Abstract:The oxidation kinetics of GH3230 alloy was measured as a function of the cumulative time cyclically exposed upto 1200℃. The oxidation behaviors and the resulting composition and microstructure of the near surface layer were observed and analyzed by SEM, XRD and EPMA. It has been found that GH3230 alloy exhibits continuous oxidation weight loss during cyclic thermal exposures, and the weight loss rate decreases from the highest value to lowest level and then gradually increases with the thermal exposure time. Nevertheless, the alloy-thickness loss after 100 exposure cycles can be obviously less than the thickness-fluctuation limit of standardized plate products. The remaining oxides on the surface after heat exposure are mainly composed of Cr2O3 and MnCr2O4. The normal gas pressure produced by carbon oxidation, the increments of oxide growth stress and the thermal stress caused by over-temperature exposure lead to the cracking and spallation of the outer oxides. At mean time, internal oxidation occurs along grain boundaries significantly. While, it is worthy to note that the depth of the Ni-based solid solution layer tranformed through selective oxidation and oxidative decarbonization is always much larger than that of the internal oxidation. It indicates that the cracks initiated from the intergrannual oxides as the materials bearing tensile load will soon be blunted by in-front ductile FCC-stucture solid solution and therefore present negligible impact on the mechanical performance of GH3230 alloy.