Susceptibility of As-Welded and Thermally Aged Type 316LN Weldments Toward Pitting and Intergranular Corrosion

Abstract

Abstract In this study, an attempt was made to investigate the pitting and intergranular corrosion susceptibility of as-deposited and thermally aged weldments of type 316LN stainless steel (SS) made by shielded metallic arc (SMA) welding process using 316 SS filler wires having a carbon content of 0.059 wt%. The delta-ferrite content, which was 4.5 FN (Ferrite Number) for the as-welded samples, changed to 0.3 FN after the aging treatment (1023 K/5 h). Initial delta-ferrite on thermal aging decomposed to various secondary phases like sigma and M23 C6 and chi. These phases were confirmed metallographically and identified by the powder x-ray diffraction method. Pitting corrosion resistance was determined at ambient temperature in neutral chloride and acidic chloride media on both as-welded and thermally aged weld metal samples by anodic polarization technique. The results indicated that in neutral and acidic chloride media, the pitting corrosion resistance of thermally aged samples was lower compared to that...