Hot-stage nano-characterisations of an iron aluminide

Hot-stage nano-indentation tests have been performed to investigate the mechanical properties on the surface of Fe–40at.% Al, a B2-structured iron aluminide, at temperatures ranging from 25 to 400 °C. Nano-indentation and nano-scratch tests have also been performed after the samples were cooled down to room temperature to evaluate the effect of elevated-temperature exposure on the surface properties of the aluminide. The results show that the surface hardness of the investigated iron aluminide is higher and the elastic modulus is lower at elevated temperatures than at room temperature. XPS analysis reveals that mixed oxides of Al2O3 and Fe2O3 have been formed on the sample surface during the high-temperature nano-indentation tests. The in situ formed oxides have contributed to the increased surface hardness and reduced value of elastic modulus both at elevated temperature and after cooling down to room temperature. Nano-scratch tests show that the oxide layer formed at elevated temperature improves the abrasive wear resistance of the iron aluminide at room temperature.