Abstract
Recently, the aluminizing of MCrAlY 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 MCrAlY coatings, which have an important effect on coating performance, have not alway been clarified. In this study, five kinds of as-sprayed MCrAlY (CoCrAlY, CoNiCrAlY, CoNiCrAlY+Ta, NiCrAlY, NiCoCrAlY) 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 NiAl or CoAl 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 MCrAlY coatings and the reaction diffusion rate of as-sprayd MCrAlYs is faster than that of the heat treated MCrAlYs (1393K, 2h, Ar atmosphere) in all cases.
