Thermal barrier coating (TBC) materials play an important role in protecting the superalloy base from oxidation and corrosion, and reducing the operation temperature of the speralloys in the thermal protection of aero engine and gas turbine. There are many high entropy rare earth oxides in the new thermal barrier coating materials, which can achieve better thermal, mechanical, high-temperature phase stability, sintering resistance, corrosion resistance and other properties than the single principal component rare earth oxides. However, the research on high-entropy rare earth oxides is still in the preliminary stage at present. Especially, the role of rare earth elements on material properties has not been fully defined, and no unified standard has been formed. In this paper, the basic structure of thermal barrier coating was briefly reviewed, and the crystal structure, thermophysical and mechanical properties of five high entropy rare earth salts such as high entropy zirconate, cerate, hafniate, tantalate and niobate were emphatically summarized. In addition, the differences between those salts and the corresponding single component of rare earth salts were compared and analyzed, and many factors affecting their performance were discussed. Compared with single component rare earth oxides, the thermal conductivity, thermal expansion coefficient and phase stability of high entropy rare earth oxides were significantly improved. Finally, the future development direction of high entropy rare earth thermal barrier coatings was prospected.

Due to their excellent high-temperature strength, good processing plasticity and corrosion resistance, refractory metals and their alloys are extensively utilized in the aviation, aerospace and nuclear industries, serving as important high-temperature structural materials. However, their susceptibility to oxidation often causes serious oxidation before reaching service temperatures, leading to rapid failure. High performance high-temperature protective coatings are essential for maintaining the performance of these refractory alloy materials at present. However, the actual service conditions of high-temperature protective coatings on surfaces of refractory metals and their alloy are very harsh, often accompanied by strong thermal shock, which is an important reason for coating failure. Therefore, a high-temperature protective coating on refractory metals must have excellent constant temperature oxidation resistance and good thermal shock resistance. In this paper, the thermal shock failure mechanism of high-temperature protective coatings on the surfaces of refractory metals was reviewed, and the key parameters affecting the coatings’ thermal shock resistance were discussed. The research status of the thermal shock resistance of three main coating systems, including silicides, metals and composite coatings on the surface of refractory metals, was expounded. Additionally, the modification methods and their improvement effects, such as optimizing the coating structure, adding ceramic particles and designing composite coatings to improve the thermal shock resistance of coatings, were reviewed. Finally, the future development direction of high-temperature protective coatings for refractory metals was prospected from three aspects: reducing the mismatch of thermal expansion coefficient between the coating and the substrate, improving the interface bonding performance between the substrate and coating and designing composite gradient coatings.

Thermal barrier coatings (TBC) are used for thermal protection of aero-engine turbine blade surface, which mainly consist of bond coatings and ceramic coatings. Accurate measurement of temperature distribution on the surface of ceramic coating and bond coating/ceramic coating interface is of great significance for guiding the design and preparation of high-heat insulation structure of coating. At present, the surface temperature can be measured by the existing non-contact and contact temperature measurement technologies, and the interface temperature can be measured by the contact temperature measurement technology. In this paper, three kinds of technologies applied to the turbine blade surface temperature measurement of aeroengine were introduced. Among them, the thermal barrier coating surface temperature measurement technologies included infrared radiation, fluorescence, crystal and optical fiber, which based on the optical principle, and temperature indicating paint temperature measurement, which based on thermotropic principle. Moreover, the temperature measurement technologies of landfill thermocouple and film thermocouple based on thermoelectric principle were applied to the temperature measurements of thermal barrier coating interface, and their principle, advantages and limitations were introduced. Furthermore, the thermal insulation mechanism and performance optimization of thermal barrier coating were introduced, and the temperature measurement technology of thermal barrier coating surface or interface and the direction of coating structure designs were prospected.

For further enhancing the hot corrosion resistance of the NiCrAlY coating, the NiCrAlY/NiAl/Al coating(coating A) and the NiCrAlY/Pt/NiAl/Al coating(coating B) were deposited on the surface of DZ125 alloy by arc ion plating technology, and then the gradient coating structure with gradually changing composition was formed by vacuum diffusion annealing. The modified element Pt was introduced into the coating to enhance the hot corrosion resistance of the coating, and the hot corrosion behavior of two coating systems in different mixed salts at 900 ℃ was studied. Additionally, the microstructure, phase composition and element distribution of the coating after hot corrosion were analyzed by SEM, EDS, XRD and EPMA. Results showed in a mixed salt of K₂SO₄ + Na₂SO₄ at 900 ℃, the extensive spalling of the oxide film occurred on the surface of coating A. Pt in coating B inhibited the segregation of S at the coating/oxide film interface, and enhanced the adhesion of the oxide film. In the mixed salt of NaCl + Na₂SO₄ at 900 ℃, the Cr element and O element of coating A underwent outward diffusion and inward diffusion, respectively. The outward diffusion of Cr was easy to react with S to form a harmful phase Cr_xS_y. In contrast, the Pt in coating B inhibited the outward diffusion and inward diffusion of Cr and O elements. Overall, the addition of Pt layer between NiCrAlY and NiAl layers significantly enhanced the hot corrosion resistance of the NiCrAlY coating in mixed salts.

The composite components of ceramic matrix face serious water oxygen corrosion degradation in the aeroengine gas environment. The application of environmental barrier coatings on the surface of components for thermal protection is an effective measure to improve the high-temperature performance and extend the service life of ceramic matrix composite components. The high-temperature stability of the environmental barrier coatings plays a significant role on the structural integrity of the components. For elucidating the failure behavior and mechanism of environmental barrier coatings subjected to high-temperature water oxygen corrosion, this work conducted a static high temperature water oxygen corrosion experiment on an atmospheric plasma spraying Yb₂Si₂O₇/mullite/silicon environmental barrier coating system at 1 350 ℃ and 90%(volume fraction) H₂O-10%O₂ water/oxygen vapor environment. Meanwhile, XRD, SEM, EDS and other material characterization analysis methods were employed to study the failure behavior of coatings in high-temperature static water oxygen corrosion environments, and obtain the evolution mechanisms of the microstructure and physical phases of EBCs coatings during the corrosion process. The failure mechanism of EBCs coatings was revealed. Results showed that Yb₂Si₂O₇ on the surface reacted with oxidants(mainly water) in the environment to generate volatile substances Si(OH)₄, leading to the continuous consumption of Yb₂Si₂O₇. The silicon element in the mullite layer inter-diffused with the rare earth element in the Yb₂Si₂O₇ layer, making the process and mechanism of high-temperature chemical reactions extremely complex. After 500 h of corrosion, the coating experienced bulging and detachment, resulting in the coating failure.

With the continuous development of aero engines in the direction of high thrust-to-weight ratio and high performance, traditional and single thermal barrier coatings(TBCs) have been unable to meet the harsh service requirements of hot-end components. Lanthanum zirconate(La₂Zr₂O₇) has the advantages of high melting point, structural stability at high temperatures, low thermal conductivity and excellent thermal insulation performance, making it an excellent candidate material for the next generation of TBCs. However, there are still two key issues in practical applications, namely low thermal expansion coefficient and poor fracture toughness. Consequently, La₂Zr₂O₇ materials during service may experience localized thermal stress concentration due to thermal mismatch, leading to premature peeling and failure of the coating and seriously affecting the service life of the coating. Domestic and foreign researches have shown that modification of La₂Zr₂O₇ materials can effectively solve the above problems. Therefore, this article systematically analyzed the researches on the modification of La₂Zr₂O₇ materials, and summarized them into four categories: second-phase composite, rare earth doping, nanoization and high-entropy. The article focused on the impact and toughening mechanism of the four different modification methods on the thermal conductivity and thermal expansion coefficient of La₂Zr₂O₇ materials. Furthermore, the research works on La₂Zr₂O₇ material modification were summarized and prospected, which could provide the theoretical support for the application of La₂Zr₂O₇ material in the field of thermal barrier coatings.