Oxygen Diffusion Study in Oxidation Films of the AISI 304 Austenitic Stainless Steel

Abstract

Oxygen ion diffusion coefficient was measured, for the first time, in oxide films grown by the high temperature oxidation of the AISI 304 austenitic stainless steel. The steel samples were polished and then oxidized in synthetic air in order to grow the chromia oxide (Cr2O3) film. The oxygen diffusion experiments in the oxide films were performed by using the18O isotope as oxygen tracer. The isotope diffusion studies were performed from 750 to 900o C, in Ar +21%18O2 atmosphere and the oxygen ion diffusion profiles were established by secondary ion mass spectrometry (SIMS) analysis. From the18O diffusion profiles, the bulk, effective and grain boundary diffusivities were determined. Using Wagner´s theory, it is shown that, under the used experimental conditions, the oxygen ion diffusion is large enough to assure the growth rate of the chrome oxide films formed by the oxidation of the AISI 304 stainless steel.