Cyclic oxidation and water vapor corrosion behaviors of multi-layer environmental barrier coatings with HfO2-Si bond coat for SiCf/SiC

Abstract

A novel multi-layer HfO2-Si/YbSi1.5/Yb2SiO5/LaMgAl11O19 environmental barrier coatings (EBCs) was prepared using atmospheric plasma spraying method to restrain spallation failure and improve lifetimes of coating. The thermal cycling behaviors of SiCf/SiC completely covered with multi-layer EBCs were comparatively investigated at 1300 °C and 1350 °C in air. Meanwhile the water vapor corrosion behavior of coated sample was also investigated at 1300 °C for 100 h in 90% H2O-10% O2 steam. The coating at 1300 °C showed better thermal shock resistance than the coating at 1350 °C, due to the increase of tensile stresses at 1350 °C. The coating showed different forms of crack penetration due to the influence of thermal cycling temperature and water vapor. The formation of HfSiO4 phase thanks to solid-state reaction between HfO2 and SiO2 alleviate the β→α-cristobalite phase change and avoid the crack initiation. However, the thermal mismatch stress was contributed to the spallation of coating along the surface of the SiCf/SiC substrate.