Reaction of Yb2SiO5 EBCs against CMAS melts with different composition.

Ytterbium monosilicate (Yb 2 SiO 5) has been recognized as environmental barrier coatings (EBCs) material with potential applications for SiC f /SiC. However, the corrosion caused by calcium-magnesium-alumino-silicate (CMAS) has posed significant challenges to the design and application of EBCs. In this study, reaction of Yb 2 SiO 5 EBCs against CMAS melts with different Ca/Si ratios (1.1, 0.75, 0.64, and 0.42) at 1350 °C was investigated. Results showed that the components of CMAS have a significant impact on the corrosion behaviors of the Yb 2 SiO 5 coating. The difference in Ca/Si ratio of CMAS changes the phase equilibrium during the reaction process. The CMAS melts with the highest Ca/Si ratios can form a combination of silico-carnotite (Ca 3 Yb 2 (SiO 4) 3), garnet and two kinds of apatite (Ca 2 Yb 8 (SiO 4) 6 O 2 and Ca 4 Yb 6 (SiO 4) 6 O), whereas the CMAS melts with the lowest Ca/Si ratio is expected to form Yb 2 Si 2 O 7 phase. With the Ca/Si ratio increasing, the viscosity of CMAS decreased and the aggressiveness of CMAS to Yb 2 SiO 5 coating increased. [ABSTRACT FROM AUTHOR]