Robust corrosion resistance of Yb4Hf3O12 coating against CMAS attack at 1300-1500 °C

With the continuous evolution of service temperature, corrosion of molten calcium-magnesium-aluminumsilicate (CMAS) deposits has been identified as a major obstacle to the application of thermal/environmental barrier coatings (T/EBCs). This study investigated the CMAS corrosion behaviors and mechanisms of plasmasprayed Yb4Hf3O12 coatings, a promising candidate for T/EBCs, at 1300, 1400 and 1500 degrees C. Results showed that Yb4Hf3O12 coating can effectively withstand CMAS corrosion by producing crystalline products that consumed a significant amount of CMAS components. Temperatures exerted significant influence on the corrosion behaviors of the coating. At lower temperatures, corrosion was limited near the coating surface because of the slower reaction rate. The infiltration of CMAS melts increased sharply with rise temperature. However, the transformation of crystalline field from apatite to cuspidine at elevated temperatures effectively suppressed the further penetration. The result also indicated that the smaller RE3+ radius in Yb4Hf3O12 may contribute to the superior corrosion resistance.