Reaction diffusion analysis for interface between Ni based super alloy and MCrAlY coating
Itoh Yoshiyasu; Tamura Masataka; Takahashi Yasuo
Abstract:A computer aided interactive system for coating design has been developed, which enables to analyze conveniently the reaction diffusion of bonded materials. The object of this study is the overlay coatings of MCrAlY alloy sprayed by a low pressure plasma spray (LPPS) process for protection against high temperature corrosion and oxidation in the field of gas turbine components. However, the reaction diffusion behavior at the interface between the MCrAlY coating and the substrate, which has an important effect on coating degradation, has not always been clarified. Three kinds of substrate, such as equiaxis IN738LC, directional solidified CM247LC and single crystal CMSX 2, and four kinds of low-pressure plasma sprayed MCrAlY coating were selected for the experiments. The experimental results showed that the reaction diffusion layers consisted of aluminum compound layer and aluminum decrease layer, basically. However, the aluminum decrease layer could not be observed in the cases of CoNiCrAlY and NiCoCrAlY coatings. It was also indicated that each diffusion thickness changed in parabolic time dependence. And the order of reaction diffusion rate was NiCrAlY greater than CoCrAlY greater than CoNiCrAlY greater than NiCoCrAlY independent of the kind of substrate. It was also clear that the estimation of long time diffusion behavior by simulation analysis was possible in comparison with the experiments. Key Words:coating design, low-pressure-plasma spray, MCrAlY coating, Ni based super alloy, reaction diffusion, parabolic time law, diffusion rate constant