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.