Influence of atmosphere on high-temperature oxidation of Fe-Cr-Si model alloy

The aim of this study is to show the influence of the gaseous environment on the ferritic Fe-Cr-Si model alloy oxidation during 70 hrs, at 900 and 950 degrees C. Two different atmospheres have been used, air or nitrogen containing 5 vol% hydrogen (N-2-5%H-2). After air oxidation, a nonadherent chromia scale formed. In the N-2-5%H-2 gaseous environment, it clearly appears that silicon segregation near the internal scale-metal interface is favoured. In this low oxygen-containing gas, adherent chromia, and silica scales have been formed. Silica subscale associated to an adherent chromia scale obtained in low-oxygen conditions are a good protection barrier against carburisation.