Localised corrosion susceptibility of nitrogen-containing type 316LN stainless steel in cold work and thermally aged conditions

Abstract

In the present paper, an investigation was carried out to understand the microstructure or secondary phase changes formed during thermal ageing at nose temperature (where Cr diffusion was faster) and its influence on the pitting corrosion behaviour of type 316LN SS with marginally lower Cr in as-received (AR) and 10% cold work (CW). X-ray diffraction studies confirmed Cr₂₃C₆ and Cr₂N in AR and CW conditions. On thermal ageing, AR material from 0 to 10 h and CW from 10 to 24 h, although with lower Cr, the degree of sensitisation (DOS) and pitting potential (E _pit) were insignificant due to nitrogen where as above 10 h in AR condition and below 10 h in CW condition resulted reductions in pitting potential (E _pit) in different chloride mediums. These results provide new insights on the interplay between pitting, microstructures, alloying elements.