Effect of Gd2O3 Addition on the Growth Behavior of the Dense Reaction Layer at the Interface Between Al2O3 Ceramic and CMAS at 1300 °C

The exploration of new materials with stable molten calcium–magnesium–aluminum-silicate (CMAS) resistance at elevated temperatures is of great significance to the development of advanced aero-engines. In the present study, Al2O3−xGd2O3 (x = 5, 10, 20, 30 mol.%) ceramic samples were prepared by the high-temperature solid-state synthesis method. The thermochemical reaction behavior, reaction products, and growth kinetics of the reaction layer for the ceramics with molten CMAS at 1300 °C were investigated. The results reveal that the primary reaction products between Al2O3−xGd2O3 ceramics and molten CMAS are anorthite (CaAl2Si2O8), gehlenite (Ca2Al(AlSi)O7), spinel (MgAl2O4), and Gd-apatite (Ca2Gd8(SiO4)6O2). In the initial reaction stage, a dense double-layer reaction layer composed of anorthite and spinel is formed at the ceramic/CMAS interface, while its growth rate decreases with increasing reaction time. Increasing the Gd2O3 doping content inhibits the growth of the reaction layer and enhances the CMAS penetration resistance of Al2O3−xGd2O3 ceramics. The mechanism is discussed systematically.