Calcium-magnesium-aluminosilicate corrosion behaviors of rare-earth disilicates at 1400 °C

Environmental barrier coatings (EBCs) are used to prevent oxidation of underlying ceramic matrix composite (CMC) structural components in gas turbines. When the siliceous minerals deposit on the surface of EBCs, a glassy melt of calcium-magnesium-aluminosilicate (CMAS) will be formed, leading to the EBCs degradation. In this study, seven rare-earth disilicates (RE2Si2O7, RE = Yb, Lu, La, Gd, Eu, Sc, and Y) were fabricated to analyze their CMAS corrosion behaviors. The results indicated that the RE2Si2O7 could react with the CMAS in the temperature range of 1250-1350 °C. Reaction zones formed at the interfaces. For the Yb2Si2O7, Lu2Si2O7, La2Si2O7, Eu2Si2O7 and Gd2Si2O7, the reaction zones dissolved into the molten CMAS and separated from the RE2Si2O7. As for the Sc2Si2O7 and Y2Si2O7, the reaction zones could stay at the interface. They could effectively block the molten CMAS to penetrate into the RE2Si2O7 and protect them from CMAS corrosion.