Growth behavior and barrier mechanism of corrosion product layer from calcium-magnesium-aluminosilicate on Yb₂Si₂O₇-Yb₂SiO₅ composite environmental barrier coatings at 1300 ℃

The corrosion mechanism of Yb₂Si₂O₇-Yb₂SiO₅ composite environmental barrier coatings (EBCs) with various mass ratios under calcium-magnesium-aluminosilicate (CMAS) attack at 1300 ℃ for 100 h was investigated. The predominant products of the 75Yb₂Si₂O₇-25Yb₂SiO₅ (with a dense layer thickness of 15.83 ± 1.79 μm) and 50Yb₂Si₂O₇-50Yb₂SiO₅ (with a dense layer thickness of 11.61 ± 1.19 μm) EBCs are apatites with dense bottom structures. In addition to apatite, a garnet layer is produced on the 25Yb₂Si₂O₇-75Yb₂SiO₅ EBC surface due to the high Al:Si ratio in the CMAS melt. The dense corrosion product layer (∼35.37 ± 4.75 μm) on the 25Yb₂Si₂O₇-75Yb₂SiO₅ EBC obviously hindered the infiltration of the CMAS melt, showing superior CMAS corrosion resistance.