The effect of Zr on high-temperature oxidation behaviour of Fe3Al-based alloys

The cyclic oxidation of Fe-30Al-xZr and Fe-25Al-xZr (x = 0.3-5.2 at.%) has been investigated at 900 °C and 1100 °C in laboratory air. Scales, oxide protrusions and structural changes were analysed by LOM, XRD, SEM and EDS. The oxidation rate increases with increasing Zr content as well as with increasing temperature. Spallation of thin scales formed at 900 °C on the Zr lean alloys is observed, while thicker scales formed on Zr-rich alloys or at 1100 °C show cracking but do not spall. At both temperatures the scales on all alloys consist of Al2O3, Fe2O3 and ZrO2 and oxide protrusions penetrate into the samples. These protrusions form by preferential oxidation of Zr rich phases.