Spontaneous reaction formation of Cr23C6 diffusion barrier layer between nanocrystalline MCrAlY coating and Ni-base superalloy at high temperature

A nanocrystalline NiCrAlYHfSi coating was prepared by magnetron sputtering. The coating after post-annealing comprised matrix γ′-Ni3Al and α-Cr precipitates. No coating spallation was observed after 100 cycles of 1000-25 °C water-quenching test. A continuous Cr23C6 interlayer between the coating and the substrate was spontaneously formed during high temperature exposure, and exhibited good performance in suppressing the coating/substrate interdiffusion. The α-Cr precipitates in the coating disappeared gradually as Cr in the coating was consumed to form the Cr23C6 interlayer. Its growth rates can be fitted into a law controlled by two completing processes: a parabolic growth and a linear decomposition.