Water vapor corrosion behaviours of nanostructured Yb₂O₃-Yb₂SiO₅/mullite/Si environmental barrier coatings

In this work, the nanostructured Yb₂O₃-Yb₂SiO₅/mullite/Si environmental barrier coatings (EBCs) were designed and prepared by atmospheric plasma spraying. The water vapor corrosion behavior of coatings was investigated at a temperature of 1350 °C for durations ranging from 100 to 500 h, and the influence of phase compositions, microstructure on this behavior was systematically investigated. The results indicate that phase transformation occurs during the water vapor corrosion process, and severe corrosion takes place at the Yb₂O₃-Yb₂SiO₅ top coating and the mullite intermediate layer. Obvious diffusion reaction between Yb₂O₃-Yb₂SiO₅ and mullite layers occurred without water vapor, while the diffusion reaction cannot be observed under water vapor. The water vapor corrosion mechanism of EBCs is mainly attributed to residual thermal mismatch stresses, phase transformation resulting from sintering of Yb₂O₃-Yb₂SiO₅, as well as the formation of TGO by oxidation.