High-temperature performance of thermal environmental barrier coatings in 90%H2O-10%O2 conditions at 1475 °C

The performance of 50HfO2-50SiO2/YxYb(2−x)Si2O7 thermal environmental barrier coating prepared using atmospheric plasma spraying was investigated in the Al2O3 tube furnace in 90%H2O-10%O2 conditions at 1475 °C. The results showed that YxYb(2−x)Si2O7 layer was contaminated by alumina impurities during the testing process. The thermally grown oxide layer was formed at the bond coat/SiC interface, it grew as the cycles increased. Furthermore, the (Y/Yb)2O3-HfO2 solid solution with a higher coefficient of thermal expansion was formed at YxYb(2−x)Si2O7/50HfO2-50SiO2 interface. The horizontal cracks were the principal factor that caused the failure of 50HfO2-50SiO2/YxYb(2−x)Si2O7. 50HfO2-50SiO2/YxYb(2−x)Si2O7 protected SiC for 25 cycles in steam conditions.