Composition effects of La₂Ce₂O₇ thermal barrier coatings against calcium-magnesium-aluminum-silicate (CMAS) at 1250°C

The evaporation of both CeO₂ and La₂O₃ in high temperature plasma arc leads to deviation of plasma sprayed La₂Ce₂O₇ coating composition from the starting powder particle. Such change results in significantly inhomogeneity of compositions within a coating which influences the performance of calcium- magnesium-alumina-silicate (CMAS) corrosion. In this study, the pellets with different Ce / La ratio were interacted with molten CMAS glass. The penetration of molten CMAS on different pellets was characterized by scanning electron microscopy and energy dispersive spectrum (EDS) and the phase of different powder mixtures treated at 1250 °C was characterized by X-ray diffraction ( XRD ). The effects of pellets with different Ce / La ratio on the CMAS corrosion after thermal exposure at 1250 °C for 50 h were investigated. The result demonstrated that pellets with ratio of Ce / La greater than or equal to 1.0 were completely dissolved into the molten CMAS, at the same time the others were also damaged, forming diffusion layer and reacted layer, respectively. The difference of the ratio of Ce / La indeed affected their performance against CMAS attack.