Effect of Surface Roughness on the Oxidation Behavior of a Directionally Solidified Ni-Based Superalloy at 1,100 °C

The effect of surface roughness on the oxidation behavior of a directionally solidified Ni-based superalloy was investigated by surface mapping microscope, scanning electron microscope and X-ray diffraction. It was found that specimens with surface roughness of 0.05 µm exhibit the best oxidation resistance, while specimens with surface roughness of 0.14 µm behave worse than specimens with surface roughness of 0.83 µm. The specimens with surface roughness of 0.05 µm have the best oxidation resistance, which is mainly due to the smallest surface area exposed in air and thinnest work-hardening layer. The Al2O3 layer alleviates the oxidation process of the specimens with surface roughness of 0.83 µm, and this is the possible reason for the better oxidation resistance of samples with surface roughness of 0.83 µm than samples with surface roughness of 0.14 µm.