Microstructure of Pt-modified aluminide coatings on Ni-based superalloys

This study deals with the microstructure of a Pt-modified aluminide coating as a function of the treatment parameters. IN 100 (polycrystalline) and AM 1 (single crystal) superalloys have been used as substrates and coated by an Aluminizing Phase Vapor Snecma® low-activity treatment developed by Snecma-Services. By using the Fisher experiment design method, we have shown that the aluminum quantity incorporated in the coating depends essentially on the donor, and that the presence of important amounts of platinum at the surface allows a better incorporation of this aluminum through the reaction Pt+2Al→PtAl2. This latter phase then transforms into (Ni, Pt)Al during the aluminizing treatment. The results of this investigation allow to describe the microscopic aluminizing mechanisms.