Silicon‐based bond coatings for environmental barrier coatings: Present status and prospective

Abstract

Environmental barrier coatings (EBCs) are indispensable for the service of SiC‐based turbine engines. The Si‐bond coating is a critical layer that prevents oxidants from penetrating SiC substrates and determines the service lifetimes of EBCs. In this study, the oxidation behaviors and failure mechanisms of Si‐based bond coatings were reviewed. The large growth rate and phase transformation of thermally grown oxides (TGOs, SiO2) seriously deteriorate the service of Si‐bond coatings. The low melting point of Si further limits its application in next‐generation engines above 1 427°C. The results show that an isolated particle healing (IPH) treatment decreased the oxidation rate of the Si‐bond coating by ∼24% at 1 300°C. Moreover, the Si–HfO2 and Si‐stabilizer (Si–Al2O3 or Si‐mullite) composite/duplex bond coatings can eliminate SiO2 phase transitions, thus improving the service lifetime. In addition, rare earth silicide (RESi), SiC and SiO2–HfO2 composite show potential for use in next‐generation EBCs above 1 427°C. This review provides guidance for designing Si‐based bond coatings with improved service lifetime.