CMAS环境下热障涂层的损伤机理及防护策略

With the trend of higher thrust-weight ratio and thermal efficiency of aero-engine, the turbine inlet temperature increases significantly. Thermal Barrier Coatings (TBCs) of aeroengine blades are increasingly corroded by environmental deposits such as volcanic ash, fly ash, runway debris, industrial smoke, automobile exhaust and PM2.5 during the high-temperature service. The chemical composition of the silicate ash is mostly CaO-MgO-Al₂O₃-SiO₂ (CMAS), and their melting point is about 1 240℃, which is far lower than the service temperature of aeroengine. Once sucked into aero-engine at such high temperature, CMAS can rapidly molten and infiltrates into the TBCs structure. On the one hand, CMAS causes physical impact and damage on the TBCs surface, and the molten CMAS tends to cause blocking of cooling holes in turbine blades, which results in decrease of cooling efficiency, change of temperature and stress distribution in blades. On the other hand, the molten CMAS chemically reacts with the blade coatings, resulting in corrosion spallation and premature failure of TBCs. The durability of TBCs is significantly reduced due to the CMAS deposition. It is very important to make the protection strategy to constrain the adherence and corrosion of molten CMAS on TBCs at high temperature to ensure the development of advanced aero-engine. Besides, mastering the physical and chemical properties of CMAS in different environments is the basis for developing CMAS-resistant TBCs. This paper focuses on the summary of the composition and rheological properties of CMAS and the thermo-chemical and thermo-mechanical failure mechanism of TBCs in CMAS environment. And the solutions to CMAS, such as coating structure optimization, adding permeability barrier layer and sacrificial layer are briefly overviewed.