Original paper(Vol.45 No.11 pp.1211)

Basic study of high-temperature protective coating design based on reaction diffusion analysis

Itoh Yoshiyasu; Tamura Masataka; Takahashi Yasuo

Abstract:A computer-aided interactive system for coating design has been developed, which enables to conveniently analyze the reaction diffusion of bonded materials. The object of this study is to examine the overlay coating 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 gives 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 the low-pressure-plasma sprayed CoCrAlY coating are selected for the experiments.
The experimental results showed that the reaction diffusion layers consisted of aluminum compound layer and CoAl decrease layer. It also indicated that the diffusion thickness changed according to the parabolic time dependence. The reaction diffusion rates of the CM247LC and CMSX-2 were faster than the IN738LC. It was also clear from the simulation analysis that the diffusion distance during heating process should not be ignored in the total diffusion distance.

Key Words:coating design, low-pressure-plasma spray, CoCrAlY coating, equiaxials IN738LC, directional solidified CM247LC, single-crystal CMSX-2, reaction diffusion, parabolic time law, diffusion rate constant