The performance of a thermal barrier coating is influenced by the high temperature oxidation behavior of bond coat. In this paper, NiCoCrAlTaY bond coat was deposited by high velocity air-fuel (HVAF) spraying, and the microstructure and surface morphology of the bond coat before and after oxidation were examined. Results show that the HVAF sprayed NiCoCrAlTaY coating presented a dense microstructure and some partially melted particles in a near spherical morphology were deposited on the coating surface. A uniform α-Al2O3 oxide was formed on the HVAF sprayed MCrAlY coating surface after the pre-oxidation treatment in an argon atmosphere. A small fraction of nodular-shaped mixed oxides was formed when the MCrAlY coating was oxidized at 1000°C for 100 h. The amount of the mixed oxides did not significantly increase after 200 h oxidation. The large particles on the bond coat surface maintained homogeneous α-Al2O3 oxide scale in 200 h oxidation at 1000°C in air. A model is proposed to explain the formation of nodular-shaped mixed oxides.

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