Original paper(Vol.45 No.2 pp.224)

Aluminizing properties of low-pressure-plasma sprayed coatings

Itoh Yoshiyasu; Saitoh Masahiro; Harada Yoshio; Takeuchi Jun-ichi

Abstract:Recently, the aluminizing of MCrA l-script Y coatings sprayed by a low-pressure-plasma spray (LPPS) process is used for improving the high temperature oxidation resistance. However, the aluminizing properties of plasma-sprayed MCrA l-script Y coatings, which have an important effect on coating performance, have not always been clarified. In this study, five kinds of as -sprayed MCrA l-script Y (CoCrA l-script Y, CoNiCrA l-script Y, CoNiCrA l-script Y+Ta, NiCrA l-script Y, NiCoCrA l-script Y) coatings were selected for the aluminizing test. The pack -aluminizing was conducted at 1173, 1223 and 1273K for 5, 10 and 20h, respectively.
The experimental results showed that the aluminum rich layers of NiA l-script or CoA l-script phase were formed by the aluminizing process. It also indicated that the thickness of the aluminum rich layers could be determined, by the parabolic time dependence. There is a tendency that the reaction diffusion rate by the aluminizing increases with increasing nickel content in MCrA l-script Y coatings and the reaction diffusion rate of as -sprayed MCrA l-script Ys is faster than that of the heat treated MCrA l-script Ys (1393K, 2h, Ar atmosphere) in all cases.

Key Words:low-pressure-plasma spray, as-sprayed McrAlY coating, aluminizing, reaction diffusion, parabolic time law, diffusion rate constant, nickel aluminide, cobalt aluminide