Oxidation mechanism and kinetics of nuclear-grade FeCrAl alloys in the temperature range of 500–1500 °C in steam

The oxidation mechanism and kinetics of two nuclear-grade FeCrAl alloys were investigated in steam up to 1500 °C by transient and isothermal oxidation tests. The slow α-alumina formation kinetics well matched only for the temperature range from 1000 °C to 1300 °C. Below 1000 °C, formation of transient alumina caused faster kinetics. In addition, an excessive Fe-rich oxide formation was observed on the inner surface due to rough surface at 600 °C. Above 1300 °C, convoluted α-alumina was easily spalled and caused faster kinetics. Moreover, the oxide spallation caused Cr and Al depletion and catastrophic oxidation above 1400 °C by the formation of Fe-rich oxide. The catastrophic oxidation caused a liquid phase in Fe-rich oxides, which significantly changed the tube segment geometry.