Thermal barrier coatings (TBCs) can provide thermal protection for high-temperature parts such as aeroengine, which is of great significance to improve its service life. In recent years, the thermal resistance requirements of the TBCs are constantly improving with the rapid development of the aeroengine. After a long thermal cycles, traditional TBCs are prone to crack and peel, which directly affects the safety and reliability of the aeroengine. As we all known, 8YSZ coatings have excellent thermal shock resistance and thermal insulation performance. However, the thermal oxidation and corrosion resistance of 8YSZ coatings still have great room for improvement due to the formation of many voids and defects during spraying process. As a common ceramic coating material, Al2O3 has high compactness and excellent mechanical properties, but its thermal expansion coefficient is too small to be used as TBCs alone. It can be found that the properties of 8YSZ and Al2O3 are complementary. Based on the perfor-mance advantages of each other, researchers began to introduce Al2O3 into 8YSZ to prepare 8YSZ-Al2O3 composite coatings to exploring the feasibility of using the composite coatings as the candidate for TBCs. The results show that the addition of Al2O3 results in the formation of amorphous phase in 8YSZ-Al2O3 composite coatings. The content of amorphous phase and its recrystallization are closely related to the thermal resistance of coatings. With the increase of Al2O3 content, the microstructure of the composite coatings becomes more compact, the young's modulus and hardness also show an increasing trend. Thus, Al2O3 can effectively adjust the microstructure and mechanical properties of 8YSZ coatings. As a result, the thermal oxidation and corrosion resistance of the composite coatings are obviously improved compared with the 8YSZ coatings, but its thermal cycle resistance still needs to be further optimized. In this paper, the research progress of the 8YSZ-Al2O3 composite coatings are mainly introduced according to the order of microstructure, mechanical properties, preparation process and high-temperature applications. The main advantages and disadvantages of the composite coatings compared with traditional 8YSZ coatings are described, and its future development trend is also prospected. © 2021, Materials Review Magazine. All right reserved.
