Effect of Al content on the lifetime of thermally grown oxide formed on Ni-Al alloys after isothermal oxidation

The effect of Al content on the spallation behaviour of the thermally-grown oxide (TGO) formed on Ni-Al alloys after oxidation at 1100 °C was investigated. It is found that the spallation of TGO increases with an initial increase of the Al content from 20% to 27.5%, and then decreases with further increase in the Al content up to 55%. It is proposed that the TGO spallation is driven by the effective stress near the TGO/substrate interface and restricted by the yielding strength of the substrate. Both the effective stress and yielding strength are influenced by the Al content.