Microstructure of Pt modified aluminide coatings on Ni-based superalloys without prior Pt diffusion

This study deals with the microstructure of a Pt modified aluminide coating obtained with an aluminizing treatment without prior Pt diffusion. IN100 (polycrystalline) and AMI (single crystal) superalloys have been used as substrates and coated by an Aluminizing Phase Vapor Snecma (APVS (R)) low activity treatment developed by Snecma-Services. By using the Fisher experiment design method, we have shown that three types of microstructures can be obtained, depending on the type of the donor: a monophased (Ni, Pt)AI, a first two-phased PtAl2/NiAl, or a second two-phased PtAl2/NiAl with a continuous PtAl2 layer. Moreover, the presence of platinum at the surface allows a better incorporation of aluminum by comparing the aluminizing treatment with prior Pt diffusion. Finally, stability of the newly observed two-phase structure PtAl2/NiAl with a continuous PtAl2 layer at the surface has been investigated. (c) 2004 Elsevier B.V. All rights reserved.