Abstract
In this study, thermal barrier coating (TBC) of Y4Hf3O12 compound was produced by the plasma spray method. Phase composition, microstructure, thermophysical properties, high temperature stability, as well as CaO-MgO-Al2O3-SiO2 (CMAS) corrosion behaviour were investigated for Y4Hf3O12 coating. Results reveal Y4Hf3O12 coating of defective fluorite structure, as a result of high concentration of Y cation, to exhibit low thermal conductivity, outstanding structure stability up to 1300 °C and super good protectiveness against CMAS, but with relative low TEC. Preliminary findings support that Y4Hf3O12 ceramic can be top-layer materials on YSZ to form a double-ceramic-layer (DCL) TBC system. Thus, by adding a YSZ buffer layer, the Y4Hf3O12/YSZ DCL TBC was further developed on Ni-based superalloy and its thermal cycling durability was evaluated. It indicates that this DCL TBC system could undertake a cyclic lifetime longest to ~459 cycles. The failure behaviour in thermal shock test is related to the crack evolution induced by a combination of TEC mismatch, TGO growth and sintering of top-layer Y4Hf3O12.
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