Effect of Post Weld Stress Relieving on Intergranular Corrosion Resistance of Austenitic Stainless Steels

This paper deals with the applicability of various techniques for the assessment and quantification of sensitisation in Austenitic Stainless Steel Tungsten Inert Gas (TIG) welds. Welded joints of AISI Type 321 stainless steel were stress relieved at 760°C for period of up to 10 h. The base and weld metal components of the stress relieved joints were then assessed for susceptibility to sensitisation and Intergranular Corrosion (IGC) by using various tests specified by ASTM A262, Practices A and E (Strauss Test). The possibility of using Eddy Current Testing (ECT) to detect Degree of Sensitisation (DOS) and IGC was also assessed. The use of ASTM A262 Practice A and E tests indicated sensitisation in stress relieved base metal for 10 h and above. Stress relieved weld metals showed no failure in these tests. The ECT technique was investigated in order to assess its suitability for the detection and quantification of sensitisation. The ECT results correlated very well with the findings of the ASTM Practice E tests. The eddy current (EC) amplitude increased with increasing DOS in both the as stress relieved and Strauss Tested conditions. The EC amplitude in as stress relieved condition was smaller than in Strauss Tested condition. This indicates that ECT holds promise as an on line monitoring tool for degree of sensitization (DOS) and IGC.