ニッケル基超合金へのアルミニウム-珪素複合拡散被覆

Abstract

The aluminum-silicon multi-component diffusion coating, using the powder pack process, was applied to nickel and Inconel X-750 to investigate the oxidation resistance and the high-temperature corrosion resistance of the specimens.The results obtained are as follows:(1) Effects of the blending ratio of silicon in the pack material on the high-temperature oxidation resistance were examined. It was found that when 24 mass% aluminum, 6 mass% silicon, 67 mass% alumina and 3 mass% ammonium chloride were used, a coating with excellent high-temperature oxidation resistance was obtained.(2) The aluminum-silicon multi-component diffusion coating using pack material containing more than 6 mass% silicon, and another coating by reduction of silicon dioxide with aluminum, were tried, but neither was effective in improving the high-temperature oxidation resistance.(3) In an Al-Si treated layer containing 6 mass% silicon, the presence of a small amount of Si was observed at the interface between the treated layer and the basis metal before oxidation. It was also confirmed that the oxide layer consisted of silicon oxide on the surface and aluminum oxide beneath.(4) The specimen treated by the aluminum-silicon multi-component diffusion coating showed excellent resistance to high-temperature corrosion, which may be caused by synthetic ashes, V2O5-Na2SO4 and Na2SO4-NaCl. Particularly the specimen treated by the aluminum-silicon multi-component diffusion coating using silicon dioxide has better corrosion resistance than that treated by aluminum-silicon multi-component diffusion coating using silicon.