Internal oxidation of austenitic Fe-Ni-Cr alloys at high temperatures: Deduction of oxygen permeability and the influence of carbon-bearing gases

Internal oxidation was employed to determine oxygen permeability in the Fe-Ni system between 1000 ºC and 1150 ºC at the oxygen partial pressures of Fe/FeO equilibrium. Fe-Ni-Cr alloys were exposed to environments with and without carbon to assess the influence of dissolved carbon on oxygen permeability. A detailed examination of the classical diffusion model for internal oxidation allowed increased accuracy of the permeability measurement. Oxygen permeability decreased nonlinearly with Ni content in the alloy, driven by a decrease in oxygen solubility. No carbon effect was detected in Ni-containing alloys.