Abstract
Ytterbium monosilicate (Yb2SiO5) has been recognized as environmental barrier coatings (EBCs) material with potential applications for SiCf/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 Yb2SiO5 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 Yb2SiO5 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 (Ca3Yb2(SiO4)3), garnet and two kinds of apatite (Ca2Yb8(SiO4)6O2 and Ca4Yb6(SiO4)6O), whereas the CMAS melts with the lowest Ca/Si ratio is expected to form Yb2Si2O7 phase. With the Ca/Si ratio increasing, the viscosity of CMAS decreased and the aggressiveness of CMAS to Yb2SiO5 coating increased.
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