Corrosion behavior and mechanism of ytterbium silicates environmental barrier coatings subjected to thermal cycling in water vapor

Abstract

Yb₂SiO₅ and Yb₂Si₂O₇ have been considered to be promising environmental barrier coatings (EBCs) materials for silicon‐based ceramics. Besides the various requirements EBCs must satisfy, it must be resistant to severe corrosion by high‐temperature water vapor as well as CMAS. In this work, the Yb₂SiO₅, Yb₂Si₂O₇ coatings and Yb₂SiO₅/Yb₂Si₂O₇/Si, Yb₂SiO₅/Si EBCs were subjected to steam with alumina at 1400°C for 200 h. Results showed that Yb₃Al₅O₁₂ reaction layer and Yb₂SiO₅ corrosion layer were formed on the Yb2SiO5 coating, while porous Yb₂SiO₅ corrosion layer with Yb₃Al₅O₁₂ phase was formed on the Yb₂Si₂O₇ coating. By designing Yb₂Si₂O₇ as intermediate layer, the corrosion resistance of Yb₂SiO₅/Yb₂Si₂O₇/Si EBCs was significantly improved. In addition to phase transition of β‐cristobalite to α‐phase, crystallization of amorphous SiO₂ also caused volume change, inducing longitudinal cracks through the TGO layer, which may lead to the failure of EBCs.