Effects of pre-formed nanostructured surface layer on oxidation behaviour of 9Cr2WVTa steel in air and liquid Pb–Bi eutectic alloy

•Surface mechanical rolling treatment was applied to 9Cr2WVTa steel.•Microstructure in the surface layer of the steel was refined into nanometer scale.•Oxidation resistance of the nanostructured sample is evidently enhanced in air.•Oxide scale on the nanostructured sample is more compact and enriched with Mn.•Oxide scale on the nanostructured sample is more protective in liquid Pb–Bi.

A nanostructured surface layer was pre-formed on a 9Cr2WVTa reduced activation ferritic/martensitic steel sample by means of surface mechanical rolling treatment (SMRT). In comparison with the initial sample, oxidation experiments at 600 °C in air showed that the oxidation resistance of the SMRT sample is markedly enhanced, due to the formation of a more continuous, homogenous, and compact oxide scale enriched with Mn. Furthermore, oxidation experiments at 550 °C in oxygen-saturated liquid Pb–Bi eutectic alloy showed that the oxidation resistance is improved on the SMRT sample after pre-oxidation in air, due to depressed diffusivities in the pre-formed oxide scale.