Research on water vapor/calcium-magnesium-aluminum-silicate corrosion failure behavior and mechanisms of Er-based rare earth silicate environmental barrier coating

To investigate the corrosion failure behavior and mechanism of environmental barrier coatings at high temperatures, coatings of Si-Yb₂Si₂O₇-Er₂SiO₅ system were prepared on continuous silicon carbide fiber-reinforced silicon carbide based ceramic matrix composites by atmospheric plasma spraying, and water oxygen corrosion and molten calcium-magnesium-aluminum-silicate corrosion assessment experiments were conducted at 1350 ℃. The failure behavior and the evolution of microstructure and phase composition of the EBCs during corrosion were studied by XRD、SEM、EDS. The results showed that in water vapor corrosion, Er₃Al₅O₁₂ and Er(OH)₃ generated by the reaction of Er₂SiO₅ with H₂O and Al(OH)₃ increased continuously, the volatilization of Er(OH)₃ increased the coating porosity, promoting further infiltration of water vapor and internal corrosion. Meanwhile, the generated Er₃Al₅O₁₂ phase had a thermal expansion mismatch with the coating matrix, generating significant internal stress during thermal cycling. The coupling effect of chemical corrosion and physical stress ultimately led to the formation of longitudinal cracks throughout the entire coating, resulting in coating failure; In CMAS corrosion, Er₂SiO₅ reacts with CMAS to form apatite and garnet phases, which hinder the infiltration of CMAS melt. However, due to the mismatch between the product and the thermal expansion coefficient of the coating, longitudinal cracks appeared in the coating, but the coating structure remained intact and did not peel off.