A new method to develop a NiRe-Al2O3 diffusion barrier between single crystal Ni-base superalloy and NiAl coating

Abstract

Formation of a thick interior interdiffusion zone (IDZ) dispersing brittle topologically close packed (TCP) precipitates is a key factor of unacceptably damaging the high temperature creep resistance of advanced single crystal (SX) Ni-base superalloy, when it is coated with conventional NiAl coating and exposed to high temperature environment. In this work, a NiRe-Al2O3 layer between the NiAl coating and the SX Ni-base superalloy was developed by electrophoretic deposition of α-Al2O3 nanoparticles followed by NiRe alloy electrodepostion. The 100 h oxidation at 1050 °C indicates that the intermediate layer worked well as a diffusion barrier (DB), not only decreasing the thickening rate of deterioration zone in the superalloy, but also totally preventing the coating from being penetrated by refractory elements from the underlying alloy and DB, which is always observed for typical metallic DBs. The beneficial effect of the new DB on interdiffusion is discussed.