Abstract: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.

Key words: Ni₃Al−Mo based alloy; Re element; isothermal oxidation