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 #gamma# (Ni) and #gamma#′ (Ni_3Al). The coating/substrate assemblies were aged at 800 to 1100 deg C for times up to 2000 h. It was found that aluminum losses to the substrate are significant at 1000 deg 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.
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