Transient Oxidation Behavior of Fe-5wt.%Al Alloy at 1073 K in Atmospheres Containing Both Oxygen and Water Vapor

摘要

The transient oxidation behavior of Fe-5wt.%Al alloy was investigated at 1073 K. Alloys were oxidized in two atmospheres, where gas compositions were changed from an initial N2-12.2H2O or O2-12.2H2O to N2-0.9O2-12.2H2O and vice versa. When the gas composition was changed from N2-12.2H2O to N2-0.9O2-12.2H2O and also from N2-0.9O2-12.2H2O to N2-12.2H2O or O2-12.2H2O, the oxidation kinetics and scale structures rapidly changed. When the gas composition was changed from O2-12.2H2O to N2-0.9O2-12.2H2O, the oxidation kinetics changed after a 1.5-hsec delay. When the alloy was oxidized rapidly, dissociative fissures were generated and grew. The formation and extinction of these dissociative fissures was strongly influenced by the oxygen contents. It is suggested that the oxidation kinetic were affected by dissociation reactions and that this was controlled by the oxygen-activity gradient across the scale.