Anisotropy of interface characteristics between NiCoCrAlY coating and a hot corrosion resistant Ni-Based single crystal superalloy during thermal exposure at different temperatures

Abstract

Effects of crystal orientations and service temperatures on microstructural evolution of a coated hot corrosion resistant Ni-Based single-crystal superalloy containing carbon were investigated. γ′ grains nucleated at the interdiffusion zone (IDZ) and secondary reaction zone (SRZ) with formation of M23C6 and σ phases during thermal exposure at 900 °C. But for specimens exposed at 1000 °C, γ grains nucleated at the IDZ with precipitation of secondary MC carbides and many needle-like σ phases precipitated at the substrate-diffusion zone (SDZ). The interfacial microstructure stabilities exhibited opposite anisotropy during the thermal exposure at 900 °C and 1000 °C.