Thermal cyclic oxidation and interdiffusion of NiCoCrAlYHf coating on a Ni-based single crystal superalloy

A NiCoCrAlYHf coating was deposited onto a third generation single crystal superalloy DD10 by arc ion plating (AIP). In the present study, thermal cyclic oxidation and interdiffusion of NiCoCrAlYHf coating at 1100 °Cwere investigated to 1000 h. The coating surface, interface morphology and phase structure of the organization were characterized by scanning electron microscopy (SEM), energy dispersion X ray spectroscopy (EDS) and X ray diffraction (XRD). An interdiffusion zone (IDZ) and a secondary reaction zone (SRZ) were formed after 300 h. Severe inward diffusion of Al, Co and Cr from NiCoCrAlYHf coating and outward diffusion of Ni and refractory elements such as Re and W from the superalloy occur at 1100 °C in air. The SRZ consisting of γ, γ′ and topologically closed-packed phase (TCP) was formed 60 μm distance from the surface of coating in the superalloy after 300 h oxidation. Additionally, the development of IDZ and growth of the SRZ was also observed during thermal cyclic oxidation. Subsequently, interdiffusion coefficients of Al were presented by using a modified form of the Boltzmann–Matano analysis. - Highlights: • NiCoCrAlYHf coating protect third generation Ni-based single crystal superalloy very well and improve oxidation-resistance property. • Interdiffusion zone and secondary reaction zone are formed during thermal cycling oxidation. • Outward diffusion of Ni, W and Re and inward diffusion of Al, Co and Cr promote the formation of secondary reaction zone. • The diffusion coefficient of Al increases slightly with the concentration of element Al in NiCoCrAlYHf coating when the temperature is constant. - Graphical abstract: According to the figure, it shows that an interdiffusion zone formed under NiCoCrAlYHf coating and a secondary reaction zone formed in third generation single crystal superalloy DD10.