Stability of MnCr2O4 spinel and Cr2O3 in high temperature carbonaceous environments with varied oxygen partial pressures

In this investigation, Cr2O3 and MnCr2O4 were comparatively tested at 1050 °C in carbonaceous environment with varied oxygen partial pressures. MnCr2O4 exhibits much better resistance to carbonaceous attack than Cr2O3. The carburization rate of MnCr2O4 decreases sharply with increasing oxygen partial pressures. The oxygen partial pressures have less effect on the carburization resistance of Cr2O3. The increased resistance of MnCr2O4 to carburization is attributed to the dissolution of MnO into Mn–Cr–O spinel lattices with elevated oxygen partial pressures, which retards the decomposition and carburization of Mn–Cr–O spinel. The thermodynamic equations defining the carburization stability of MnCr2O4 and Cr2O3 are modified.