Effects of silicon additions on the oxide scale formation of an alumina-forming austenitic alloy

This study investigated the effect of silicon additions on the oxidation behaviour of an alumina-forming austenitic (AFA) stainless steel at high temperatures in air with 10% water vapour. The AFA steels exhibited good oxidation resistance with less than 0.3 wt.% Si due to the formation of a dense, continuous and protective Al2O3 scale. However, silicon additions of more than 0.3 wt.% stimulated B2-NiAl precipitation and reduced the Al concentration in the austenite matrix, leading to its degradation with oxidation resistance at 800 °C in air with 10% water vapour.

► Additions of Si can transform the oxidising mode in the AFA steel.
► Excessive Si additions degraded the oxidation resistance of the AFA steels.
► Si stimulates precipitation of the NiAl and reduces the Al content in the matrix.