Revealing the oxidation mechanism of high vanadium high-speed steel using multi-scale characterization

The microstructure evolution of the oxide scales formed in high vanadium high-speed steel after exposure to 500 degrees C and 700 degrees C for up to 120 min was investigated using multi-scale characterization. The oxide scale showed a triplex structure consisting of internal oxide layer, inner oxide layer, and outer oxide layer. The internal and outer oxides formed were Cr2O3 and Fe3O4, respectively. The progressive increase in oxygen partial pressure resulted in the conversion of Cr2O3 to FeCr2O4 in the inner oxide layer with nanocavities. The "available space model" and the "internal oxidation model" were identified as controlling oxidation mechanisms.