High-temperature oxidation behavior of DZ125 Ni-based superalloy under tensile stress

The key in antioxidant capacity of aero-engine hot components is the protective oxide scales. Many factors can affect the performance of oxide scales. The effect of tensile stress on high-temperature oxidation behavior of directionally solidified DZ125 Ni-based superalloy was investigated by thermogravimetric analysis (TGA). Tensile samples were subjected to stress of 100 MPa, and the oxidation behavior was studied at 980 °C in air. The surface and cross-sectional morphologies of the oxidized coating were analyzed by scanning electron microscope (SEM). The influence of tensile stress on the oxidation behavior of directionally solidified DZ125 Ni-based superalloy at high temperature was discussed. Results show that an applied tensile stress generally leads to larger Cr/Ni mass ratio in the oxide scales, greater overall chromium depletion values directly under the oxide scales, lower specific weight gain values and thinner oxide scales. These factors are attributed to the formation of fast diffusion paths for Cr atoms to diffuse to the surface under tensile stress, thus causing a reduction in the duration of the less protective transient oxidation period and promoting a faster formation of the protective Cr₂O₃ layer.