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

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 & DEG;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 & beta;-cristobalite to & alpha;-phase, crystallization of amorphous SiO2 also caused volume change, inducing longitudinal cracks through the TGO layer, which may lead to the failure of EBCs.