Advances in the Research of Surface Modification on the Resistance of Thermal Barrier Coatings to CMAS Corrosion

Thermal Barrier Coatings (TBCs) are utilized in aero-engines to reduce the temperature of hot-end components and offer mechanical and chemical protection. However, as engine service temperature rises, TBCs will be corroded due to the introduction of siliceous mineral fragments such as sand, dust, and volcanic ash composed predominantly of CaO, MgO, Al2O3, and SiO2 (CMAS). This corrosion can pose a potential hazard and jeopardize the safety of aero-engine hot-end components. To ensure the safe operation of aero-engines, it is essential to addressing this issue. Surface modification is one potentially effective method that can enhance the CMAS corrosion resistance of TBCs. This method can prevent the adhesion of molten CMAS to the coating surface, as well as hinder the infiltration and reaction of molten CMAS by creating physical barriers or chemical sacrificial layers. Surface modification technologies can consist of four categories based on their principles of mechanical, physical, chemical, and electrochemical surface modification technologies. Each category has its unique advantages and disadvantages, which are briefly outlined in the present study. Physical surface modification is a modification method that does not result in a chemical reaction on the surface of the material. This method can construct a protective layer on the surface of the material, including physical vapor deposition, laser surface modification, and intense pulsed electron beam surface modification. Chemical surface modification technology mainly includes two modification methods of sol-gel method and chemical vapor deposition. Modifying the surface composition, organization, and morphology of the material through atomic diffusion, chemical reaction, and other means, improves the surface properties of the material. Electrophoretic deposition is a type of electrochemical surface modification technology. The recent research progress in surface modification technologies for thermal barrier coatings is summarized and the design studies of new thermal barrier coatings are guided to improve the microstructure and reduce defects of thermal barrier coatings, achieving the purpose of enhancing the corrosion resistance of CMAS. Coating surface modification technologies have limitations such as thickness limitations, coating bonding issues, temperature limitations, and coating consistency that need to be overcome and improved in practice. As the temperature of aero-engines increases in the future, the requirements for surface properties will also increase. Traditional experimental methods are costly and inefficient, while computational simulation can predict and model the properties and structure of materials, reducing costs and increasing efficiency. The research progress of first-principles calculations and finite-element simulations on new thermal barrier-coated ceramic materials such as rare-earth oxide-doped yttrium oxide-stabilized zirconia, rare-earth zirconate, rare-earth tantalate, and chalcocite is discussed to fully understand the evolution of the coating microstructures and the interfacial structures. In future research, new materials and additional surface modification technologies will be explored for applications in high/ultra-high temperature environments. The emergence of these new coatings provides innovative ideas for improving and enhancing the performance of ultrahigh-temperature thermal protection, and will greatly promote the development and progress of China's high-temperature/ultrahigh-temperature field. In conclusion, by utilizing surface modification technologies and exploring new materials, it can guarantee the safety and reliability of aero-engines in high/ultra-high temperature environments. Therefore, investing in research and development to further improve the performance and reliability of TBCs is essential. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.