Scaling behavior of two Fe-xCr-5Si alloys under high and low oxygen pressures at 700 °C

The oxidation of the Fe-5Cr-5Si and Fe-10Cr-5Si alloys has been examined under 1 and 10−20 atm O2 at 700 °C. In all cases the Cr additions improved the oxidation resistance of the Fe-5Si alloy by forming protective external scales rich in Cr- and Si-oxides, except for the oxidation of Fe-5Cr-5Si under the low oxygen pressure. Their scaling behavior has been interpreted using the kinetic diagrams of the Fe-Cr-Si system, predicted by calculating the critical concentrations of silicon and chromium needed to avoid their single or coupled internal oxidation on the basis of an extension of a criterion originally proposed by Wagner.