Effect of grain size on the oxidation of Fe–13Cr–5Ni alloy at 973 K in Ar–21 vol%O2

•Oxidation kinetics was fitted by mixed model with linear and parabolic behaviour.•Decreasing the grain size promoted intergranular oxidation of transition alloy.•Grain refinement contributed to faster transition to the steady state oxidation.•Effect of grain refinement to oxidation is mainly on inward oxidation process.

Effect of grain refinement from 370 to 34 μm on oxidation of transition Fe–13Cr–5Ni alloy at 973 K in Ar–21 vol%O2 was investigated. The measured weight gains were fitted taking into account a mixed kinetic model with an initial linear and subsequent parabolic growth behaviour. Different scale microstructural evolution was discussed. Contribution of grain refinement to the oxidation is predominantly due to its effect on the inward oxidation process. Decreasing grain size promoted intergranular oxidation, accelerated formation of the Cr-containing inner scale, contributed to the faster transition to the steady state oxidation and correspondingly slightly improved the oxidation resistance.