High-temperature oxidation of oxide-dispersion-strengthened FeCrAl alloys: Influences of Al, Co and Y concentration on the mechanism of oxide scale growth

Oxide-dispersion-strengthened (ODS) FeCrAl alloys with different Al and Co contents were oxidized at 800 degrees C in air, and the oxidation behavior was investigated. The oxidation mass gain was measured, and the phase and morphology of the oxide scale were characterized using XRD, SEM, and STEM. The elemental distribution of the oxide layer was determined by EPMA. The results demonstrated that protective alpha-Al2O3 scales were generated on the surface of alloys containing 3 and 5 wt% Al. After 225 h of oxidation, the mass gain of alloys with 5 wt% Al decreased as Co concentration increased, whereas the 3 wt% Al alloys exhibited the reverse tendency. The ferritic matrix and lower oxidation temperature promoted the external Al2O3 scale formation on the 3Al alloys. It is proposed that the balance between matter diffusion blocking through the oxide grain boundary and grain coarsening determines how the Y/Y2O3 concentration affects the oxidation kinetics. The minor addition of Y/ Y2O3 decreases the oxidation kinetics of FeCrAl-ODS alloys, whereas excess addition is detrimental to the oxidation behavior of the alloy. A plausible model for analyzing the influence of Co and Y concentration on the oxidation kinetics of FeCrAl alloys containing 3 and 5 wt% Al was proposed. The findings could serve the fundamental alloying design to realize the transformable FeCrAl-ODS alloys for high-temperature applications.