This study investigates the thermal cycling behavior of HVOF-MCrAlY combined with APS-nanostructured YSZ（nYSZ） thermal barrier coatings（TBCs） produced using three commercial MCrAlY powders commonly utilized by gas turbine original equipment manufacturers（OEMs） and maintenance, repair, and overhaul（MRO） companies, within a temperature range from ambient to 1150 ℃. Among the coatings, HVOF-A386-2.5+APS-nYSZ exhibits the longest furnace cycle testing（FCT） life, while HVOF-A9624+APS-nYSZ has the shortest. However, the differences in FCT life among the three TBCs are insignificant. All three coatings fails in a manner similar to conventional HVOF-MCrAlY+APS-YSZ（mYSZ） coatings, primarily due to crack propagation and coalescence in the APS-YSZ layer near the YSZ/MCrAlY interface, resulting from interface separation at mYSZ/nYSZ and mYSZ/mYSZ interfaces. The thermally grown oxide（TGO） layer grows fastest on the HVOF-A9624 surface, whereas the growth rate is slowest on the HVOF-A386-2.5 surface. However, the variations in TGO growth rates among the three coatings are relatively small. It is anticipated that increasing the surface roughness of the HVOF-MCrAlY may strengthen the YSZ/MCrAlY interface, thus mitigating crack propagation and coalescence in the TBC. Additionally, reinforcing the YSZ/YSZ interface can enhance resistance to interface separation and surface cracking. Furthermore, controlling the aluminum（Al） content in the MCrAlY and/or doping alloy elements into the MCrAlY may slow down diffusion, reducing the TGO growth rate and preventing excessive formation of mixed oxides. These strategies may collectively contribute to improving the durability of HVOF-MCrAlY+APS-YSZ TBCs under thermal cycling conditions.

The objective of this work is to investigate the effects of pre-exposure on the CMAS corrosion behavior of doped and modified Gd₂O₃-Yb₂O₃-Y₂O₃（GYb-YSZ） thermal barrier coatings. Three types of test, such as high-temperature pre-exposure test, CMAS corrosion test, and CMAS corrosion test after high-temperature pre-exposure, are conducted by preparing standard specimens. The changes in microstructure and basic mechanical properties of the coatings after these types of test are comparatively studied using scanning electron microscopy（SEM） and nano indentation, thereby discussing the impact of pre-exposure on CMAS corrosion. The results show that short-term pre-exposure treatment leads to multi-channel penetration, while long-term pre-exposure treatment results in the occurrence of longitudinal through-cracks. Pre-exposure to 980 ℃ or 1050 ℃ for 125 h reduces the penetration effect of CMAS. When the temperature reaches 1150 ℃, CMAS penetrates the top coat in the molten state. In the process of cooling, CMAS re-solidification causes to form vertical cracks resulting from the expansion of columnar grain boundaries, extending through the top coat, and accelerating the spallation of the coating. Meanwhile, after CMAS corrosion, the coating shows a significant increase in Young’s modulus of 48% and hardness of 50% compared to the original sample. Thus, the specimens exhibit significant resistance to CMAS corrosion under pre-exposure treatment at 980 ℃ or 1050 ℃ for 125 h.

The three-layer structure molybdenum-silicon high-temperature oxidation-resistant coating was prepared on selective laser melting Ta10W alloy by slurry sintering process. The microstructure and element distribution of the Ta10W alloy and coating were characterized by SEM and EDS. The tensile properties, microhardness of the Ta10W alloy and coating, and the coating bonding strength were tested. The results show that the coating of selective laser melting Ta10W alloy is divided into three layers: outer, sub-outer and inner layers. The outer layer is TaSi₂ and MoSi₂ phases, the sub-outer layer is TaSi₂ phase and dispersed Ta₅Si₃ phase, and the inner layer is Ta₅Si₃ phase. The yield strength, tensile strength and uniform elongation of the coating and remove coating specimens are 639, 647 MPa, 13.6%, and 602 MPa, 675 MPa, 22.7%, respectively. Compared to the Ta10W alloy specimen, the uniform strain of the remove coating specimen is increased by 5.5%. The reason for this is that the thermal effect in the coating preparation process eliminates the residual stress of the Ta10W alloy formed by selective laser melting. The yield strength of the coated specimen is increased by 37 MPa due to the application of the coating. The microhardness of the outer layer, sub-outer layer, inner layer and Ta10W alloy were 550HV_0.2, 1120HV_0.2 , 534HV_0.01 and 307HV_0.2, respectively. The average coating bonding strength is 63 MPa, which is higher than that of the ceramic and high entropy alloy coatings. This is due to the fact that the three-layer coating has a good metallurgical bond to the Ta10W alloy.

Corrosion problem resulting from alternating ambient salt spray and high temperature oxidation poses a great threat to the safe service of aircraft engine during frequent start-stop in marine environment. In the present study, Ni25Cr5AlY coating is prepared on top of GH4169 superalloy substrate by direct-current（DC） magnetron sputtering. Corrosion behavior of the Ni25Cr5AlY coating is systematically studied by designing three different test conditions: high temperature oxidation at 1000 ℃, ambient salt spray, and alternating ambient salt spray and high temperature oxidation. The phase constitution and morphology of the corrosion products are analyzed by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The results indicate that after 168 h oxidation at 1000 ℃, the coating forms a dense and continuous Al₂O₃ scale which resists well against the oxidizing environment, while the coating suffers from pitting locally after 168 h salt spray test. After 168 h exposure to alternating ambient salt spray and high temperature oxidation test, the Al₂O₃ scale formed on the coating is damaged owing to the chlorine induced active oxidation mechanism, eventually resulting in Cr₂O₃ scale formation. In addition, the Cr₂O₃ scale is porous and cracks locally, which causes accelerated corrosion of the coating and internal oxidation of the coating and substrate. The corrosion degradation of the coating is accelerated under the synergistic effect of salt spray and high temperature oxidation. The GH4169 superalloy without the coating experiences severe scale spallation after 168 h exposure to the alternating test, featured by forming a poorly protective NiO scale with prevalent internal oxidation.

The aircraft engine is considered the “heart” of the aircraft. The development of advanced aircraft engines focuses on achieving a high thrust-to-weight ratio, high efficiency, low fuel consumption, and extended operational life. High-temperature functional coatings, such as thermal barrier coatings（TBCs）, thermal/environmental barrier composite coatings（T/EBCs）, and high-temperature stealth coatings, are applied to critical hot-end components of aircraft engines. These coatings play a significant role in enhancing the service performance, operational life, safety and reliability of the engine. Taking TBCs, T/EBCs, and high-temperature stealth coatings as examples, this paper provides a systematic overview of recent research progress in the design of high-temperature functional coating materials, coating preparation science and technology, and coating performance evaluation and characterization, both domestically and internationally, with a specific focus on the advancements made at Beihang University. Furthermore, challenges and development trends faced by new high-temperature functional coatings of advanced aircraft engines in the future are also discussed. In the future, the research focus of advanced high-temperature functional coatings will shift toward multifunctional composite coatings, enhanced adaptability to extreme environments, and improved process compatibility.

As the turbine inlet temperatures of aero engines continue to rise, there is an urgent need to develop a new generation of single-crystal superalloys and their thermal protective coatings for turbine blades. In order to meet the stringent requirements for the comprehensive performance of high-temperature structural materials in the complex service environments of aero engines, the intelligent design research of single crystal superalloys and thermal protection coatings has been gradually carried out at home and abroad in recent years under the promotion of material integrated computational engineering and material informatics. This paper reviews the latest research progress in the design of novel single-crystal superalloys and thermal protective coatings by utilizing multi-scale computational simulations and machine learning methods. The findings confirm that multi-scale computational simulations offer robust theoretical support for understanding the strengthening and toughening mechanisms of single-crystal superalloys, as well as the oxidation resistance and diffusion protective mechanisms of thermal protective coatings. Additionally, the study highlights the reliability and significant potential of machine learning in constructing intrinsic "composition-structure-property" relationship for high-temperature structural materials. This approach paves an intelligent and efficient new pathway for the rapid development of next-generation high-temperature single-crystal superalloys and thermal protective coatings.

With the global energy transition and increasing environmental requirements, hydrogen-mixed gas turbines as a high-efficiency and low-emission energy conversion equipment has been widely concerned. This paper reviews the development status of hydrogen-mixed gas turbines domestically and internationally, analyzes the characteristics of hydrogen combustion in gas turbines, explores the impact of hydrogen combustion on complex components and the application of high-temperature materials, and analyzes the performance requirements for hot-end component materials operating under high temperature, high pressure, and corrosive conditions, as well as the main challenges and potential solutions in current material development. The effects of water vapor and hydrogen embrittlement during hydrogen combustion on gas turbine alloys and thermal barrier coatings are discussed in detail.Water vapor accelerates the oxidation and corrosion of alloys, leading to a decline in mechanical properties. Furthermore, hydrogen embrittlement significantly affects the toughness and durability of alloys, increasing the risk of crack propagation and fracture. In terms of the problems, future research should focus on multi-field coupling simulations and accelerated corrosion tests, considering the factors such as temperature, pressure, and different atmospheres to establish realistic environment simulators to evaluate alloy and coating performances. Additionally, the combined effects of hydrogen and water vapor on high-temperature alloys and thermal barrier coatings should be emphasized. This includes investigating the diffusion mechanisms of hydrogen in alloys, interactions with lattice defects, and the microscopic processes leading to hydrogen embrittlement. Building oxidation models in high-temperature water vapor environments, clarifying the dissociation and adsorption mechanisms of water vapor at high temperatures, the hydroxylation of protective oxide films Al₂O₃ and Cr₂O₃, and the growth behavior of non-protective oxides（e.g., spinel） are also essential.

The types, preparation methods, thermal and mechanical properties of rare earth hafnate materials and their corrosion behaviors exposed to low melting point silicate（CMAS） and high temperature water vapor are summarized. The previous investigations indicate that the rare earth hafnates have the characteristics of low thermal conductivity, excellent high-temperature phase stability and good resistance to CMAS corrosion, which shows a favorable application prospect in the field of thermal/environmental barrier coatings（T/EBCs）. However, in order to overcome the limitations of a single-phase rare earth hafnate exposed to water vapor corrosion and CMAS, it is still necessary to carry out systematic studies on multi-rare earth components/high-entropy rare earth hafnate in the future, and further clarify the mechanism of influence of lattice distortion caused by components on physical and chemical properties of materials. Moreover, the coupled control method of thermal, mechanical and chemical properties of hafnate with integrated functions such as thermal protection, water vapor corrosion resistance and CMAS resistance and their corresponding material preparation processes should be explored.

The Si/Mullite+BSAS/Yb₂Si₂O₇ tri-layer environmental barrier coating was prepared on the surface of the SiC substrate by atmospheric plasma spraying using solid-state sintering Yb₂Si₂O₇ feedstock. Scanning electron microscope （SEM）, energy dispersive spectrometer （EDS）, X-ray diffraction analyzer （XRD） and nanoindentation testing machine etc were employed to study the microstructure, phase composition, and mechanical properties of the coating. The results indicate that the powder is composed of 83% Yb₂Si₂O₇ phase and 17% Yb₂Si₂O₇ phase, the porosity of the Yb₂Si₂O₇ layer obtained by plasma spraying is （6.61±0.65）%, the bonding strength of the coating is （22.82±3.55）MPa and the fracture toughness of the coating is （1.98±0.12）MPa·m^1/2. Furthermore, the water-oxygen corrosion test results of the coating at 1350 ℃ show that the monoclinic phase contents of the Yb₂Si₂O₇ phase decrease first and then increase. The thermally grown oxide SiO₂ formed by high-temperature oxidation of the silicon bonding layer is compatible with Mullite+BSAS, and interdiffusion between Mullite+BSAS and Yb₂Si₂O₇ layers isn’t detected. Deterioration of the silicon layer is a major limiting factor in the lifetime of the coating.

Silicon carbide fiber-reinforced silicon carbide ceramic matrix composites（SiC_f/SiC） used in aero-engines are damaged or even failed due to the oxidation and corrosion by high-temperature and high-speed combustion gases. In this work, the gas generation device was used to simulate the complex gas environment in the aircraft engine, and the aviation kerosene mixed with liquid oxygen fuel in a certain proportion was ignited to form a high-temperature and high-speed combustion gas to assess the material. The oxidation test for 10 h and thermal shock test for 1000 cycles in combustion gas environment at 1200 ℃ were conducted on SiC_f/SiC composites respectively. And the protective effect of environmental barrier coating（EBC）on SiC_f/SiC composites was investigated. Uniaxial tensile tests were conducted on SiC_f/SiC composites and SiC_f/SiC-EBC composites after combustion gas environment assessment, and their fracture and cross-section micro-morphologies were observed by scanning electron microscopy. The results show that no significant oxidation of fibers and interphases is found in SiC_f/SiC composites and SiC_f/SiC-EBC composites after oxidation for 10 h in combustion gas environment, and their uniaxial tensile strength decreases by less than 2%. After 1000 thermal shock cycles in combustion gas environment, multiple micro-cracks are formed and oxidative corrosion of the interfacial layer occurs inside the SiC_f/SiC composites, and the uniaxial tensile strength decreases by 41.3%. The EBC coating can effectively protect the SiC_f/SiC composites from oxidation and corrosion of high-temperature gas, and the uniaxial tensile strength of SiC_f/SiC-EBC composites decreases by 16.6% after 1000 thermal shock cycles.

Since the application of electromagnetic technology, the investigation of microwave absorbing materials has been widespread concerned in the world. With the development of technology, the effect of microwave absorption technology is constantly increasing in the world. Up to now, the structural design and electrical performance simulation calculation of microwave absorption coatings play an increasingly important role in the preparation of microwave absorption coatings. The design and optimization of coating structure can directly improve the absorption performance. Nowadays, microwave absorbing materials usually have multi-layer structures such as impedance matching layer, absorption layer and bonding layer. Their reflection coefficients are determined by the thickness, magnetic permeability, and dielectric constant. Only relying on the experiments to study the influence of reflection coefficient must be inevitably resulted in a relatively broad and blind workload. Based on this, three kinds of microwave absorption coating absorbers were selected to carry out electromagnetic parameter testing and analysis. The electromagnetic properties of single layer, single layer and double layer structure combined with two kinds of absorbers were simulated and calculated under the 1.2 mm thickness of the coating. Four optimal coating design schemes were obtained through the simulation calculation, and the electrical performance experiment were further completed for comparison. The results show that the electrical performance verified by experiment is in good agreement with the trend of simulation calculation results. Finally, the optimal coating is the single-layer coating with the Absorbent A∶ Absorbent C=2∶1. At this time, the simulation calculation and experimental results of the microwave absorption coating both show relatively high absorption performance.

With the application of shrouds made of silicon carbide ceramic matrix composite（SiC-CMCs）, the abradable coating technology suitable for SiC-CMCs is urgently needed. The four-layer structure of BSAS（Ba_0.75Sr_0.25Al₂Si₂O₈）-polyester-based abradable environmental barrier coating （A/EBCs） was prepared by atmospheric plasma spraying. The influence of process parameters on the porosity and the structural evolution of the layer at 1300 ℃ were investigated. The phase structure, microstructure and coating composition were characterized by XRD, SEM, EDS and TEM respectively. The results show that the porosity of BSAS-polyester abradable top layer is 26.4%-36.8%. And the temperature-sensitive parameters of BSAS-polyester particles are primary gas （argon） flow, second gas （hydrogen） flow and spraying distance. In contrast, the speed-sensitive parameters are primary gas （argon） flow. The primary gas （argon） flow has the opposite effect on the particle temperature and velocity of the BSAS-polyester. The abradable surface layer is oxidized at 1300 ℃ for 300 h and maintains monoclinic phase structure, stable stucture and composition, and locally precipitates spherical amorphous silicon oxide particles. Furthermore, the coating abradability was evaluated by high-temperature and high-speed scraping test. Nano-scale Ni-based superalloy particles adhesion on the surface of the coating are found, and the blade incursion depth ratio （IDR） is 20%, which meets the requirements of the abradable sealing coating.

To investigate the corrosion behavior of NiCrAl-NiC sealing coating in high-temperature molten salt environments, NiCrAl-NiC sealing coating was prepared using atmospheric plasma spraying technology. By measuring the weight loss of NiCrAl-NiC sealing coating, the dynamic changes of the coating were studied. The thermal corrosion behavior of NiCrAl-NiC sealing coating in a mixture of thiochlorate（75% Na₂SO₄ + 25% NaCl）at 650 ℃ was discussed using scanning electron microscopy（SEM）, X-ray diffraction（XRD）, laser confocal microscopy, and other methods. The results show that after 10 h of hot corrosion experiments, the NiCrAl-NiC sealing coating exhibites a rapid weight gain state, with a weight gain rate of 32.041 mg²·cm^–4·h^–1. After conducting a 20 h hot corrosion experiment, the coating experienced weight loss due to the detachment of the surface oxide film. After 30 h of hot corrosion, the growth of the facial mask on the coating surface covers the entire coating. The surface morphology of the coating is uniform, and the surface pores are reduced, which can play a good role in protecting the substrate. Under the protection of a complete oxide film, the mass change rate of the NiCrAl-NiC sealing coating after a 40 h hot corrosion experiment is 0.064 mg²·cm^–4·h^–1. Through XRD testing, it is found that the composition of the oxide film on the surface of the coating after hot corrosion is mainly NiO and NiCr₂O₄. During the hot corrosion process, the spinel structure of NiCr₂O₄ hinders the hot corrosion of the coating, which is the main reason for the slow corrosion process of the coating.

In this paper, TWL12 + TWL20 inorganic salt aluminum coating was sprayed on the surface of Ni-based P/M superalloy. The microstructure changes of inorganic salt aluminum coating and P/M superalloy after high temperature oxidation at 700, 750 ℃ and 800 ℃ were studied by XRD, SEM, EPMA and TEM. The results show that after high temperature oxidation, the surface structure of the coating peels off, and the aluminum in the coating diffuses with the substrate to form a transition layer composed of oxidation zone, diffusion layer and interdiffusion zone. The oxidation zone is the outermost layer, where is mainly enriched with O and Al elements to form Al₂O₃ layer. The diffusion layer mainly contains Ni and Al elements, forming NiAl phase and α-Cr phase dispersed in it. Finally, the interdiffusion zone rich in Ti, Cr, Co, Ta and other elements exists between the diffusion zone and the matrix, which is mainly composed of Ni₂AlTi phase matrix and σ phase dispersed in it. The analysis shows that the thickness of transition layer changes with the increase of oxidation temperature, it is mainly manifested by the increase of the width of the interdiffusion zone, the increase of the size of α-Cr phase in the diffusion layer and σ phase in the interdiffusion zone, and the growth trend of σ phase along the vertical transition zone is intensified. The oxidation weight gain curve shows that the transition layer exhibits good oxidation resistance during high temperature oxidation at 750 ℃ and 800 ℃ after the surface structure of the coating falls off, it indicates that the TWL12 + TWL20 inorganic salt aluminum coating has the potential to provide high temperature oxidation coating protection for advanced P/M superalloy used in aeroengines.

The（Ni, Pt）Al bond coats were prepared on the surface of nickel base single crystal superalloy by chemical vapor deposition（CVD）, and then YSZ ceramic coats were directly deposited on the surface of bond coats by electron beam physical vapor deposition（EB-PVD）.The influence of phase constituent of bond coat on the cyclic oxidation behavior of （Ni, Pt）Al/YSZ thermal barrier coatings was investigated in detail. The phase structure, morphology and chemical composition of the coatings were analyzed. The experimental results show that the bond coat is mainly composed of β-（Ni,Pt）Al and PtAl₂ phases and the contents of the as-deposited bond coat are primarily including Ni, Al, Pt, Co and Cr elements. The spallation location of the TBCs probably occurs at the interface of TGO layer and bond coat, inside of TGO layer and within the bond coat. After thermal cycling test, it is found that the spallation may occur in the interior and interface of TGO and adhesive layer. With the extension of thermal exposure time, the residual stress located at the TGO layer decreases gradually in total. Therefore, controlling the precursor activity, Pt/Al element content, inhibiting the formation of brittle PtAl₂ phase, improving the interfacial toughness of TGO layer/bonding layer, and reducing the stress-strain level of TGO layer are important ways to extend the thermal cycling life of（Ni, Pt）Al/YSZ thermal barrier coatings.

Continuous SiC fiber reinforced titanium matrix composite（SiC_f/Ti composite）has good specific strength and comprehensive mechanical properties, it is a lightweight high temperature structural material that attracts much attention in the new generation of equipment development. SiC_f/Ti composites can be prepared by the methods of foil fiber foil（FFF）and matrix coating fiber（MCF）. In order to compare the effects of the two methods on the growth of interfacial reaction, SiC_f/TC17 composites were prepared by FFF and MCF respectively. By study the interfacial reaction layer thickness of composites prepared by the two processes after thermal exposure at the temperature from 800℃ to 900 ℃, the microstructure and the thickness of interfacial layer were analyzed by scanning electron microscope, further the interfacial reaction rate at high temperature was obtained, and the interfacial reaction kinetic parameters of different materials were attained. The results showed that the interfacial reaction rate of SiC_f/TC17 composite prepared by MCF method was higher than that of the composites prepared by FFF method at the same temperature. The interfacial reaction rate factor k₀ is 4.942×10⁻³ m/s^1/2 and 8.149×10⁻³ m/s^1/2 for the composites prepared by MCF and FFF method, respectively. Additionally, the reaction activation energy Q is 276.3 kJ/mol and 291.7 kJ/mol for those, respectively. This is because the titanium alloy matrix prepared by MCF method has smaller phase structure and higher element diffusion rate at high temperature. Therefore, the composite prepared by MCF has lower reaction activation energy at high temperature.

Thermal barrier coatings, which are widely used in aero-engines and gas turbines, can reduce the surface temperature and improve the effective service time of superalloy due to low thermal conductivity and good temperature resistance. The performance and lifetime of the thermal barrier coating are directly affected by the material and structure of the ceramic top coating. The method of adjusting the microstructure of ceramic coating with controlled raw material powder can reduce the strain-stress mismatch in the coating, and has the advantages of flexible operation, remarkable effect and wide control range. In order to solve problems of low strain tolerance and insufficient thermal shock resistance in traditional coatings, our team successfully has prepared ceramic microspheres with hierarchy pore structure by using electrostatic spraying combined with phase inversion theory（ESP）. Compared with traditional hollow microspheres, the ESP microstructure of nano-pores and finger-like pores lead to high sintering resistance, low thermal conductivity, high specific strength and >95% thermal reflectivity. With the retention of the hierarchy structure, the coating has good fracture toughness and strain tolerance, where the thermal cycle life of the coating is increased by more than ~2 times. ESP technology provides a fast feedback control method for new thermal barrier coating materials from material design to engineering application, such as rare earth zirconate, rare earth tantalate and rare earth doped YSZ high entropy system. With the in-depth study of material mechanics, optics, thermodynamics and the precise control of internal topological structure, the hierarchy pore structure will be more widely used in aerospace, military defense, fluorescence temperature measurement and other fields in the future.

The corrosion behavior and mechanism of environmental sediment（CMAS molten salt）on different YO_1.5-doped zirconia coatings（8YSZ, 38YSZ and 55YSZ）sprayed by atmospheric plasma at 1300 ℃ have been systematically studied. The results show that the 8YSZ coating has severe CMAS corrosion. At the matrix/CMAS interface, non-protective C-ZrO₂ containing Ca and low Y content is formed by dissolution-reprecipitation, accompanied by obvious grain boundary corrosion. For 38YSZ and 55YSZ coatings containing high YO_1.5 doping content, along with the reaction, in addition to spherical C-ZrO₂, protective products of apatite and garnet are also formed, which can effectively prevent further erosion of CMAS molten salt. Moreover, 55YSZ coating shows better resistance to CMAS molten salt corrosion than 38YSZ coating. From the optical basicity perspective, the higher the YO_1.5 content, the higher the reactivity between coating and CMAS molten salt, the easier it is to generate stable products in CMAS molten salt. From the reaction process analysis, high YO_1.5 content can promote Y³⁺ in CMAS molten salt saturation, and then generate more stable, continuous phase（such as apatite, garnet）, avoid matrix material and CMAS molten salt further contact and reaction, thus improving the corrosion resistance of CMAS.

In order to develop a self-lubricating coating with long life and high reliability suitable for harsh working conditions, the composite coating with NiCoCrAlYTa as matrix phase, Ag as lubricant phase and Mo as the reinforcing phase were prepared by high-velocity oxy-fuel spraying（HVOF）technology. The high-low temperature cycling tribological properties of the composite coating were investigated at 25 ℃ and 800 ℃. The morphology features, chemical composition and phase structure of the worn surface were studied to reveal the interaction between different elements in the friction process and physicochemical nature of friction interface. In addition, the multi-cycles adaptive lubrication mechanism under the alternating environment of high and low temperature was explored as well. The results show that the composite coating is dense and uniform, and has better mechanical properties. The phases of the composite coating mainly contain γ-Ni, β-NiAl, γ'-Ni₃Al, Ag and Mo. The β-Ag₂MoO₄ layer-like lubricant generated on the surface can greatly improve the friction and wear performance of the composite coating at high temperature. Under the condition of multi-cycles, the friction coefficient of subsequent cycle of the composite coating is increased compared with the first cycle, but the wear rate of the composite coating at room temperature is decreased. This is caused by the interaction between the lubricating phase of β-Ag₂MoO₄ and the hard phases of Al₂O₃ and MoO₃ with the action of frictional shear force.

Rare-earth silicate environmental barrier coatings（EBCs）are important materials for the application in hot end components of new generation high thrust-to-weight ratio aero engines. However, the rare-earth silicate top layer is prone to form longitudinal cracks, which provides a channel for corrosive media to enter the interior of the EBC system, causing oxidation and cracking of the silicon bond layer, ultimately leads to the failure of EBCs under high temperature service environment. MoSi₂ has excellent high-temperature properties and is expected to improve the high-temperature stability of rare-earth silicate EBC systems. In this work, three kinds of EBCs with Yb₂SiO₅, Yb₂SiO₅-5%MoSi₂（Volume fraction, the same below）and Yb₂SiO₅-10%MoSi₂ as the top layer, Yb₂Si₂O₇ as the intermediate layer and Si as the binder layer were prepared by vacuum plasma spraying（VPS）technique respectively. The morphological changes of the coating before and after thermal shock at 1350 ℃ were characterized by field emission scanning electron microscopy. The doping of MoSi₂ not only improves the damage tolerance of the Yb₂SiO₅ coating, but also consumes the oxidizing medium and reduces its diffusion into the interior of the coating system, which reduces the thickness of the TGO layer on the bonded layer by 83% and 88% and effectively improves the high-temperature stability of the coating system.

ZnO is currently the main coating material for piezoelectric bolt sensors, which exhibits excellent acoustic-electric signal conversion because of its unique piezoelectric effect, but its high-temperature structure and performance stability have been less studied. In this paper, ZnO piezoelectric coating that could generate ultrasonic longitudinal waves was prepared on （100）_Si and industrial titanium bolts by RF magnetron sputtering, and annealed at different temperatures and different time durations to investigate the effects of high-temperature annealing treatment on the structure and properties of the coating. The results of scanning electron microscopy show that the annealing treatment below 600 °C does not affect the microscopic morphology of the coating surface, and the cross-sectional morphology of the coating shows a columnar crystal structure, and the columnar crystals tend to merge with the temperature increased. The results of atomic force microscopy show that the surface roughness of the coating varies by ±4 nm, and the X-ray diffraction results show that different annealing temperatures do not affect the crystal structure of the coating significantly. The acoustic signals of the bolt samples after annealing treatment at different temperatures and durations are examined, and the results show that the coating surface is intact after annealing treatment at 500 °C and below, and the bolt coating is completely peeled off after annealing treatment at 600 °C. The ultrasonic signals characterize that the structure of coating is stable after annealing at 500 °C or below; at 300 °C, after a long annealing treatment, none of the excitable ultrasonic properties of the bolt samples are destroyed, indicating that the ZnO coating can serve in the temperature range of 300 ℃ for a long time.

The two-dimensional finite element microscopic model of NiCoCrAlY/YSZ gradient thermal barrier coating was established by using the representative volume element method to calculate the thermophysical properties of the gradient layer under different composition ratios. The parameter results were extended to the three-dimensional multi-layer solid model to study the thermodynamic properties of the double-layer coating and gradient structured coating under thermal cycling condition. The results show that the elastic modulus, Poisson's ratio, coefficient of thermal expansion and thermal conductivity of the gradient layer are approximately linear with the component proportion of each phase, and the thermal conductivity is also affected by the distribution pattern of each phase. The thermal conductivity is low and the highest value is 2.91 W·m⁻¹·K⁻¹ when the proportion of NiCoCrAlY phase in the gradient layer is below 0.7 at room temperature. Compared with the double-layer coating, the proportion of YSZ in gradient coatings is reduced by 20%, the insulation temperature is reduced by 14%, the radial tensile stress, axial tensile stress, and shear stress of the ceramic surface layer at high temperature are reduced respectively by 47%, 32% and 37%, and the residual stress after cooling is reduced by 50%. The results are attributed that the gradient of the coating structure can effectively reduce the thermal mismatch stress caused by the difference in the thermal expansion coefficient between coating and substrate. According to the results of coating stress distribution, the coating is inclined to form vertical cracks in the centre region and horizontal cracks near the outer edge of the TC/BC interface.

The process of charge accumulation and dissipation on the surface of rGO / CNTs / EP composite coating was analyzed theoretically, and the fitting analysis was carried out according to the experimental data. The rationality of the theoretical model and the factors affecting the charge dissipation were discussed. On this basis, three kinds of charge dynamic change models were adopted to fit the measured data analysis, revealed the fitting curve and charge accumulation and dissipation process parameters such as time constant, fitting coefficient, and compared with the theoretical change curve, verified the charge and time constant, the relationship between the changes of the rationality of the evaluation model with a coating of charge dissipation effect. The results show that: compared with the accumulation model, the complex model better reflects the change process of charge accumulation process. With the increase of rGO / CNTs content in the coating, the ratio of accumulation time constant to dissipation time constant increases, the peak value of accumulated charge decreases and the dissipation effect increases. The dissipation model is basically consistent with the actual trend of charge dissipation process. With the increase of rGO / CNTs content, the dissipation time constant decreases and the dissipation effect increases.

7% yttria stabilized zirconia (7YSZ) thermal barrier coatings (TBCs) prepared by air plasma spray were laser-remelted, and subsequently pre-heated and Al₂O₃ sol-gel repaired for restraining the crack growth in the remelted coatings. The as-prepared coatings were exposed to high temperature molten CaO-MgO-Al₂O₃-SiO₂ (CMAS) to explore their corrosion resistance. The results show that both the laser remelted and the pre-heated, the laser-remelted coatings are densified by CMAS attack. In addition, the thickness of the densified layers is on the same order of that of the non-remelted coatings. Despite of this, the densified layer in the laser remelted coating repaired by Al₂O₃ sol-gel is much thinner than the other coatings. This indicates that Al₂O₃ sol-gel repairing coupling with laser-remelted method can effectively improve the CMAS resistance of 7YSZ TBCs due to the refractory anorthite generated during corrosion process. This refractory compound produced between CMAS and Al₂O₃ sol-gel is capable to decrease the mobility and corrosivity of the CMAS.

The MCrAlY bond coats used for thermally-sprayed thermal barrier coatings applied to aeroengines and industrial gas turbines are reached their temperature limits. The further development is aiming to extend service life, low production cost and compatibility with new fuels. The new MCrAlYs have to be oxidation resistant and spallation resistant, and able to prevent SRZ formation caused by the diffusion with superalloy substrate, and to avoid the damage of thermo-mechanical properties. This paper reviewed recent developments in this area, and proposed a composite structured low-β / near-γ′ type MCrAlY with a very low ϕ value and CTE closed to Al₂O₃ to achieve the target. This approach may be cost effective, and more attractive to aeroengine and industrial gas turbine manufacturers, as well as coating developers and research institutions. Meanwhile, big data analysis will help to design new coating composition, speed up the development process and reduce R&D cost, lead to the findings of more durable thermal barrier coatings for aeroengine and industrial gas turbine applications.

CeO₂-8YSZ (CYSZ) composite agglomerated powder was synthesized by spray drying of 20% micron-scale CeO₂ powder doped with nano-ZrO₂-8 mol% Y₂O₃ (8YSZ) powder. The effect of the binder (carboxymethyl cellulose, CMC) ratio on the properties of the composite agglomerated powder was investigated with the aid of a laser particle size tester, scanning electron microscopy (SEM) and incidental energy spectrometry (EDS). A CYSZ thermal barrier coating with a columnar structure was prepared by PS-PVD, and EDS analysis of the coating cross-section and surface was carried out. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to analyze the physical phases of the coating. The results show that agglomerated powder with high sphericity, good flowability and uniform particle size distribution can be obtained with a binder ratio of 2%, the prepared coating has a uniform distribution of Ce element, and the coating phase is basically a t-phase structure, in which Ce⁴⁺ replaces Zr⁴⁺ and enters into the ZrO₂ lattice to form a homogeneous solid solution structure, showing the inhibition of the transition from t-phase to m-phase by CeO₂ doping. In addition, the prepared CYSZ coating remained intact after 100 cycles of water cooling at 1100 °C, showing high thermal shock resistance.

Thermal barrier coatings (TBCs) are deposited on metallic components to prevent heat flux due to their excellent thermal insulation function. Nowadays, TBCs have become the key core technology of the new generation gas turbines. TBCs prepared by plasma spraying method are more readily to be failed, which negatively affect the thermal insulation and may cause substrate erosion. Therefore, long life span is an important guarantee for TBCs to achieve thermal barrier function. This paper described the failure mechanism of plasma sprayed TBCs and crack-resistant designs. To begin with, the essential characteristics of plasma sprayed TBCs were revealed. Plasma sprayed TBCs appeared to be lamellar structure with connected 2D pores. As a result, the plasma sprayed TBCs have excellent thermal insulation and strain tolerance at as-deposited state. By thermal exposure, the density of 2D pores is decreased significantly, which dominantly account for the degradation of strain tolerance and thermal insulation. Subsequently, the failure mechanism of plasma sprayed TBCs is revealed. The degradation of strain tolerance leads to increase of driving force for cracking. Consequently, the micro-scale cracks are extended and connected to form large-scale cracks, which is responsible for the failure of plasma sprayed TBCs. Finally, cracking-resistant designs are reviewed from two aspects: decreasing driving force and increasing fracture toughness. It is worth noting that the current cracking-resistant design often has poor performance on thermal insulation. In future research, how to ensure high thermal insulation and long life of the coating while considering the economy is the key direction of the development of a new generation of high-performance thermal barrier coatings.

With the increase of the turbine inlet temperature of gas engines, the widely used Y₂O₃ partially stabilized ZrO₂（YSZ）thermal barrier coatings (TBCs) have been unable to meet the requirements, and new generation TBCs that can survive ultra high-temperatures are urgently needed. Among many TBC candidates, GdPO₄ has a great application prospect. In this study, GdPO₄/YSZ TBCs were prepared by air plasma spraying, and the effects of preparation parameters, especially spraying power on the phase composition, surface morphology, microstructure and bond strength of GdPO₄ coatings were investigated. The results show that the P loss takes place during spraying, and both GdPO₄ and Gd₃PO₇ phases are detectable in the final topcoats, the content of the latter decreases by reducing the spraying power. The GdPO₄ coating microstructure is mainly composed of piles of fully melted spray particles, among which there is porous micro-zone consisting of unmelted particles. With the decrease of the spraying power, the content of the micro-zone increases, and the coating thickness significantly decreases. The bonding strength of GdPO₄/YSZ TBCs decreases with the decrease of spraying power, which is mainly because the cohesion of coating decreases with the increase of unmelted micro-zone. Therefore, low spraying power is not beneficial to the coating bonding strength.

Advanced thermal barrier coatings (TBCs) have attracted extensive attention in the field of advanced aero-engine. The thermal cycling life and failure behavior of advanced TBCs still remain a challenge. This work focuses on crystal structure, microstructure and failure behavior of the LaZrCeO/YSZ double ceramic layers TBCs. A composite of pyrochlore and fluorite is formed in LaZrCeO/YSZ coating. The microstructure of LaZrCeO/YSZ coating is composed of feathery nanostructure and intra-columnar pores. The LaZrCeO/YSZ DCL TBCs exhibit good thermal cycling life at 1100 °C. After thermal cycling test, the cracks initiated and propagated in TGO layer due to the stress concentration, including horizontal cracks and vertical cracks, led to the instability of the whole coating system, and finally caused the failure of TBCs.