Environmental Barrier Coatings (EBCs) for Ceramic Matrix Composites

With the rapid improvement of thrust-to-weight ratio of aeroengine, the internal temperature of aeroengine also gradually increases. Ceramic matrix composites (CMCs) react with water vapor and various molten salt impurities in the gas combustion environments, causing the rapid consumption of CMCs. To solve this problem, it is necessary to prepare the environmental barrier coatings (EBCs) on the surface of CMCs. To date, EBCs have experienced three generations of development. The first generation is a double-layer structure with mullite as the bonding layer and YSZ (7 wt.%) as the ceramic layer. The YSZ surface layer has an unavoidable penetrating crack due to the large difference in thermal expansion coefficient between the CMCs and YSZ. The second generation is a multi-layer structure coating with silicon and mullite as the bonding layer and BaxSr1-xAl2Si2O8 (BSAS) as the ceramic layer. However, they can only be used below 1300 °C due to the poor chemical stability. As the third generation of EBCs materials, rare earth silicate ceramics have attracted the attention owing to their high melting point, excellent high-temperature phase stability, and corrosion resistance. Therefore, the selection and development of high-performance EBCs materials has become the top priority in the field of EBCs.