Effect of 0.1 wt% N on the pitting and stress corrosion cracking behaviour of as welded and post weld heat treated austenitic stainless steel weld

The present study deals with the effect of heat treatment on the pitting and stress corrosion cracking behavior of type 316L stainless steel weldment containing no nitrogen and 0.1wt% nitrogen. Tungsten Inert Gas (TIG) welding of 316L stainless steel was carried out with 317L filler wire. Nitrogen was introduced in the Argon shielding gas to an extent as to obtain 0.1wt% N in the resultant weld. Welds were also prepared without nitrogen in the shielding gas. Welds were subjected to pitting scan in 3.5 wt% NaCl solution and Stress Corrosion Cracking (SCC) studies conducted in acidic chloride solution of 5N H2SO4 and 0.5N NaCl. To investigate the effect of nitrogen, when welds are exposed to high service temperatures, the above tests were also conducted on the welds heat treated at 973K for 5 h. Presence of nitrogen considerably reduced the retained delta-ferrite in the welds. Nitrogen addition and aging did not alter the pitting tendency of the welds. However, the beneficial effect of nitrogen was more apparent in promoting SCC resistance of thermally aged welds