Cyclic oxidation and interdiffusion behavior of Ru/NiAlHf coating on Ni-based single crystal superalloy

A novel Ru/NiAlHf coating was deposited onto an Ni-based single crystal superalloy N5 by electron beam-physical vapor deposition(EB-PVD) of Ru and NiAlHf layer. The cyclic oxidation and interdiffusion of the Ru/NiAlHf coating at 1100°C was investigated by X-ray diffraction(XRD) and scanning electron micrograph (SEM) equipped with energy dispersive spectroscopy (EDS). The results show that the discontinuous Ru₂AlTa phase forms at the interface of coating and substrate at initial diffusion stage, which effectively inhibits outward diffusion of refractory elements in the superalloy. The phase disappears after 100 h annealing. The Ru/NiAlHf coatings effectively suppress the formation of secondary reaction zone (SRZ). No apparent scale spallation is observed on the Ru/NiAlHf coating even after 150 h cyclic oxidation, indicating that the coatings exhibit a good cyclic oxidation-resistance.