High Temperature Oxidation Resistance of NiCrAlY Coating on Surface of TiAl Alloy

A NiCrAlY coating was deposited on the surface of γ-TiAl alloy by multi-arc ion plating (MAIP). The morphology, microstructure and phase composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The oxidation kinetic curves of the substrate and coating were obtained by oxidation at constant temperature. Results indicate that a layer of protective oxide film forming on the coating at high temperature could significantly improve the oxidation resistance of TiAl alloy. Mutual diffusion of Ni, Ti elements happened at 650-950 ℃. A diffusion zone and dentate TiNi phase between the coating and the substrate were found at 850 ℃, then at 950 ℃ the phenomenon of mutual diffusion aggravated, TiO2 generated on the coating surface, which resulted in Kirkendall pores at the interface between the coating oxide film and the substrate. This was not benifical to improve the high temperature oxidation resistance.