Temperature dependence of metastable alumina formation during thermal oxidation of FeCrAl foils

Industrial FeCrAl foils were isothermally oxidized during 5 hours between 850 and 1000°C in atmosphere of pure oxygen. Characterization of transition and α-alumina phases was performed by XRD and XPS, using reference spectra obtained by various air annealing treatments of pure γ-Al2O3. An original model was proposed to deconvolute XPS spectra to obtain quantification of transition alumina formation and transformation. At 850°C, oxide scales on FeCrAl consisted of transition alumina, whereas higher temperature treatments resulted in decreased amounts of transition aluminas and in increasing α-alumina formation. At 1000°C, the highest temperature studied, the scale could be described by XPS and XRD as pure alpha.