Surface Oxidation of Type 316 Stainless Steel

Abstract

Surface analyses of type 316 stainless steel (SUS 316) oxidized in air were carried out by means of SIMS, ESCA and SEM . Composition vs depth profiles of SUS 316 as received showed Cr depletion at the topmost surface layer and Cr enrichment in the under layer. This may be explained by the selective oxidation of Fe at the topmost surface which results in diffusion of Fe towards the surface. With oxidation in air at 600–800°C, samples as received showed the growth of Fe-rich surface oxide, while, mechanically polished specimens generated Cr-rich oxide, which possessed protective nature against oxidation at lower temperatures. However, once the Fe-rich oxide is nucleated on the polished specimen at higher temperatures, it grew faster than Cr-rich oxide and spread over the initially formed Cr-rich oxide. Nickel plays a minor role in oxidation and its content in the oxide layer was very depressed.