Mechanical properties and calcium-magnesium-alumino-silicate (CMAS) corrosion behavior of a promising Hf6Ta2O17 ceramic for thermal barrier coatings

Hf6Ta2O17 ceramics are successfully prepared by solid state reaction and pressureless sintering. The mechanical properties and the calcium-magnesium-alumino-silicate (CMAS) corrosion behavior of Hf6Ta2O17 ceramics are studied. The hardness, elastic modulus and fracture toughness of Hf6Ta2O17 ceramics are 18.45 GPa, 273.42 GPa and 2.6–3.1 MPa m1/2, respectively. As the Hf6Ta2O17 ceramics are attacked by CMAS, the reaction layer and dense layer are formed on the ceramic surface, which prevents the further infiltration of molten CMAS. HfSiO4 and Ca2Hf7O16 are confirmed as the main reaction products of Hf6Ta2O17 and CMAS. Hf6Ta2O17 ceramics exhibit better CMAS corrosion resistance than 8 wt% yttria stabilized zirconia (8YSZ) ceramics, which is attributed to the dense structure formed by corrosion products (hafnium tantalum oxide and Ca2Hf7O16) and lower theoretical optical basicity (OB) value. Furthermore, Hf6Ta2O17/YSZ double ceramic top coat thermal barrier coatings (TBCs) are successfully prepared by plasma spraying, and the thermal cycling performance is investigated. Hf6Ta2O17/YSZ double-layers TBCs has good thermal cycling performance as 8YSZ single-layer TBCs.