CaO–MgO–Al2O3–SiO2 熔体在钇稳定氧化锆上的润湿、铺展与界面反应

Abstract Yttria-stabilized zirconia (YSZ) is often used as a thermal barrier coating (TBC) material for gas turbines. When calcium-magnesium–aluminum-silicate (CMAS) deposits derived from sand, dust and volcanic ash accumulates on the TBC during operation, the molten CMAS wets and spreads, and reacts with the TBC leading to the formation of Y-depleted ZrO 2 , as a result, compromising the thermal protection of the TBC. In this study, the contact angles of CMAS melts on YSZ and Al 2 O 3 substrates were measured using the sessile drop method to observe the effects of interfacial reactions on the wetting and spreading behaviors of CMAS melts. To elucidate the thermodynamics of the formation of Y-depleted ZrO 2 in CMAS melts, the saturation solubility of ZrO 2 in four different CMAS melts was measured. Sessile drop measurements and electron probe microanalyzer observations revealed that the contact angles of CMAS melts on the YSZ substrates continuously decreased owing to the progress of interfacial reaction, leading to the formation of Y-depleted ZrO 2 . On the other hand, the contact angles of CMAS melts on the Al 2 O 3 substrates remained constant because anorthite covered the entire interface and the local equilibrium at the interface was reached. The ZrO 2 solubility measurements revealed that the reprecipitation of Y-depleted ZrO 2 is attributed to the reduction in the saturation solubility of ZrO 2 in the CMAS melts near the interface, resulting from a decrease in the CaO and MgO concentrations and an increase in the Y 2 O 3 concentration in the CMAS melt owing to the CMAS/YSZ interfacial reaction.