Ni–Al composite coatings: diffusion analysis and coating lifetime estimation

Abstract The interdiffusion of Ni matrix/Al particle composite coatings and nickel substrates was studied using electron probe microanalysis (EPMA) and a one-dimensional diffusion model. The initial coating microstructure was a two-phase mixture of γ(Ni) and γ′(Ni 3 Al). The coating/substrate assemblies were aged at 800 to 1100°C for times up to 2000 h. It was found that aluminum losses to the substrate are significant at 1000°C and above. The experimental results for the diffusion of Al into the substrate were compared with model predictions based on a diffusion equation for a finite layer on an infinite substrate. Using combined experimental and model results, the effects of temperature and coating thickness were determined and a rationale was developed for coating lifetime prediction.