosion performance of carbon-based, nitride-based, high-entropy alloy, and transition metal dichalcogenide coatings are introduced, and the role of components and multilayer/nano-multilayer/nanocomposite/gradient structures on their tribocorrosion performance and related failure mechanism are summarized. The multilayer interface in coatings achieved via PVD not only significantly improves their hardness by hindering dislocation movement but also improves their corrosion resistance by hindering the diffusion of H₂O, O₂, Cl^-, and Na⁺ corrosives. To evaluate the tribocorrosion performance of coatings, electrochemical and tribological tests are primarily conducted in early research; currently, tribocorrosion tests are performed using a tribometer equipped with a three-electrode electrochemical system. By adopting in-situ atomic force microscopy (AFM) and an AFM-based “image-wear-image” tribology method, researchers are currently investigating subnanoscale and nanoscale wear, the tribocorrosion phenomenon, as well as the oxide growth mechanism of metallic materials. For advanced synergistic wear-corrosion models, a novel two-dimensional predictive model has been developed for predicting the synergetic wear-corrosion reliability of Ni/GPL and steel. Additionally, a combined experimental and computational investigation has been performed using Al single crystals to develop a crystal-based tribocorrosion modeling framework that considers the effects of lattice reorientation and dislocations on surface corrosion. Additionally, new strategies that combine PVD with other surface-protection technologies have been developed, for example, duplex coating systems formed via the PVD of CrN or carbon-based coatings and thermal layer spraying using a high-velocity oxyfuel. Using these methods, material losses due to the synergistic effects of wear and corrosion can be reduced. In particular, hydrogenated carbon-based coatings present high tribocorrosion resistances under low loads due to their high hardness and excellent corrosion resistance; however, they exhibit catastrophic delamination under heavy loads, whereas hydrogen-free carbon-based coatings exhibit better tribocorrosion performance owing to their gradual shearing characteristic. Additionally, carbon-based coatings can enhance the anti-corrosion properties of microarc oxidation (MAO) coatings on magnesium alloys. The superior low-friction and anti-corrosion properties of carbon-based coatings/MAO render them preferable as protective coatings on magnesium alloys. Cr layers achieved via thermal diffusion metallization and CrN coatings deposited via PVD are used to strengthen the surface of 45 steel, thus improving its surface hardness and abrasion resistance. By implementing ion implantation and Al/AlN/CrAlN/CrN/MoS₂ gradient duplex coatings, both the anti-wear and anti-corrosion properties of AM60 magnesium alloy are improved. For AISI 4140 steel, plasma nitriding applied before the coating significantly improves the corrosion and tribocorrosion resistances of PVD CrN, TiN, and AlTiN coatings. Typical applications of anti-tribocorrosion coatings achieved via PVD include seawater-pump plungers, hydrostatic slipper bearings, ball valves, and components of a helicopter-cockpit instrument panel. Hydrogenated diamonds coated with Cr and WC as transition layers are prepared on the plunger of marine diesel engines. These coatings can significantly improve the hardness and elastic modulus while decreasing the friction factor under heavy-diesel-oil environments. After a bench test is performed, the wear marks on the surface of the plunger with coating are extremely narrow and shallow. For drill pump valves, implementing TiN coatings can increase their service life by three times. In the cockpit of a helicopter, multigradient nano-black coatings achieved via PVD are thin and the thickness tolerance is low; additionally, these coatings satisfy the requirements of the salt spray test. Finally, the development and application of anti-tribocorrosion coatings achieved via PVD under the marine environment are proposed. Machine-learning and big-data sharing services should be used to comprehensively understand the damage mechanism; the optimization and design of the suitable coating should account for the actual operating conditions, such as deep sea, nearshore, and shallow sea; advanced coating equipment should be developed for the inner wall of certain pipelines; and in-situ evaluations and bench experiments should be performed to evaluate the service life of metal mechanical components and coating materials. This review presents a comprehensive and systematic report pertaining to anti-tribocorrosion coatings achieved via PVD for marine applications.

The automotive part, mold, machine tool, medical equipment, and aerospace industries are involved in the cutting of difficult-to-machine materials. The cutting process is subjected to a strong coupling of force and heat, and a hard coating on the surface of the cutting tool can reduce the cutting force and heat generated during the cutting process. With the continuous development of the high-end manufacturing industry in China, cutting tools will be affected by the lack of toughness of the hard coatings, which could lead to premature damage and even catastrophic fractures in the machining processes of critical components. In recent years, inspired by biomaterials, researchers have devoted themselves to overcome the limitations of mechanical properties, such as the hardness and toughness of conventional materials, and endowing them with special functions through the design of gradient structures. Therefore, this paper summarizes several typical gradient hard tool coatings. The current research status and prospects of gradient hard tool coatings are systematically outlined to provide a reference for the development of high-performance tool coatings. First, the properties of hard coatings and their preparation techniques are introduced. Hard coating materials, such as transition metal nitride coatings, are widely used in machining and forming tool industries owing to their excellent properties, including their outstanding hardness, wear resistance, thermal stability, and corrosion resistance. To meet the growing industrial demands, hard coating preparation technologies have evolved from single and conventional coating preparation technologies to diverse composite technologies. Next, the advantages of the gradient hard coatings are analyzed in terms of the gradient design of the elemental composition, deposition parameters, and gradient design of multilayer structures. Gradient structure design can enable the coating to exhibit one or more unique properties and thereby improve the working efficiency and service life of the coated parts. In terms of composition design and structure optimization, the elemental composition gradient structure can effectively solve the problem of sudden changes in the internal properties of the coating and enhance the matching between the coating and the substrate as well as that between the coatings to thereby reduce the internal stress of the coating and inhibit the generation and expansion of cracks. Compared with the elemental composition gradient coating, the multilayer gradient structure can combine the advantages of the multilayer and gradient structures to improve the comprehensive performance of the coating. Moreover, the multilayer gradient structure is easier to realize. Subsequently, the comprehensive performance of the gradient hard coatings was evaluated in terms of microstructure, static performance, and in-service performance. Owing to the wide variety of materials, structures, preparation processes, and technologies used for gradient hard coatings, analyses of the microstructures and properties of gradient coatings can help select appropriate coatings and preparation processes according to specific application scenarios. The static properties mainly include the hardness, bond strength, and thermal stability of the coating, whereas the service properties focus on the wear resistance of the coating, that is, the machining wear of the coating during the actual cutting process. In terms of the performance evaluation of gradient hard tool coatings, the mechanical properties of the coatings are currently primarily analyzed via experimental intuition. Fast and efficient performance evaluations of coatings via experiments combined with simulation calculations or machine learning methods remains a challenge. Finally, the current state of research and future directions for gradient hard coatings are summarized. Computational simulations and data-driven approaches accelerate and simplify material design and discovery processes. Because both material composition and structure affect their properties, in many cases, the structure and composition of gradient coatings and their properties are complex nonlinear relationships that are difficult to represent via experimental experience or theoretical models. In contrast, machine learning can be used to predict the coating properties as well as the design and optimization of gradient structures by constructing models for the interconnections between the composition and structure to inform the design and optimization of gradient structures. This study focuses on the gradient design of hard tool coatings and their performance evaluation to provide a theoretical understanding of the gradient design and performance evaluation of hard tool coatings.

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

采用反应火焰喷涂方法在H13钢表面制备的Mo2FeB2三元硼化物金属陶瓷涂层,分析了涂层的显微组织、显微硬度、耐磨性能及抗热疲劳性能.结果表明,经过火焰喷涂获得Mo2FeB2三元硼化物金属陶瓷涂层,其显微硬度达到1 200 Hv0.1,具有良好的耐磨性能和抗热疲劳性能.

In complex service conditions, 30CrMnSiNi2A—an ultra-high-strength steel widely used in the aerospace and other industries—is highly susceptible to sand and stone impact, which result in a sudden high load applied to the component. Although there are many studies on its reciprocating friction wear behavior, there is a lack of research on its impact on the wear behavior. To address this gap. In this paper, impact wear tests on three specimens, 30CrMnSiNi2A substrate, chrome-plated surface and nickel-plated surface, were carried out with varying numbers on a homemade impact wear equipment in the laboratory. Analyses of the material, wear behavior, and impact dynamics response data were performed using Vickers hardness testing, X-ray diffraction, optical microscopy, 3D profile scanning, scanning electron microscopy, and energy dispersive X-ray spectrometry. The impact wear resistance and wear mechanism of the materials were investigated after different surface treatments. The results show that owing to its high hardness, the chrome-plated specimen surface has the best resistance to impact wear at a low number of impact cycles. The wear volume was reduced by a factor of approximately three compared to that of the substrate, and the depth of the cross-sectional profile of the wear marks was minimized. The nickel-plated surface specimen was the second weakest, and the substrate exhibited the weakest resistance to impact wear at a low number of impact cycles. As the number of cycles increased, impact resistances of the three specimens became similar. This is because the greater the hardness of the chrome-plated specimen, the greater is surface brittleness, and impact process easily produces cracks in the early stage. As impact wear proceeds, debris forms and falls off the surface, increasing wear, which has a significant impact on the impact resistance. As the number of impact cycles increased, work hardening of the substrate and nickel-plated surface specimens became more pronounced, resulting in an increase in the hardness of both specimens. While the nickel-plated and untreated specimens showed a slower decrease in the impact wear resistance, the difference in the wear volumes of the three specimens was very small when the number of cycles reached 5×10⁴. The untreated specimens showed the best wear resistance at this time, with the depth of the wear mark cross-sectional profile and wear volume being minimized. The electron microscopy analysis revealed that the substrate predominantly suffers oxidative wear in the pre-wear stage, while with an increase in the number of cycles, the substrate mainly suffers adhesive wear; abrasive chips are compacted on the specimen surface, which minimizes its wear volume. However, the chrome-plated surface specimen exhibited a sharp increase in wear volume owing to debris flaking. As the number of cycles increased, the increase in the depth of the cross-sectional profile decreased for all three specimens, which was also owing to the increase in adhesive wear. Further, the energy absorption rate of chromium-plated specimens was only approximately 35% in the early stage of impact wear, whereas it was approximately 60% for the substrate and nickel-plated specimens. When the number of cycles reached 5×10⁴, the energy absorption rate of all three specimens was approximately 65%, and the impact wear resistance of the surface of three specimens was similar. The mechanisms of different coatings during impact wear were explored, complementing the exploration of the impact behavior of the material. Currently, impact wear on aerospace components drastically reduces the service life of the material, and in response to this problem, this paper proposes a new engineering solution of chrome plated on the surface of the specimen, which significantly improves the service life of the specimen under low number of impacts wear. In the future, there will be a need to continue to apply surface treatment technologies for high-cycle impact wear order to improve the service life of parts that are subject to frequent impact wear.

The high-speed rub between the rotating and stationary parts of compressors plays a crucial role in the safe operation of aero engines. Extensive research has been reported on high-speed friction issues concerning compressor rotors and stators. Nevertheless, systematic reviews of relevant research progress have been lacking. This issue must be examined from the perspective of high-speed friction wear and energy-dissipation mechanisms so as to ensure the safe design of advanced aero engines. The operating conditions of the compressor rotor–stator systems are characterized by small radial clearances, high relative tangential velocities, high airflow pressures, and elevated temperatures, which inevitably result in radial rubbing. This high-speed rubbing can damage both the stator coatings and rotor blades, and in extreme cases, lead to serious safety incidents such as "titanium fires " in aero engines. This paper presents a systematic review of research findings pertaining to high-speed friction and wear in rotor–stator interactions, focusing on the mechanisms of friction-induced wear and the associated heat generation. On one hand, the high-speed friction between compressor rotors and stators is influenced by various operational parameters such as intrusion rate, sliding velocity, and contact depth. On the other hand, factors inherent to the rubbing surfaces, such as blade thickness, coating hardness, and material thermophysical properties, also play a crucial role in determining the rubbing behaviors and mechanisms. The predominant wear mechanisms include adhesive wear, abrasive wear, oxidative wear, and several wear maps have been established. Among the operational parameters, intrusion rate and rubbing velocity have the greatest influence. In addition to the typical stator coatings, several new coatings for both the rotor and the stator have been proposed, and corresponding friction and wear mechanisms have been investigated under laboratory conditions. Accurate prediction of the increase in temperature is critical for addressing the heat generation during high-speed friction. A major challenge lies in determining the heat flow distribution; in this regard, various calculation methods have been developed based on fundamental assumptions. These methods provide a theoretical basis for estimating the increase in temperature. After determining the heat flow distribution, a thermal–structural coupled model can be established using finite element analysis to calculate the temperature increase. Experimental results can be used to refine the model and improve the calculation reliability. Moreover, molecular dynamic simulation provides a novel approach to calculate friction heat distribution and flash temperature, without requiring the use of the currently used heat partition coefficients. The heat generated during high-speed friction significantly affects the wear behaviors and mechanism, which is the focus of current studies. However, variations in wear mechanisms may also influence the friction heat generation and partition, especially when tribo-films or tribo-layers with distinct thermal properties from those of the original materials are formed on the surface. By controlling the operational conditions and designing friction interfaces, the generation, distribution, and dissipation of frictional heat can be altered and controlled, thereby reducing the friction and wear produced and, most importantly, the probability of titanium fires. Previous research has revealed friction wear mechanisms and the influence of friction heat under the action of multiple factors, providing theoretical guidance and a basis for engine structural design and coating development. Further studies should focus on novel coating–metal material combinations and explore the effects of additional operational conditions, as well as the influence of complex high-temperature, high-pressure, and high-velocity flows. Moreover, the effects of heat–solid–flow coupling and flash temperature on the friction, wear mechanism, and energy dissipation mechanism should also be considered to effectively address complex problems such as titanium fires. This review provides meaningful guidance for frictional heat calculation, comprehensive analysis of the friction and wear mechanisms of the rotor–stator systems, and development of novel coatings.

The status and development background of remanufacturing engineering in cyclic economy were described, the energy conservation profit and environmental protection effect of failed engines were analyzed, and the relationship between remanufacturing engineering and surface engineering was discussed. The results showed that the energy conservation profit and environmental protection effect are the best when the failed engines are overall remanufactured. Remanufacturing 10000 engines, the energy could be saved by 14.5 millions kilowatt-hours and the emission of CO2 could be reduced by 0.6 thousands tons. The application of surface techniques in remanufacturing engineering could improve the utilization rato of old engine parts from 72.3 % to 90 %.

This paper introduced the research and application of double glow plasma discharge technologies, including single- element discharge, multi-element discharge and complex discharge. The results showed that the double glow plasma discharge technology can improve greatly the wear-resistance, corrosion-resistance and anti-oxidation of components and prolong their service life, this technology can play an important role in energy and materials-saving, environment-protection, as well as cost-reducing.

Reducing energy consumption is consistently desirable, with the aim of avoiding aggravation of the global energy crisis. Creatures in nature have adapted to their surroundings as a result of biological evolution. Learning how nature creatures adapts to environmental challenges may help solve many challenges in engineering. Underwater drag reduction is a dominant functional strategy developed by the long-term evolution of high-speed swimming organisms such as fish, revealing the relationship between topography characteristics, material properties, and drag reduction functional mechanisms can provide a feasible reference scheme for solving the problem of high-friction resistance on high-moving surfaces. Based on this strategy, this review takes fish skin as a prototype, the unique structure characteristics of sharkskin and dolphin skin are briefly analyzed, before the topography characteristics and multilayered structure of tuna skin are revealed and summarized. The characterization results show that tuna skin has structural characteristics and mechanical properties that result from imbricated fish scales covered by a flexible epidermis layer and embedding in a flexible dermis layer. This structure could be one reason for tuna swimming faster than sharks and dolphins. As more topographical features of other fish skins have been discovered and characterized, some fish scales have been exhibited excellent drag reduction performance in varying conditions. The unique structure characteristics, material properties, and special function of fish skin can provide a useful source for scientific development, technological invention and creation, and engineering technological problems. Drag reduction surfaces inspired by these unique structures and material properties were fabricated using a variety of processing methods, and are summarized in this review. The drag reduction performance of different bionic surfaces differs due to various shapes which have been constructed on microscale or nanoscale surfaces, size dimensions, and material properties. Even so, the drag reduction mechanism of those bionic surfaces can be roughly divided into three categories. First, the drag reduction effect is brought about by the unique structure and its drag reduction mechanism is summarized as the structure effect. The unique structure has a direct influence on the characteristics of the near-wall flow field, such as the “water trapping” effect of the microcrescent array inspired by Ctenopharyngodon idelluse fish scales that can lower the velocity gradient and generate a fluid-lubrication film to reduce shear wall stress between solid and fluid interface. Second, the compliant mechanism is summarized in which the drag reduction effect is caused by a flexible or compliant surface. Typically, the compliant surface acts as a resilient energy-absorbing coating that can delay the boundary layer transitioning from laminar to turbulent flow. Finally, a composite mechanism type is proposed in which the drag reduction effect is brought by coupling of the flexible coating and the unique structure characteristics. The composite surface with unique structure coupling with functional coating not only has excellent drag reduction performance, but also has other useful functions such as antifouling and noise reduction. Those drag reduction mechanisms evolved in nature can provide new bionic drag reduction systems and provide inspiration for innovation to solve engineering problems. At the end of this review, the application of the bionic surfaces inspired by fish skin is briefly introduced. On this basis, the future development and application of bionic surface drag reduction technologies are prospected. Although has restriction development and application all sorts of factors, but with the continuous development of manufacturing technology and materials, infiltration and emergence of many scientific branches will become a trend in the field of bionic drag reduction. This review can serve as a foundation for an in-depth analysis of the hydrodynamic performance of fish as well as a new inspiration for drag reduction and antifouling.

Bearings, as the core components of mechanical equipment, reduce friction and ensure rotational accuracy. Bearing steels, which are critical materials for the realization of advanced bearings, must have a long service life and high reliability. With the rapid development of the aerospace and military fields, the local temperature of bearings in aircraft engines, high-speed-train bogies, and rapid-fire weapon systems can reach 350 ℃ or higher. This exceeds the upper temperature limit of conventional bearing steels such as GCr15 and M50NiL. Thus, third-generation bearing steel, exemplified by CSS-42L high-alloy steel, which exhibits excellent corrosion resistance and fracture toughness, has been developed in recent years. It is known that friction and wear damage on the surface of bearing steel under rolling contact are the main factors causing failure of bearing components at elevated temperatures.Researchers found that gradient nanograined (GNG) materials can effectively reduce friction and wear damage by preventing surface roughening and the formation of brittle tribo-layers. However, there is limited research on the tribological behavior of GNG CSS-42L bearing steel at elevated temperatures. In this study, GNG CSS-42L bearing steel was fabricated using surface mechanical rolling treatment. The effect of the gradient nanostructure on the tribological properties of CSS-42L bearing steel was investigated. By also analyzing wear morphology and subsurface microstructure evolution, the corresponding friction and wear mechanisms were clarified. The average grain size of the topmost layer of the GNG CSS-42L bearing steel was 25 nm, which gradually increased with the depth from the surface. The grain size at a depth of 100 μm reached 500 nm or more. Notably, the entire GNG layer exhibited a martensitic structure. High-temperature friction tests within the temperature range of 25-500 ℃ were conducted on the coarse-grained (CG) and GNG CSS-42L bearing steels. The factor of friction of CG CSS-42L decreased from 0.64 to 0.43 as the temperature increased to 500 ℃, and the wear rate initially increased to 3.5×10^?5 mm³ / (N·m) at 350 ℃ and then decreased to 6×10^?6 mm³ / (N·m) at 500 ℃. Compared to CG bearing steel, the factor of friction of GNG CSS-42L bearing steel was lower than 0.2 at 25 and 200 ℃, then increased to 0.45 at 500 ℃. The wear rates of GNG CSS-42L at 25 and 200 ℃ were 3.8×10^?6 and 3.66×10^?5 mm³ / (N·m), respectively, much lower than those of CG CSS-42L bearing steel. As the temperature increased to 500 ℃, the wear rates of both CG CSS-42L and GNG CSS-42L bearing steels tended to be comparable. The surface morphology of wear scars showed that the proportion of the oxidation layer in the wear scars increased with the wear temperature. This indicates a transition in the wear mechanism of the GNG CSS-42L bearing steel from abrasive wear to oxidation wear as the temperature increased from 25 to 500 ℃. Subsurface microstructure evolution results demonstrated that the original surface gradient structure remained stable within the range of 25-350 ℃. It is believed that the excellent synergy of strength and ductility, along with the strain accommodation in the GNG layer, suppresses surface roughening and the formation of wear debris, leading to enhanced wear resistance. At 500 ℃, the original gradient structure was fully replaced by a nanograined oxidation layer with a thickness of 3 μm during the wear process. Under friction pair contact, microcracks nucleated and propagated in the oxidation layer, causing the spalling of oxidation debris and increased surface roughness. Thus, the factor of friction and wear rate sharply increased at 500 ℃. These results provide an experimental basis and theoretical foundation for prolonging the service life of bearing components at elevated temperatures.

Owing to their high melting point, strength, and hardness, ceramic coatings have been widely used as wear-resistant, corrosion-resistant, and thermal barrier coatings in fields such as aerospace, nuclear power generation, and weapon equipment. Plasma spraying is a highly promising surface cladding technology and has the advantages of a high heating temperature, high deposition rate, low substrate temperature, wide range of spraying materials, and low investment cost, making it one of the most widely used methods for preparing high-performance ceramic coatings. However, with the rapid development of the modern industry, critical equipment or components operating in extreme environments have higher requirements for the service performance of ceramic coatings. Therefore, improving the density and mechanical properties of plasma-sprayed ceramic coatings has become a popular research topic in this field. In recent decades, researchers worldwide have produced various high-performance dense ceramic coatings using optimized plasma spraying technology. Thus, summarizing the current research progress in this technology is highly significant owing to its large-scale promotion and application. First, the technical characteristics, microstructural features, and main issues of conventional atmospheric plasma spraying (APS) ceramic coatings are introduced from the aspects of the working principle and coating deposition process. Owing to the rapid energy dissipation and severe arc fluctuations associated with conventional APS technology, typical atmospheric plasma-sprayed ceramic coatings contain a large number of unmelted or semi-melted powder particles, as well as rich defect structures, such as large-scale pores and interlaminar cracks. This makes it difficult for the performance of ceramic coatings deposited by the conventional APS process to meet the requirements of industrial applications that require coatings with low porosity and mechanical properties, such as wear-resistant coatings, electrolytes of solid oxide fuel cells, and environmental barrier coatings. Subsequently, the structural design, working principle, and coating performance of eight plasma torch technologies for preparing dense ceramic coatings are systematically reviewed. By optimizing the electrode structure, powder feeding method, plasma jet protection, and heating method of the plasma torch, the operational stability, plasma jet energy output, powder heating, and acceleration efficiency of the plasma torch can be effectively improved. This is beneficial for preparing dense ceramic coatings with low porosity and excellent mechanical properties. Subsequently, the principles, process characteristics, and coating features of three typical high-efficiency plasma spraying processes for preparing dense ceramic coatings are elaborated in detail. By improving the operating pressure, plasma jet length, and powder injection method of the plasma spraying process, three dense ceramic coating plasma spraying processes, namely, very-low-pressure plasma spraying, long laminar plasma spraying, and suspension or solution precursor plasma spraying, are developed. These technologies effectively enhance the energy input and utilization efficiency of the plasma spraying process, significantly improving the heating and acceleration performance of refractory ceramic particles in the plasma jet, and are successfully applied in the preparation of various types of high-performance dense ceramic coatings. Finally, the development status of plasma-sprayed dense ceramic coating technology is summarized, and future development trends are discussed. This paper systematically summarizes the plasma torch technology and plasma spraying process used for preparing dense ceramic coatings, and is expected to provide a reference and guidance for the widespread application of plasma-sprayed dense ceramic coating technology.