Abradable ytterbium disilicate environmental barrier coatings: A study of steam, CMAS and combined steam-CMAS corrosion
A. Lynam, Buhao Zhang, Acacio Rincón Romero, Ebenezer B. Owusu, Fangfang Xu, Gyn Brewster, G. Pattinson, Tanvir Hussain
Abstract
Abradable environmental barrier coatings (EBCs) are essential for improving gas turbine efficiency with ceramic matrix composites (CMCs). This study examined ytterbium disilicate (Yb 2 Si 2 O 7 or YbDS) abradable EBCs with 8 %, 15 %, and 22 % porosity, deposited via atmospheric plasma spraying . Coatings were exposed to steam, CMAS, and combined steam-CMAS at 1350 °C for 100 hr. Results showed that porosity had minimal impact on corrosion resistance . Steam exposure formed a thin ytterbium monosilicate (Yb 2 SiO 5 or YbMS) layer, while CMAS caused dissolution-precipitation, forming reprecipitated Yb 2 Si 2 O 7 and Yb-apatite (Ca 2 Yb 8 (SiO 4 ) 6 O 2 ). Combined exposure increased CMAS penetration depth by 25 %, enhanced Yb-apatite formation, and introduced ytterbium aluminium garnet (Yb 3 Al 5 O 12 , YbAG). These findings demonstrate that the interaction of CMAS and steam accelerates coating degradation, highlighting the need for optimized phase composition and microstructure to enhance abradable EBC durability under turbine-relevant conditions.