Interdiffusion performance and oxidation behaviours of NiCrAlY/Al coatings on γ-TiAl

The interdiffusion behaviours and oxidation resistance of the NiCrAlY/Al duplex coated specimens during the isothermal oxidation test at 950°C were investigated. It was shown that the NiCrAlY coating system with an Al bondcoat outperformed the NiCrAlY single coating system and the substrate γ-TiAl alloy during hot exposure. Analysis techniques such as X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to study the phase formation, microstructure and depth distribution of the elements in the coated specimens. The results showed that the NiCrAlY/Al duplex coating system exhibited better oxidation resistance and adhesion strength with the substrate during scratch test. The SEM-EDS profile analyses further showed that the outward Ti diffusion and the inward Ni diffusion were delayed apparently by the Al interlayer, which was also considered as Al source for forming protective α-Al 2 O 3 scale on the NiCrAlY/Al coating surface.