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

The interdiffusion of Ni matrix/Al particle composite coatings and nickel s ubstrates was studied using electron probe microanalysis (EPMA) and a one-d imensional diffusion model. The initial coating microstructure was a two-ph ase mixture of gamma (Ni) and gamma (Ni3Al). The coating/substrate assembli es were aged at 800 to 1100 degreesC for times up to 2000 h. It was found t hat aluminum losses to the substrate are significant at 1000 degreesC and a bove. The experimental results fur the diffusion of Al into the substrate w ere compared with model predictions based on a diffusion equation for a fin ite layer on an infinite substrate. Using combined experimental and model r esults, the effects of temperature and coating thickness were determined an d a rationale was developed for coating lifetime prediction. Published by E lsevier Science Ltd on behalf of Acta Materialia Inc.