X-ray Photoelectron Spectroscopy (XPS) analysis of low oxidation pressure behavior of FeAl-alloys at 600 degrees C and 700 degrees C

Abstract

The low oxidation pressure behavior of binary FeAl alloys has been examined at different temperatures of 600-700 degrees C. Polycrystalline and single-crystalline samples of Fe-10Al and Fe-25Al were oxidized for 1 h at 10-6 mbar of oxygen in an ultra-high-vacuum chamber (UHV). Prior oxidation, samples were prepared by sputter-annealing cycles in UHV. After oxidation, the samples were analyzed by X-ray Photoelectron Spectroscopy (XPS). The formed oxide layers on the surfaces consist of FeAl2O4 and Al2O3 showing that Al has a dominating role during the oxidation process. From XPS peaks, the composition of the Fe peaks of the oxide layer consists of Fe metal, FeAl-alloys, and FeO. Meanwhile, the composition of the Al peak is changed from Al metal, FeAl-alloys and Al2O3 at 600 degrees C to Al metal, FeAl-alloys and FeAl2O4 on 700 degrees C. From XPS sputter depth profiles, it is shown that the oxide layer was growing with increasing temperature, and the single-crystalline Fe-10Al has a thicker formed oxide layer than poly-crystalline Fe-25Al with same oxidation treatment.