Comprehensive study of the effect of Hf and Ta co-doped MCrAlY bond coat on the high-temperature properties of thermal barrier coating

The MCrAlY bond coat is modified by reactive element (RE) Hf and refractory element Ta, and the high-temperature oxidation resistance of the thermal barrier coating (TBC) before and after the modification are investigated by comparative experiments. The experiments use high-velocity oxygen-fuel (HVOF) to prepare NiCoCrAlY and NiCoCrAlYHfTa bond coats on the surface of GH4099 high-temperature alloy, and then yttrium stabilized zirconia (YSZ) ceramic layers are prepared on the surface of the bond coat by atmospheric plasma spraying (APS), and cyclic oxidation is carried out in air at 1050 ℃ until failure. It is shown that the oxidation lifetime of the modified TBC reached 1992 h, which is one time higher than that of the unmodified TBC. The doping of Hf and Ta elements reduces the growth rate of the oxide layer, and these diffuse externally and combine with the internally diffused O to form HfO2 and Ta2O5 in the thermally grown oxide (TGO) layer, thereby improving the adhesion and mechanical properties of the oxide layer. In addition, the bonding strength and thermal shock resistance of the TBCs are significantly improved after doping with Hf and Ta elements, which prolongs the lifetimes of the TBCs. In this paper, the morphology, structure, and properties of the modified TBCs are characterized to investigate the mechanism of the oxidation lifetime extension.