Oxidation behavior of novel rail steels at 500°C

Thermo gravimetric analysis (TGA) was used to study isothermal oxidation behavior of four novel rail steels at 500∧C in static air condition. These steels contained different combinations of microalloying elements, Cu, Cr, Ni and Si. The results were compared with the oxidation behavior of three rail steels already in commercial application (C-Mn, Cr-Mn and Cu-Mo). The lowest parabolic rate constant was obtained in case of Cr-Cu-Ni-Si contained rail steel. Spallation of the oxide layer was not observed in any of the rail steels. C-Mn, Cu-Mo and Cu-Si rail steels showed higher values of parabolic rate constants kp. In contrast to others Cu-Si exhibited linear rate law and larger weight gain compared to all other rail steels. X-ray diffraction (XRD) analysis confirmed that the major phase in the oxides was magnetite (Fe3O4). The surface morphology of the oxide scales were correlated with the oxidation rate.