Effect of Re element on oxidation resistance of Ni ₃Al-Mo based alloys at 1150°C

The isothermal oxidation behaviors of three kinds of Ni ₃Al-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, NiAl ₂O ₄ and a small amount of NiMoO ₄, and an inner layer of NiAl ₂O ₄ and Al ₂O ₃. 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.