Formation of high-temperature inner oxide scale on low alloy steels: Segregation, partitioning and transformation reactions

Abstract

High-temperature oxide scales on two low-alloy steels were carefully studied. For the first time, the FeO inner scale on the steel with low Cr and Si contents is observed to incur a eutectoid reaction in a divorced mode during cooling, resulting into a bimodal Ni distribution near the scale/substrate interface. In contrast, a combination reaction of oxygen and FeO layer occurs on the steel with high Cr and Si contents where cracks in scales provide pathway for oxygen transport, and a fine-grained nanocomposite oxide band develops near the interface. Dealloying, partition and segregation during the scale formation are comprehensively addressed.