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 degrees C by transient and isothermal oxidation tests. The slow alpha-alumina formation kinetics well matched only for the temperature range from 1000 degrees C to 1300 degrees C. Below 1000 degrees 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 degrees C. Above 1300 degrees C, convoluted alpha-alumina was easily spalled and caused faster kinetics. Moreover, the oxide spallation caused Cr and Al depletion and catastrophic oxidation above 1400 degrees 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. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

The oxidation mechanism and kinetics of two nuclear-grade FeCrAl alloys were studied in high-temperature steam. The formation kinetics of slow alpha-alumina matched well in the temperature range of 1000°C to 1300°C. Below 1000°C, transient alumina formation resulted in faster kinetics. Excessive Fe-rich oxide formation was observed on the inner surface at 600°C due to surface roughness. Convoluted alpha-alumina was easily spalled at temperatures above 1300°C, causing faster oxidation kinetics. The spallation of oxide led to Cr and Al depletion and catastrophic oxidation above 1400°C, forming Fe-rich oxide with a liquid phase that significantly changed the tube segment geometry.