Inhibiting effect of Ni-Re interlayer between Ni-Al coating and steel substrate on interdiffusion and carburization

A Ni-Re film was electroplated as a diffusion barrier between the Ni-Al coating and the iron alloy substrate. The interdiffusion between the coating and the substrate was investigated by micro-structure analysis, and the interdiffusion coefficient was calculated using Boltzmann-Matano method. The results indicated that the Ni-Re interlayer played a superior barrier effect, almost fully blocking interdiffusion and retarding the formation of diffusion zone (DZ). The Ni-Al coating without a diffusion barrier showed severe carburization corrosion in the diffusion zone during carburization process, while the Ni-Al coating with the Ni-Re diffusion barrier effectively protected the steel substrate from carbon attack.