The mechanical and thermal properties, CMAS corrosion resistance, and the wettability of novel thermal barrier material GdTaO4

Abstract

Because the CMAS corrosion and phase transformation at elevated temperatures above 1250 °C have limited the applications of traditional YSZ, the design of novel thermal barrier materials is a hotspot. GdTaO4 is considered as a type of potential novel thermal barrier material owing to its low thermal conductivity. In this study, the mechanical and thermal properties, CMAS corrosion resistance, and the wettability of the GdTaO4 were studied and compared with that of YSZ. The results show that the coefficient of thermal expansion and hardness of GdTaO4 are 14.1 × 10−6 K−1 (1350 °C) and 534.2 Hv0.3 respectively. The thickness of CMAS reaction layer of GdTaO4 is ~30.8 μm after 24 h reaction at 1350 °C, which is thinner than that of YSZ. After corrosion reaction, the CMAS glass aggregated instead of completely disappearing or continuously extending over the surface of GdTaO4. The main reaction product is Ca2Ta2O7, and the anorthite phase may not be detected, which is similar to YTaO4. By comparison, the dense substrate of YSZ became porous and CMAS glass has disappeared after 10 h. CMAS corrosion at 1350 °C. The on-line contact angle results show that the wettability of CMAS on GdTaO4 is worse than that on YSZ at 1350 °C, while the opposite of the work of adhesion, which indicates that GdTaO4 can remove liquid CMAS more easily than YSZ TBCs during the service. Furthermore, the corrosion depth and areas of GdTaO4 are smaller than those of YSZ in the same situation. These findings suggest that GdTaO4 possesses better high-temperature properties and CMAS corrosion resistance than YSZ as a kind of potential of thermal barrier material.