MCrAlY溶射皮膜のアルミニウム拡散浸透処理特性
1996 年 45 巻 2 号 p. 218-223
詳細
1996 年 45 巻 2 号 p. 218-223
A low-pressure-plasma spray (LPPS) process is used for the overlay coating of MCrAlY alloy to protect it against high temperature corrosion and oxidation. This coating process has been found to be very effective for gas turbine components. On the other hand, a diffusion coating process has been applied for many years to improve similarly the environmental resistance by enriching the surface of a substrate in Cr, Al, or Si. Recently, aluminizing on MCrAlY coating is used for improving further the high temperature oxidation resistance. However, the aluminizing properties of plasma-sprayed MCrAlY coating, which have an important effect on the coating performance, have not been clarified. In this study, five kinds of plasma-sprayed MCrAlY (CoCrAlY, CoNiCrAlY, CoNiCrAlY+Ta, NiCrAlY, NiCoCrAlY) coating were selected for the aluminizing tests. The heat treated MCrAlY specimens (1393K, 2h, Ar atmosphere) were pack-aluminized at 1173, 1223 and 1273K for 5, 10 and 20h, respectively.
The experimental results showed that the aluminum rich layer of NiAl or CoAl phase was formed by aluminizing. It was also indicated that the thickness of the aluminum rich layer showed parabolic time dependence. There is a tendency that the reaction diffusion rate by aluminizing increases with increasing nickel content in the MCrAlY coating.
