The microstructure evolution during the vacuum heat treatment for a Re doped Ni2Al3 coating on a Ni-based single crystal superalloy

Abstract To figure out the microstructure evolution of a Re doped Ni2Al3 coating during vacuum heat treatment, the sample was heated to 1050 ℃ for 2 h and then transformed to Re doped β-NiAl coating. Re-doped β-NiAl coating was consisted of four layers including a layer with holes, β-NiAl and fine dispersed Re, a layer with β-NiAl and fine dispersed Re, a layer with β-NiAl and fine dispersed W-rich precipitates and a bottom layer of interdiffusion zone (IDZ). The β-NiAl type coating was primarily formed by outward diffusion of Ni from the substrate to react with Al of Re doped Ni2Al3 coating. Moreover, the inward diffusion of Al also occurred, thus the formation of holes was attributed to the counter diffusion of vacancies in outer coating.