The friction and wear of mechanical parts mainly occurs on the surface of the material, and about 80% of the failures of parts are caused by surface wear.Friction and wear increase the loss of material and energy, and reduce the reliability and safety.Using laser cladding technology to prepare a high entropy alloy coating on the surface of the substrate can achieve a good metallurgical combination between the coating and the substrate, so as to achieve the purpose of improving surface wear resistance.The main factors affecting the wear resistance of the high entropy alloy coating are the mechanical and physical properties of the coating material (such as hardness, plasticity and toughness), defects generated during the cladding process (such as surface roughness, pores and cracks), friction conditions (such as high temperature environment and corrosive environment).In this paper, the influencing factors and strengthening mechanism of laser cladding high entropy alloy coatings were reviewed and summarized.First of all, the influence of laser process parameters (such as laser power, laser scanning speed, spot diameter) and post-treatment processes (such as heat treatment and rolling) on the quality and performance of the coating were explained.Secondly, the influence of component element selection, high temperature environment and corrosive environment on the wear resistance of the coating was described.Finally, the problems existing in the preparation of high entropy alloy coatings by laser cladding technology were analyzed, and the future development trends were forecasted, such as developing new materials based on far-equilibrium material design theory, using electric field-magnetic field synergy or laser-ultrasonic vibration composite technology to improve the wear resistance of coatings, etc.

In most cases, friction and wear are not conducive to mechanical equipment. As a large country in machinery manufacturing, reducing friction and wear is of great significance to industrial progress and sustainable development. Ceramic-based composite coating is one of the common systems in industrial applications. It uses ceramic materials as the matrix and dopes with lubricating materials as the second phase. On the one hand, it inherits the excellent high temperature stability and strength of the ceramic phases; on the other hand, it improves the lubricating performance in the common friction environment. Therefore, it is widely used in ships, aerospace, biotechnology and high speed trains, etc., and it has received extensive attention and exploration by researchers. Ceramic-based high-temperature self-lubricating composite coatings were focused on in this paper. First, the basic classification of coatings and solid lubricating materials were explained. Then the present researches progress was reviewed, meanwhile, the influence of process parameters on the performance of ceramic-based high-temperature self-lubricating coatings and improvement methods were focused on. Hence the key factors for improving the surface tribological properties of ceramic-based high-temperature self-lubricating composite coatings were summarized, and the feasibility or research potential of improving the friction reducing and wear-resistant performance was discussed. Finally, the current shortcomings of ceramic-based high-temperature self-lubricating composite coatings were summarized in two points: (1) the phase analysis of composite coatings is still focusing on the phenomenon, and without complete theoretical basis; (2) the methods for improving the structure and tribological properties of composite coatings under different preparation processes are relatively simple. Therefore, the corresponding solutions and possible development orientation were proposed preliminarily: (1) further explore the synergistic mechanisms between the ceramic-based and different lubricating phases, additional components, high temperature environment, and establish the theoretical basis of the system; (2) for the different forming mechanisms of preparation processes, the influence of the synergistic effect of process parameters on the microstructure of the composite coating needed to be focused on, expanding the improvement method of the preparation process.

Thermal barrier coating (TBC) materials are an important method to provide thermal protection and prolong service life for aero-engines and gas turbines. In recent years, various kinds of high-entropy (HE) rare earth oxides have emerged in the exploration of novel thermal barrier coating materials, in order to obtain thermal, mechanical, high temperature phase stability, sintering corrosion resistance and other properties better than single principal rare earth oxides through HE effect on the thermodynamics and kinetics of hysteresis diffusion effect, the structure of the lattice distortion effect and "cocktail" effect on the performance. The thermal, mechanical and other performances of HE rare-earth zirconates, cerates, hafnates, phosphates, tantalates, niobates, etc. were summarized and analyzed in comparison with the performance of the corresponding single phases to investigate the various factors affecting the performance. Finally, it was pointed out that in the future, it may be possible to combine experiments with first-principles calculations to select high-entropy ceramic thermal barrier coating materials with superior comprehensive performance; at the same time, extending high-entropy to complex components or medium-entropy ceramic thermal barrier coating materials is also an important development direction.

FeCoCrNiAl_x (x=0, 0.5, 1.0, mole ratio, the same below) coatings were prepared on the surface of TC4 titanium alloy by electric explosion spraying technology. The effects of Al content on the phase structure, surface morphology, microhardness and wear resistance of high-entropy alloy coatings were studied by means of XRD, SEM, EDS, microhardness tester and friction and wear test. The results show that the grain size of the coatings is nano-scale, and simple FCC, BCC and FCC+BCC solid solutions are formed. With the increase of Al element, the phase structure is gradually changed from FCC phase to BCC phase. The surface of the coatings is smooth and dense, without obvious cracks, and the elements are evenly distributed on the surface of the coatings, and no obvious segregation of elements is found. The scratch test shows that the average critical load for the failure of the FeCoCrNiAl_1.0 coatings is 37.2 N. The coating is metallurgically bonded to the substrate. The hardness and wear resistance of the coatings are positively correlated with the Al content. When x is 1.0, the average microhardness reaches the maximum value of 531.8HV, which is about 1.62 times that of the substrate. The FeCoCrNiAl_1.0 coatings have the smallest amount of wear, and the wear resistance is about 3.9 times that of the substrate. The wear mechanism is mainly abrasive wear.

C_f/SiC composites are considered as one of the most important candidates for aerospace thermal protection systems because of their low density, high specific strength, good thermal shock, oxidation and ablation resistance, and excellent high temperature strength retention. However, C_f/SiC composites are prone to oxidize at a temperature above 500 ℃ due to inevitable fabrication defects. So it is necessary to carry out effective oxidation protection for the composites. Oxidation resistant coating is an efficient technology to realize long-term oxidation protection. Based on harsh requirement of thermal protection systems, the research progress of anti-oxidation coatings for C_f/SiC composites was summarized, mainly focusing on the coating material systems and their preparation technologies. Improving the service temperature (≥1800 ℃) and bonding strength of the coatings is an important issue to be solved at present.The preparation of multi-functional coating with longer service time and higher service temperature, as well as oxidation resistance, water vapor corrosion resistance and even good heat insulation performance is an important direction for future development.

The TiC-reinforced Ti-based coating was prepared in-situ on the surface of the titanium alloy TA15 by laser cladding technology. The forming quality, microstructure, phase composition, hardness, and tribological properties were investigated by optical microscope, X-ray diffractometer, scanning electron microscope, energy spectrum analyzer, microhardness tester and friction and wear apparatus. The results show that the coating mainly composes of β-Ti, Co₃Ti, CrTi₄ and TiC, and the good metallurgical bond is formed between coating and the substrate. The microstructure of the coating bond zone is planar crystal and columnar crystal, the middle is dendritic, and the top is equiaxed. Significant differences in the morphology of TiC are observed in each micro-area of the coating. TiC of the top and middle areas is thick dendritic and petal-like, while TiC of the bonding area is needle-like and spherical. The maximum microhardness of the coating is 715HV, which is about 2.1 times than that of TA15 (330HV). Under the same conditions, the wear loss of coating is 30.14 mg, which is about 30.7% of TA15(98.11 mg). The wear mechanism of the cladding coating and substrate is a composite wear mode of adhesive wear and abrasive wear, but the wear degree of the coating is lighter.

High-entropy alloy coatings show great potential for improving the wear resistance of the stainless steel substrate. To investigate the effects of Cu/Si doping on the microstructure and high temperature tribological properties of FeCoCrNi high-entropy alloy coating, FeCoCrNiCu_x and FeCoCrNiSi_x series of high-entropy alloy coatings were prepared on the 304 stainless steel by laser cladding.The microstructure and phase distribution of the coatings were characterized by XRD, SEM and EDS, and the high temperature tribological properties of the coatings were tested by a high temperature friction and wear tester. The results show that both FeCoCrNiCu_x and FeCoCrNiSi_x high entropy alloy coatings form a single FCC-type solid solution with good metallurgical bonding to the substrate under suitable laser cladding parameters.The addition of Cu reduces the surface hardness of FeCoCrNi coatings, but improves the metallurgical bonding due to the increase of thermal conductivity of the coating; the addition of Si promotes grain refinement and improves the surface hardness of the coating. At 600 ℃, the addition of Cu/Si elements significantly improves the tribological properties of the coating, with the coefficients of friction of 0.24 and 0.19 for FeCoCrNiCu and FeCoCrNiSi coatings, respectively, and the wear rates are 1.58×10^-4 mm³·N^-1·m^-1 and 6.77×10^-5 mm³·N^-1·m^-1, respectively, which are 56.1% and 81.9% lower than FeCoCrNi coating.The main wear mechanisms of FeCoCrNiCu coating are oxidation wear, fatigue wear and slightly abrasive wear, while FeCoCrNiSi coating is oxidation wear.

SiC fiber is one of the common reinforcements for ceramic matrix composite (CMC) due to its superior characteristics such as low density, high tensile strength, excellent high temperature resistance and oxidation resistance. The preparation of coating on the surface of SiC fiber can not only improve the mechanical properties, high temperature resistance, oxidation resistance and electromagnetic functional properties of the fiber itself, but also effectively improve the bonding properties of the interface between the fiber and the matrix to promote the fracture toughness and mechanical properties of the composite. The preparation methods of surface coatings on SiC fiber were firstly reviewed in this paper by elaborating on the basic processes and related research progress of etching, deposition, chemical vapor infiltration, and precursor derived methods, and the advantages and disadvantages of different preparation methods were compared. Then the effects of coatings on SiC fibers and their reinforced composite materials were reviewed. Finally, the development trend of surface coating on SiC fibers was briefly summarized. The combination of experimental research and computational simulation can be used to simulate the real service environment of SiC fibers coatings, and the performance of fibers under extreme service conditions can be improved by preparing thermal barrier composite coatings.

Implant infection is one of the most common and serious complications in orthopedics, and it is also an important reason for the failure of implant surgery. When bacteria form a biofilm on the implant surface, it is extremely difficult to be eliminated and attracts more bacteria and fungi. A large number of studies have shown that the use of surface modification technology can effectively reduce the adhesion and accumulation of pathogenic bacteria, thereby preventing peri-implant infection. The formation process of bacterial biofilm on the surface of orthopedic implants and the antibacterial mechanism of metal antibacterial agents were first analyzed. Then, some of the most widely used metal-based inorganic antibacterial coatings at home and abroad and their related preparation processes were reviewed, the problems and improvement methods in the application of these coatings were also discussed, and the development direction of inorganic antibacterial coatings in the future was prospected, such as synergistic antibacterial coatings and bone-promoting antibacterial coatings.

The composite nanocontainer of corrosion inhibitor (MSN-QB) was prepared by loading octahydroxyquinoline (8-HQ) and benzotriazole (BTA) on mesoporous silica nanoparticles(MSN) simultaneously using vacuum adsorption and layer-by-layer self-assembly technology, and added to the epoxy coating to obtain a new coating (MQB). SEM, TEM, FT-IR, Zeta-potential and TGA were used to study the structure changes of the nanocontainer before and after loading corrosion inhibitors and the stimulus response release behavior of the corrosion inhibitors, and electrochemical test and salt spray test were used to study the improvement of coating protection performance by layer-by-layer self-assembly technique. The results show that the loadings of 8-HQ and BTA in MSN-QB are 6.8%(mass fraction) and 7.1%, respectively. MSN-QB has pH response characteristics. The release of 8-HQ and BTA are both inhibited under neutral conditions, but can be released under alkaline (pH=10) and acidic (pH=4) conditions. The release rate under alkaline conditions is higher. MQB coating has the best corrosion resistance. After immersed in 3.5%NaCl solution 20 d, the MQB coating has the largest|Z|_{0.01 Hz} value(2.0×10⁹ Ω·cm²), more than twice that of MQ+MB coating.

With the development of modern science and technology, the demand for survivability of high-speed aircraft is constantly increasing. Its nose cone, wing, tail nozzle and other high-temperature components are easily exposed. In order to hide the high temperature parts of high-speed aircraft, the high temperature application of wave absorbing materials has attracted the attention of researchers. High temperature absorbing ceramic materials can realize the application in the above background. In order to provide the basis for analyzing and improving the problems of limited high temperature degree and narrow absorption bandwidth of ceramic absorbing materials, the absorbing mechanism of ceramic absorbing materials with high temperature resistance was described with the influence of temperature. The high temperature absorbing ceramic materials and coatings can be classified into carbide ceramics, nitride ceramics, oxide ceramics and polymer conversion ceramics. Based on this classification, the electromagnetic wave loss mechanism of ceramic absorbing materials and coatings, and their absorbing properties under high temperature conditions were summarized in this paper.In addition, it is pointed out that the future high temperature absorbing ceramic materials should improve the existing materials' low high temperature resistance and narrow effective absorption band width so as to strengthen its service ability.

Using BSAS powder prepared by solid-state sintering method, Si/Mullite+BSAS/BSAS three-layer environmental barrier coatings were fabricated on SiC substrate by atmospheric plasma spraying process. The phase composition and microstructure evolution behaviour of the environmental barrier coating subjected to various heat treatment temperatures were studied by scanning electron microscope, energy dispersive spectrometer and X-ray diffraction analyzer, etc. The results indicate that as-sprayed BSAS coating is mainly composed of monoclinic BAS phase and amorphous phase; After heat treatment at 1100 ℃, the amorphous phase inside the coating is transformed to hexagonal BAS phase. With the temperature increases to 1200 ℃, the hexagonal BAS phase gradually changes to the monoclinic BAS phase. The fraction of the monoclinic BAS phase reaches the maximum at 1300 ℃ heat-treated; With further increase of the heat treatment temperature, tridymite SiO₂, Ba₃SiO₅ and paracelsian BAS phase appear. Moreover, silicon droplets exude is detected during heat treatment at 1400 ℃.

Infection after surgery is one of the common and most challenging clinical problems, and the development of new antibacterial coating is an effective strategy to solve this problem, which has important scientific and social significance. A bioactive coating with antibacterial function was prepared on the surface of a 3D printed porous titanium bone scaffold. It is discovered that silver (Ag) exists in the coating as a simple substance. As the Ag content increases (0%, 0.5%, 1%, 1.5%, mole fraction), the specific surface area of the mesoporous coating is decreased from 377.6 m²/g to 363.35 m²/g. In vitro mineralization results show that with the increase of Ag content, the apatite inducing ability is decreased slightly. At the same time, the antibacterial test demonstrates that the addition of silver markedly enhances the antibacterial performance of the scaffolds. Adding a small amount of silver (0.5%) can achieve 100% antibacterial rate. The MC3T3-E1 cells are cultured with the scaffolds for 1, 3 and 7 days, and it is found that the Ag-doped MBG coatings have good cyto-compatibility, and the addition of a small amount of silver can promote the proliferation of MC3T3-E1 cells. A simple dipping and pulling method was used to apply the Ag-doped MBG coating to the complex 3D printed titanium scaffolds with complex topological structure. The mineralization performance, bactericidal performance and cellular compatibility of the scaffold are significantly improved, providing a new idea for the further development of multifunctional bone implant scaffold.

Fe-based amorphous alloy coatings have emerged as a key area of research in the field of surface engineering due to its high strength， hardness， and exceptional wear and corrosion resistance. This paper provides a comprehensive review of the preparation， performance， and application status of Fe-based amorphous alloy coatings. It also summarizes the fundamental principles of amorphous alloy material design and typical Fe-based amorphous alloy coatings material systems. The focus is on three coating preparation technologies： thermal spraying， cold spraying， and laser cladding. Additionally， it compiles the research progress made in understanding the tribological properties and corrosion resistance of Fe-based amorphous alloy coatings. Furthermore， it briefly outlines the applications of these coatings in military， medical， industrial fields etc. Finally， it is pointed out that in-depth study of amorphous formation， the establishment of specialized material systems while matching the working environment， and the adoption of post-processing or more efficient preparation methods are the development trends for future research work in this field.

As the turbine inlet temperature in aero-engines continues to rise， conventional thermal barrier coatings （TBCs） are becoming increasingly ineffective at blocking thermal radiation in the near-infrared wavelength range generated by high-temperature gases. The heat transfer of heat radiation can penetrate through the coating and directly heat the underlying metal substrate， thereby compromising the service life of hot-end components. In this paper， the authors’ experimental results are used to review recent developments in the design of novel TBCs materials and structures that combine thermal insulation with enhanced radiation suppression capabilities. A comparative analysis of the near-infrared optical properties of conventional TBCs is presented. The current methods aimed at improving the ability of coatings to mitigate radiative heat transfer are discussed. Particular attention is given to the issue of conventional YSZ-based inability of TBCs to effectively block infrared radiation in the shortwave infrared region. An analysis is conducted on the two fundamental approaches for reducing the infrared transmittance of TBCs， namely， improving the infrared reflectance or infrared absorptance of coatings. Additionally， a systematic summary of the strategies for tuning the infrared reflectance and absorptance of coatings， including influencing factors， underlying mechanisms， advantages， and limitations， is provided. Finally， future trends and breakthrough directions in the development of novel radiation-suppressing coatings， particularly in terms of material and structural design as well as the use of high-performance computational tools， are highlighted.

To produce the porous coating on the inner wall of the pipe is an effective way to enhance heat transfer performance and improve heat exchange efficiency. The electric explosion spraying method was employed to produce the porous coating on the inner wall of the pipe. The surface morphology, roughness and pore distribution of the coating under different initial voltages were studied. The mechanism for the formation of the coating was investigated by the deposition energy and explosive products explained. The results indicate that the initial voltage of the electric explosion spraying influences the microstructure of coating. The optimal porous coating can be obtained when the initial voltage of the electric explosion spraying is 14.0 kV. The optimal porous coating is formed by the accumulation of the small particles. Moreover, the optimal porous coating is obtained, the surface area is 4.47 times that of the uncoated pipe and the porosity of the ideal coating is 57.8%. The uniform round porous coating is formed, when the initial voltage of the electric explosion spraying is 15.2 kV. The porosity of those coating is 40.3%. The formation of the coating depends on the energy deposited on the copper wire during the explosion. The energy deposited on the copper wire acts as the thermodynamic condition for the sprayed particles, determines the energy and particle size of the sprayed particles and the states of the sprayed particles collide with the surface of the base tube or the particles accumulate or form a molten pool. Finally, it influences the microscopic morphology of the coating.

The traditional preparation process of superhydrophobic surfaces(SHS) is complicated and the mechanical stability of SHS is less than satisfactory in most cases, which seriously restricts the practical application. The "binder+nanoparticles" strategy was used to prepare a nonfluorinated, durable and stable superhydrophobic epoxy composite coating on magnesium alloy. The contact angle test results show that the maximum contact angle of the composite coating is 160.2°, and the contact angle is still as high as 103° even after 30 days of soaking in 3.5%(mass fraction) NaCl solution; EIS results indicate that the |Z|_{0.01 Hz} of the composite coating is still above 10⁹ Ω·cm² even after five accelerated aging cycles, demonstrating excellent resistance to salt fog and anticorrosion performance; Friction and wear test results reveal that the |Z|_{0.01 Hz} of the composite coating is as high as 1.84×10⁹ Ω·cm² after mechanical friction under 19.6 N load for 8 h. Due to the excellent blocking barrier of "air cushion", the composite coating can provide efficient and durable corrosion protection for magnesium alloy and the "adhesive+nanoparticles" strategy provides a new direction for the preparation of superhydrophobic coating.

The TiAlN-based coatings have good mechanical and anti-oxidation properties. Therefore, they have been widely used in the surface protection of typical mechanical parts, such as aero-engine compressor blades, cutting tools and precision molds. However, with the continuous improvement of the performance requirements of mechanical parts, the service conditions of the coating are becoming more and more harsh, and the reliability and service life of the protective coating are facing more severe challenges. Addition of the pre-transitional elements into TiAlN coatings is an effective method to improve their properties in various aspects for a prolonged service life. In this work, based on the ternary TiAlN coating, the effects of the addition of pre-transitional elements X (X=V, Cr, Y, Zr, Nb, Mo, Hf, Ta and W) on the structures and properties of TiAlN coatings were systematically discussed with the aid of phase diagrams. Furthermore, the composition-structure-property relationship of TiAlXN coatings was tentatively established. In view of the problems faced by adding pre-transitional elements to TiAlN coating, such as lack of phase diagram calculation assistance, failure behavior of quaternary coating in extreme environment and high cost of coating preparation equipment, the prospects of developing quaternary phase diagram of TiAlXN system combined with phase field simulation, developing TiAlN based high entropy coating and vigorously developing coating preparation technology combined with the advantages of vapor deposition technology were put forward in this paper.

BN and BN/SiC coatings were deposited on the surface of two typical domestic SiC fibers by CVI process, and the composition of coatings was analyzed. The tensile strength of monofilaments was evaluated by Weibull distribution, and the tensile fracture failure behaviors of the fiber before and after depositing coatings were studied. The results show that the carbon-rich layer with appropriate thickness (15 nm) can heal the defects on the surface of SiC fiber and reduce the possibility of fiber failure from the surface. The thickness of the coating prepared by the CVI process is uniform and the composition is stable. After depositing BN and BN/SiC coatings, the tensile strength and elastic modulus of the two kinds of SiC fibers are decreased. BN coatings can also repair the surface defects of the fiber, so that the fiber strength distribution tends to be concentrated. Different from the uncoated fibers, the tensile fracture failure sources of coated fibers are the surface defects of BN and SiC coatings, respectively.

AlCrNiFeTi high-entropy alloy (HEA) with a diameter of 7 mm was prepared as electrode by vacuum arc melting method, and AlCrNiFeTi high-entropy alloy coating was successfully prepared on the surface of 304 stainless steel by using electric spark deposition technology. The microstructure and friction and wear properties of the coatings were studied by XRD, OM, EDS, SEM, microhardness tester and friction and wear tester. The results show that both the AlCrNiFeTi electrode and the coating are dominated by BCC1 and BCC2 simple solid solutions, and the microstructure of the electrode is typical of dendrites. The coating is formed by stacking and spreading of deposition points, and the surface is uniform and dense as orange peel, convex and concave, unfolding for sputtering pattern, and there is no macroscopic defects in the coating cross-section structure, and the thickness is about 59.67 μm.The maximal microhardness of AlCrNiFeTi coating is 587.3HV_0.2, which is about 2.45 times higher than that of the base material. As the load increases, the wear mechanism of the coating changes from oxidized wear and slight abrasive wear to abrasive and adhesive wear. When the friction load is 5 N, the wear rate is 1.213×10^-3 mm³/(N·m), and the friction coefficient is only 0.446. The wear rate of the coating decreases by about 28.3% compared with that of the substrate.

The BN coating was deposited on the surface of typical domestic SiC fibers by chemical vapor permeation (CVI) process, and the fibers were oxidized at 800-1200 ℃ for 1 h. The morphology, structure and composition of BN coated SiC fibers after oxidation were characterized. The property changes of BN coated SiC fibers after oxidation were evaluated by tensile strength of monofilament. The results show that when the oxidation temperature is lower than 1000 ℃, the BN coating and its oxide can effectively prevent the erosion of the inner SiC fibers by O₂, and when the temperature continues to rise, the SiC fibers are oxidized. With the increase of oxidation temperature, the surface oxide of BN coated SiC fibers goes through the process of α-B₂O₃→SiC_xO_y→amorphous SiO₂. The tensile strength of BN coated SiC fibers decreases with the increase of oxidation temperature. Direct exposure of BN coating to oxidizing environments reduces the oxidation resistance of SiC fibers. The failure source of fiber fracture first transitions from BN coating defects to B₂O₃ oxide layer defects and finally evolves into SiO₂ oxide layer porosity defects.

SiC-based ceramic matrix composites (SiC-CMC) are an ideal material for aeroengines with high thrust/mass ratio.In order to prevent the corrosion of SiC-CMC by gas (rich in H₂O and O₂) in the engine, it is necessary to prepare environmental barrier coatings (EBCs) with excellent water and oxygen corrosion resistance, gas erosion resistance and thermal shock resistance. Among many factors that evaluate the performance of EBCs, the bonding strength between EBCs and SiC-CMC matrix is an important indicator, but the limit value of the bonding strength has not been clearly explored.In this paper, main factors to control the bonding strength were studied in order to reach the highest value, including the SiC-CMC matrix state, the tensile strength limit of single crystal Si, and the preparation process of the Si bonding layer, etc. In the SiC-CMC/EBCs system, the interface between the SiC fiber cloth is the weakest part of the bonding strength, followed by the Si bonding layer. The bonding strength limit is 15 MPa, which is the tensile strength limit of single crystal Si in the [400] crystal direction. The bonding strength of the Si layer using atmospheric plasma spraying (APS) or high velocity oxygen-fuel(HVOF) is similar, which is lower than that of mullite or Yb₂Si₂O₇ layer sprayed by the same process.

In order to study and expand the application of Inconel718 alloy in high temperature environment, Co/TiN composite coating was prepared on its surface by laser cladding. Meanwhile, the tribological behavior of the coatings at room temperature (RT) and 600 ℃, and the oxidation resistance at 800 ℃ were investigated by XRD, SEM and EDS analysis, etc. The results show that the hardness of the composite coatings is 1.3-1.4 times higher than that of the substrate. The tribological properties of the coating are tested. When the TiN content is 4%(mass fraction, the same below), the anti-friction properties of the coating are the best. When 6%TiN added, the wear resistance of the coating is the best, and the wear rate can be reduced by 90.02%. In addition, the oxidation experiment shows that the Co/TiN composite coating has a certain oxidation resistance, and the oxidation rate is 8.7634 mg²·cm^-4·h^-1, which is not much different from the substrate.It shows that the composite coating can significantly reduce the wear rate at high temperature while retaining the oxidation resistance of the substrate, and the wear rate decreases with the increase of TiN. The wear mechanism analysis shows that the oxidation wear occurs on all coatings at 600 ℃, and the oxide film on the surface of the coatings also can reduces the wear rate at some extent.

With the continuous development of the aerospace field, the service conditions of high temperature structural components such as metal and carbon materials are increasingly harsh. The service life of high temperature structural components can be effectively improved by preparing silicon-based ceramic coatings on the surface of high temperature structural components and giving them special properties through appropriate processes. In recent years, the polymer precursors conversion ceramic coating has gradually become a novel method for preparing inorganic coatings. The new approach has the advantage of excellent processability and functional scalability, which gets more and more attention from researchers. The research progress of high temperature resistant ceramic coatings based on silicon-containing polymeric precursors was reviewed in this paper. Firstly, the preparation of ceramic coatings from the polymers was introduced, including the influences of silicon-based polymer precursors, fillers, coating and pyrolysis process on the structure and properties of the obtained coatings. Then, the applications of polymer-derived ceramic coatings in high temperature protection fields, such as anti-oxidation, environmental barrier and thermal barrier coatings were discussed. Finally, The problems in improving coating performance and defect control of polymer ceramic coatings were pointed out, and the development direction of polymer ceramic coatings was prospected, for example, by introducing ultra-high temperature elements such as Hf, Zr, Ta into silicon-based precursors, improving the temperature resistance level of ceramic coatings, and developing new efficient ceramic technology to improve the existing efficiency and applicability.

Ceramic matrix composites are desirable materials for the hot end components of high performance generation aeroengines due to their high temperature resistance, low density and excellent high temperature mechanical properties. However, when exposed to combustion environment, the ceramic matrix composites are subjected to serious water vapor corrosion. Thus, environmental barrier coatings are indispensable to apply to their surfaces to extend their service life.The rare earth silicate has become the primary candidate material for the new generation of environmental barrier coating materials because of its suitable thermal expansion coefficient with the substrate, outstanding water vapor corrosion resistance and high temperature stability. The characteristics, preparation techniques and typical service performance of rare earth silicates were reviewed in this paper, with focus on their classification, thermal/physical properties, as well as the damage and failure mechanisms during high-temperature corrosion processes. Finally, the research directions of high entropy design of multi-component rare-earth silicates and the design of new thermal/environmental barrier coating systems were proposed. This paper aims to provide useful references for the further application of rare earth silicate materials.

The electron beam-physical vapor deposition （EB-PVD） technology was employed to fabricate yttria-stabilized zirconia （YSZ） thermal barrier coatings at different electron beam currents （1.2，1.8，2.4 A）. The phase structure and microstructural morphology of YSZ coatings at different electron beam currents were analyzed and characterized. The thermal barrier coatings were also subjected to a 1150 ℃ thermal cycling life test. The failure behaviors of coatings were analyzed by the evolution of the microstructure. The results show that YSZ coatings at different electron beam currents all possess a non-equilibrium tetragonal phase structure. As the electron beam current increases， the columnar grain tip structure of the coating evolves from a triangular shape to a pyramidal shape and then to a ridge-like shape， with the column structure changing from a slender structure to a coarse structure， the dendrites decreasing， and the arrangement becoming more orderly. The thermal conductivity is lower slightly due to the appearance of ordered nanopores in the column of YSZ coatings. The YSZ coating prepared at 1.8 A demonstrates the most excellent thermal shock life of 895 cycles， approximately twice that of the YSZ coating prepared at 1.2 A and 1.3 times that of the YSZ coating prepared at 2.4 A. The slender columnar grain structure prepared at a low electron beam current is prone to sintering failure， while the coarse columnar grain structure prepared at a high electron beam current is prone to thermally grown oxide （TGO） layer stress accumulation failure. The columnar grain structure prepared at 1.8 A could balance the two types of failure behaviors， effectively extending the thermal cycling life of the YSZ thermal barrier coating.

To improve the corrosion resistance of 304 stainless steel, boron nitride nanoplatelet (BNNP) reinforced chemically bonded ceramic coatings with lateral sizes of 3 μm and 300 nm were prepared on the substrate surface by the slurry method. The surface hydrophobic properties of BNNP coatings with different lateral sizes were characterized by SEM and optical contact angle measurement. The corrosion behavior of the coatings under simulated seawater solution was revealed by an electrochemical workstation. The effects of BNNP lateral size and content on the coatings' microscopic morphology and corrosion protection properties and their mechanisms were investigated. The results show that the surface wetting angle of the coatings increases with the addition of BNNP, the coatings of both lateral sizes have excellent hydrophobicity at 1.0%(mass fraction, the same below) BNNP, and the coatings with 300 nm BNNP have significant improvement, which increase the surface wetting angle of the coatings from 38° to 96.972°. The addition of BNNP improves the coating quality, fills the pores and cracks inside the coatings, and BNNP has good hydrophobicity, which actively contributes to the improvement of the hydrophobicity of the coatings. And 300 nm BNNP has a better sealing effect, creating more nuclei and filling the voids between alumina particles and the adhesive. The coatings with the addition of 300 nm BNNP at 1.0% have the highest low-frequency impedance and corrosion potential of 22500 Ω·cm² and 0.344 V, respectively, and the corrosion current density reaches the lowest value of 1.12×10^-7 A/cm². The coatings prepared on the surface of the substrate create a physical barrier that effectively hinders the intrusion of corrosive media into the substrate. Compared with the original coatings, the surface morphology of the coatings with BNNP is denser after corrosion, reducing the defects such as pores and cracks in the coatings. BNNP is chemically stable and has good corrosion resistance, which can further delay and retart the corrosion reaction in the coatings and prevent the contact of the substrate with the corrosive medium. The addition of 300 nm BNNP has smaller lateral sizes and a wider distribution range, thus better impeding the expansion of corrosion paths. There are fewer defects such as corrosion pits and holes on the surface. Therefore, the coatings with the addition of 300 nm BNNP have a better effect on hindering the expansion of corrosion paths.

With the rapid development of China’s manufacturing industry and the emergence of difficult-to-machine materials， there is an urgent need for cutting technology to continuously update and iterate， and the development of cutting tools has become a key factor in improving processing efficiency. In recent years， coating technology has become an effective way to improve the cutting performance of cutting tools. In particular， TiAlN coating has been widely used in cutting tools due to its good wear resistance and stability. However， the traditional TiAlN coated tools have made it difficult to bear the harsh conditions of thermo-mechanically-chemo multiple coupling. How to form solid solution strengthening and fine grain strengthening by element doping， for improving the cutting performance of TiAlN coated tools conveniently and efficiently， has become a research hotspot in this field. Given this problem， the action mechanism and preparation method of TiAlN coating were summarized， the microstructure and phase structure of the coatings obtained by different methods were analyzed， the limitations of TiAlN coating due to oxidation and phase transformation in high temperature were described， and the effects of doping Si， C， Cr， B and V elements on the microstructure， hardness， wear resistance， oxidation resistance and tool life of TiAlN coating were reviewed. Finally， the future development of TiAlN coated tools is summarized.

The continuous casting mould is the most crucial core component of the continuous casting production line，which undertakes the important tasks of cooling，heat conduction，abrasion resistance and high-precision forming of the billet surface during the high-speed vibration drawing process of the molten steel. Based on the engineering application practice of mould surface protective coatings in domestic steel plants， the advantages，disadvantages and developing trends of electroplated alloy coatings and thermal spray coatings on the surface of mould copper plate were summarized，as well as the main failure forms and formation mechanisms at different locations of mould surface after service under actual working conditions，providing the basis for optimizing the design of coating compositions and corresponding performance in different areas. Moreover，the service results and application advantages of the thermal spraying/vacuum diffusion composite technology developed by the project team in major domestic steel plants were introduced in detail. Finally，it was pointed out that thermal spraying technology will gradually replace electroplating technology and become the core technology of mold surface protection，and high entropy and medium entropy alloy coating has great application potential.

HfO₂ coatings with a thickness of approximately 8 μm were prepared on the refractory metals Mo surface by using chemical vapor deposition(CVD), and the reaction process of CVD HfO₂ was thermodynamically analyzed by HSC Chemistry.The microscopic morphology, self-oriented growth and nanomechanical properties of HfO₂ coatings were analyzed, and the bonding force of the coatings with the substrate and thermal shock resistance were tested. The results show that the HfO₂ coating is well bonded to the substrate, and no macroscopic flaking occurs on the surface of the coating after 100 cycles of thermal shock from 25 ℃ to 2000 ℃; the adhesion of the coating is about 23 N as determined by the scratch test; the average emissivity of the surface of the coating is 0.48 in the band of 2.5-5 μm, which improves the average emissivity of Mo in the band by nearly 5 times.

In order to enhance the physical barrier performance of polyaniline(PANI)/polyurethane(PU) coating against corrosive medium, the introduction of two-dimensional material in the coating is one of the effective methods. PU coating matrix was synthesized from 2, 4-diisocyanate (TDI) and 3, 3′-dichloro-4, 4′-diamino diphenylmethane(MOCA), and MXene@PANI was synthesized by intercalation reaction of PANI with Ti₃C₂T_x.Then protective coating of MXene@PANI/PU was obtained by adding MXene@PANI into PU. The results show that when the mass ratio of MXene/PANI is 1∶1, no obvious corrosion occurs on the surface of the MXene@PANI/PU coating after 60 days of salt spraying. The corrosion current is 3.709×10^-9 A·cm^-2, and the impedance modulus is 1.93×10⁸ Ω·cm². The reason is that MXene improves the electrochemical activity of PANI and thus enhances the electrochemical anticorrosion performance of PANI. On the other hand, MXene nanoplates as a two-dimensional barrier can prevent the corrosive medium from entering into the coating, which improves the long-term protective performance of the coating.

In order to solve the protection problem of metal parts surface, the mixed metal coating was prepared on 45^# steel by cold spraying, and then synthesized into FeCrAlCu, FeCrAlCuNi, FeCrAlCuCo, FeCrAlCuNiCo HEA coating by induction remelting technology.The effect of the addition of Ni and Co on the phase composition, microstructure, hardness and wear resistance of the FeCrAlCu series HEA coating were investigated by XRD, SEM, EDS, TEM, microhardness tester and abrasive wear tester, etc. The results show that the coating of FeCrAlCu series HEA is composed of FCC+BCC phase, and the addition of Ni element can promote the formation of FCC phase, and the addition of Co element can promote the formation of B2 phase(AlCo).The microstructure of FeCrAlCu HEA coating is dendrite. With the addition of Ni and Co, the dendrite number in the coating increases and coarsenes obviously. When Ni and Co are added at the same time, the friction property of FeCrAlCuNiCo HEA coating is the best. The hardness of the coating is 565.5HV, the friction coefficient is 0.349, and the wear rate is 3.97×10^-5 mm³·N^-1·m^-1.

Currently， the surface working temperature of second-generation or more advanced single crystal superalloy blade is above 1050 ℃， resulting in serious interdiffusion between coating and substrate. The interdiffusion not only consumes the beneficial elements of the coating and then reduces its service life， but also leads to the formation of secondary reaction zone in the substrate， which will seriously damage the high-temperature mechanical performance of the single crystal superalloy. Preparing diffusion barriers and designing the low inter-diffusivity coatings are effective ways to control the interdiffusion between thermal barrier coatings and single crystal superalloy substrates. Firstly，based on the latest international and domestic research progresses， the design principles， characteristics and classification of diffusion barriers were introduced briefly， and then the main problems and related research studies of metal diffusion barriers， ceramic diffusion barriers and active diffusion barriers were analyzed. Secondly， the application and latest progress of low inter-diffusivity coatings were reviewed， and the high-temperature protection properties and anti-diffusion mechanisms of nanocrystalline coatings， equilibrium coatings and γ′-based coatings were discussed in detail. Finally， the future development directions of different diffusion barriers and low inter-diffusivity coatings were pointed out.

In order to obtain high quality aluminium oxide tritium barrier coatings， micro-arc oxidation （MAO）technology was used to prepare micro-arc oxidation coatings on the surface of 1060 pure aluminium by doping Cr₂O₃ and graphene as additives in the electrolyte， using phosphate as the main electrolyte component. The surface morphology， elemental distribution， physical phase composition， thickness，hardness， abrasion and corrosion resistance of the micro-arc oxidation coatings were characterized by scanning electron microscope，X-ray diffractometer，eddy current thickness gauge，Vickers hardness tester， friction and wear tester， and electrochemical workstation. The results show that the surface morphology of the micro-arc oxidation coatings prepared by adding 3 g/L Cr₂O₃ and 1 g/L graphene into the electrolyte is more dense， and the proportion of α-Al₂O₃ and γ-Al₂O₃ in the coatings increases， with the thickness reaching 25.3 μm，the hardness reaching 763.01HV， and the average friction coefficient of 0.4781.At the same time，the self-corrosion potential is -0.185 V， and the self-corrosion current density is 1.095×10^-9 A·cm^-2.

To improve the surface hardness and wear resistance of Al-Pb alloys, pure aluminum (Al) surfaces coated with lead (Pb) layers were irradiated by using high current pulsed electron beam (HCPEB) to prepare Al-Pb alloyed layers with excellent properties. The surface roughness of the alloying layer was observed by 3D laser scanning microscope (LSM). Meanwhile, the micro morphology, structure and element distribution of Al-Pb coating before and after irradiation alloying were analyzed by field emission scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS). In addition, the phase composition of the alloy layer was observed by X-ray diffraction (XRD). Moreover, the surface microstructure after alloying was characterized by transmission electron microscopy (TEM). Finally, the microhardness, average friction coefficient and wear rate of the sample surface before and after irradiation were tested, and the hardness and wear enhancement mechanism were analyzed. The strengthening mechanism of the surface performance was also summarized. The internal relationship between surface microstructure and surface properties of irradiated coatings was established. The results show that after HCPEB irradiation treatment, the Al substrate and Pb coating show good metallurgical bonding, and after 30 times of irradiation, the Pb-Al alloying layer with a thickness of about 10.2 μm is prepared. Compared with pure aluminum and the original coating, the diffraction peak of (111)_Al crystal plane is widened after 30 times of irradiation, and the position of the diffraction peak is also slightly shifted to the low angle direction, which means that the Al grains on the surface of the matrix are significantly refined after the surface alloying treatment of HCPEB, and the crystal cells expand, and the lattice constant increases. HCPEB induces the formation of sub crystals, dislocations, dislocation cells, a small amount of Al(Pb) solid solution and a large number of nanoscale Pb rich particles on the sample surface. The test results show that the hardness and wear resistance of Al-Pb coating surface are significantly improved after electron beam irradiation.

In order to explore the adaptability and failure mechanism of landing gear materials for amphibious aircraft in the marine environment. By preparing a high-speed flame sprayed WC coating on the surface of hot-rolled 300M high-strength steel, the corrosion behavior of the coating in an artificial seawater environment was studied using electrochemical testing, salt spray testing, tensile testing, fatigue testing, and characterization by SEM, EDS, XRD, and CLSM. The research results indicate that the WC coating undergoes significant passivation and exhibits good corrosion resistance in an artificial seawater environment with pH value 8.2, which is related to the passivation of Co in the coating under alkaline conditions. The long-term electrochemical impedance results indicate that the corrosion resistance of the coating increases after soaking for 28 days, which is related to the oxide formed by the surface binder. Compared with the 300 M substrate, the tensile strength of the sprayed material slightly increases, which is related to the residual stress releasing inside the coating. Its cracking in artificial seawater is mainly controlled by the anodic dissolution process. As the pre corrosion time increases, the fatigue life of the material significantly decreases. The corrosive medium from the environment enters the interior of the coating during the pre corrosion process, which increases the number of defects, causes premature failure of the coating, and leads to an increase in material fracture sensitivity. WC coatings have good corrosion resistance, and the release of residual stress during the tensile process slightly increases the tensile strength of the material. The coating fails prematurely after pre corrosion, which results in a reduced fatigue life of the material.

Plasma spray-physical vapor deposition(PS-PVD) technology which has many characteristics of the multi-structure regulation, provides the possibility for the preparation of thermal barrier coatings with high thermal insulation and long life. It is one of the key technology to realize the development of high performance aero-engine. The unique microstructure of PS-PVD columnar structure coatings has dual advantages of high thermal insulation and long thermal cycle life, and has broad application prospects in the field of thermal barrier coatings for aircraft engines. However, the process control of PS-PVD columnar structure coating is achieved on the basis of a large number of experiments, and there is a lack of relevant theoretical research. Moreover, the CaO-MgO-Al₂O₃-SiO₂(CMAS) corrosion failure problem faced by the columnar structure coating with high porosity restricts the use of the coating. The influence of deposition unit phase states on the coating structure was described from the structural characteristics of the coating, and the vapor deposition mechanism of columnar coating was revealed. Based on the phase transition of coating material in the jet, the essence of process parameters regulation was clarified. In addition, the corrosion mechanism of CMAS and the corrosion resistance mechanism of Al-modified coating were investigated. Finally, the structure control and performance improvement of PS-PVD coating and the application of PS-PVD technology in environmental barrier coatings and functional films were prospected.

Thermal barrier coatings， consisting of a metal bonding layer， ceramic surface layer， and thermal growth oxide， are widely utilized in turbine blades for aero engines as protective coatings. The LaZrCeO/YSZ double ceramic thermal barrier coating was prepared on a Ni-based superalloy matrix using EB-PVD technology. The composition， phase structure， and thermal cycle life of the thermal barrier coating were investigated by adjusting the deposition energy of the ingot. Furthermore， the failure mechanism of the thermal barrier coating under 1100 ℃ thermal cycle was analyzed. The results indicate that the Zr content in the LaZrCeO coating increases proportionally with the rise in ingot deposition energy， while maintaining a consistent La/Ce ratio. Additionally， the increase in evaporation electron beam leads to changes in coating phase structure from single fluorite phase to compound pyrochlore and fluorite phase structure， and finally to single pyrochlore structure. Thermal cycling tests at 1100 ℃ demonstrate that the average thermal cycle life of LaZrCeO/YSZ ceramic thermal barrier coating with composite pyrochlore and fluorite phase structure reaches 1518 cycles， indicating excellent thermal physical properties. As the thermal cycle progresses， the Al element in the bond coat diffuses outward to form a thermally grown oxide （TGO） layer， while the Cr element reacts with LaZrCeO and oxygen to generate LaCrO₃ and ZrO₂. At elevated temperatures， Ni and Co elements diffuse and react with oxygen to produce （Ni，Co）（Cl，Al）₂）O₄ compounds. The chemical reactions induce cracks in either the TGO layer or the interface layer， reducing the toughness between the metal bond layer and ceramic layer， and leading to thermal barrier coating failure.

Partially stabilized zirconia （7YSZ） with a mass fraction of 7±1% yttrium oxide is a widely used ceramic material for thermal barrier coatings. However， its phase stability， sintering resistance， and mechanical properties decreased during the long-time operation above 1200 ℃. A new type of Sc₂O₃-Y₂O₃ co-doped ZrO₂ thermal barrier coating ceramic material was proposed， and a molar fraction of 7.5%Sc₂O₃-x%Y₂O₃-（92.5-x）%ZrO₂（x=0，0.1，0.2，0.3） ceramics were prepared by solid-state reaction method. The effects of Y₂O₃ doping on the microstructural， phase evolution， and mechanical properties（including Vickers hardness， fracture toughness， elastic modulus and three-point bending strength）were explored by XRD， SEM， and other testing methods. The results show that the relative density of Sc₂O₃-Y₂O₃ doped ZrO₂ ceramics sintered at 1450 °C for 3.5 h is more than 97%， and the phase structure is composed of tetragonal phase. Compared with 6-8YSZ ceramics， Sc₂O₃-Y₂O₃ doped ZrO₂ ceramics exhibit similar Vickers hardness （13-14 GPa）， fracture toughness （6.5-7.0 MPa·m^1/2）， elastic modulus （211-214 GPa）and three-point bending strength（520-850 MPa）. Fracture mechanism shows a mixture of transgranular and intergranular fracture modes， in which transgranular fracture is dominant.This ceramic can be explored as a potential thermal barrier coating material for high-temperature applications.

NiCoCrAlYHf coating （HY5 coating） was prepared on DD6 alloy by vacuum arc ion plating method. After different diffusion temperature treatments， the ceramic coating was deposited by electron beam-physical vapor deposition（EB-PVD） method. The cyclic oxidation properties of thermal barrier coatings at different diffusion temperatures were investigated by analysing the phase composition and microscopic morphology of bond coating（BC） at different diffusion temperatures. The results show that the bond coating samples after diffusion treatment in a vacuum change from the single-phase structure of the deposited to the double-phase structure of the diffusively treated. The content of β-NiAl phase in the bond coating increases with the increase of diffusion temperature. After diffusion treatment， the coating surface is uniform and dense， gray-white and black phases are observed in the coating， the black phase is β-NiAl， and the gray-white phase is γ-Ni and γ'-Ni₃Al phases， which demonstrates that diffusion treatment can change the phase structure of the bond coating. The coating with 900 ℃ diffusion treated has the longest cyclic oxidation life， exceeding 400 h； the cyclic oxidation life of 1100 ℃ diffusion treated coating is less than 300 h. When the diffusion temperature is 900 ℃， the oxidation rate of the bond coating and the thermally grown oxide thickening rate are the lowest. It is not that the more β-NiAl phase content the better， but there is a threshold in the phase composition， increasing the β-NiAl phase content within the threshold can obtain better service performance.