Isothermal oxidation behaviour of a gradient NiCoCrAlSiY coating deposited by arc ion plating on a Ni-based single crystal superalloy

A gradient NiCoCrAlSiY coating consisting of Al-enriched outer zone and Cr-enriched internal zone was prepared using arc ion plating method and subsequent annealing treatment. Isothermal oxidations were performed at 1000 °C and 1100 °C in static air. The results confirmed an enhanced performance for the gradient NiCoCrAlSiY coating in contrast to the conventional NiCoCrAlSiY, due to the high-Al content and the in-situ Cr(Re, W)-rich diffusion barrier which exists in the gradient coating. The degradation mechanisms for the two coatings and the formation mechanism for the diffusion barrier are discussed.