材料期刊网

The influence of sputtering on the high temperature oxidation resistance of the cast superalloy M17F has been studied. The as-sputtered microcrystalline layer has a homogeneous gamma phase structure with very fine gl ain size (20-100 nm), while the as-cast alloy is composed of gamma, gamma' and carbides. The oxidation resistance of the microcrystalline coating of K17F alloy is much better than that of the as-cast alloy, and is even superior to that of the pack aluminized alloy. At the initial oxidation stage, the oxide scale which formed on the as-cast alloy is composed of complex oxides of Cr, Ti, Ni and Al. As the: oxidation time is prolonged, the amount of alpha-Al2O3 increases and becomes the main product. However, the scale which formed on the microcrystalline coating consists only of alpha-Al2O3. Cyclic oxidation and acoustic emission examination showed that the oxide scale on the cast M17F alloy easily spalled during cooling, but the alpha-Al2O3 scale on the sputtered layer had excellent adhesion. The beneficial effects of microcrystalline structure on oxidation resistance are discussed briefly.