Ni-Al composite coatings: Diffusion analysis and coating lifetime estimation

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 (Ni3Al). The coating/substrate assemblies were aged at 800 to 1100 degreesC for times up to 2000 h. It was found that aluminum losses to the substrate are significant at 1000 degreesC and above. The experimental results fur 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. Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.