Effect of Re element on oxidation resistance of Ni3Al-Mo based alloys at 1150 °C

The isothermal oxidation behaviors of three kinds of Ni3Al-Mo based alloys at 1150 °C were studied. The morphology, structure and element distribution of oxide scales of the alloys were researched by scanning electron microscopy, X-ray diffraction and electron probe microanalysis. The research results show that there are three oxide layers, an outer layer of NiO, an intermediate layer mainly composed of NiO, NiAl2O4 and a small amount of NiMoO4, and an inner layer of NiAl2O4 and Al2O3. Re element was mainly distributed in the intermediate layer, which plays a role as “diffusion barrier” in the process of oxidation, and effectively reduces the diffusion rate of Al and Mo elements outward and diffusion rate of O element inward. As a result, a Al-rich oxide layer formed in the inner layer inhibits the growth of oxide layer and improves the oxidation resistance of the alloy.