Low-temperature oxy-nitriding of 316 L austenitic stainless steel for improved corrosion resistance in liquid lead-bismuth eutectic

The effects of low-temperature oxy-nitriding (LTON) treatment on the liquid lead-bismuth eutectic (LBE) corrosion behaviors of 316 L ASS were investigated in the stagnant liquid LBE under vacuum at 823 K. Results show that the untreated samples were severely selective leaching in contact with liquid LBE. LTON treatment produced an outer porous Fe-Cr spinel film and inner S phase layer on the sample surface, which transformed into a thicker spinel film containing γlow-N and a region distributed with CrN precipitates after liquid LBE corrosion. This was mainly attributed to the oxidation and decomposition of S phase and inward diffusion of the interstitials, owing to S phase is a metastable phase and is easier to be oxidized than matrix at elevated temperatures. This inspired us that improving the ability to form protective oxide film for materials was maybe a good method to mitigate the liquid LBE corrosion.