Enhanced oxidation resistance of a reduced activation ferritic/martensitic steel in liquid Pb-Bi eutectic alloy by preforming a gradient nanostructured surface layer

A gradient nanostructured (GNS) surface layer with a thickness of ∼250 μm was produced on an 11Cr-WVTaSi reduced activation ferritic/martensitic (RAFM) steel by means of surface mechanical rolling treatment (SMRT). The mean grain size was ∼53 nm at the topmost surface layer and increased gradually with increasing depth. The oxidation behavior of the GNS sample was compared with that of the coarse-grained counterpart in an oxygen-saturated liquid lead-bismuth eutectic (LBE) alloy at 550 °C. The results showed that the oxidation resistance of the GNS sample was significantly enhanced in the liquid LBE alloy after different immersion times up to 3500 h. This was mostly due to the accelerated formation of a dense and protective spinel scale enriched with Si and Mn on the GNS sample.