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

Abstract Yb 2 SiO 5 and Yb 2 Si 2 O 7 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 Yb 2 SiO 5 , Yb 2 Si 2 O 7 coatings and Yb 2 SiO 5 /Yb 2 Si 2 O 7 /Si, Yb 2 SiO 5 /Si EBCs were subjected to steam with alumina at 1400°C for 200 h. Results showed that Yb 3 Al 5 O 12 reaction layer and Yb 2 SiO 5 corrosion layer were formed on the Yb2SiO5 coating, while porous Yb 2 SiO 5 corrosion layer with Yb 3 Al 5 O 12 phase was formed on the Yb 2 Si 2 O 7 coating. By designing Yb 2 Si 2 O 7 as intermediate layer, the corrosion resistance of Yb 2 SiO 5 /Yb 2 Si 2 O 7 /Si EBCs was significantly improved. In addition to phase transition of β‐cristobalite to α‐phase, crystallization of amorphous SiO 2 also caused volume change, inducing longitudinal cracks through the TGO layer, which may lead to the failure of EBCs.