Microstructure and oxidation behaviour of plasma-sprayed NiCoCrAlY coatings with and without Ta on Ti44Al6Nb1Cr alloys

NiCoCrAlY coatings with and without Ta were plasma-sprayed onto Ti44Al6Nb1Cr alloy to investigate their microstructure and oxidation resistance at 900 °C for 100 h. The results indicated that the oxidation resistance of the NiCoCrAlY coating was better than that of the NiCoCrAlYTa coating. The formation of Al2O3 scale on the NiCoCrAlYTa coating was inhibited due to the low Al concentration and the dragging effect of Ta. Furthermore, loose NiO/CoO scale on the NiCoCrAlYTa coating promoted the inward diffusion of oxygen. As a result, an Al2O3 layer was formed at the interface, suppressing interdiffusion between coating and substrate.