Use of eddy current testing method in detection and evaluation of sensitisation and intergranular corrosion in austenitic stainless steels

This paper deals with the applicability of eddy current testing (ECT) technique to assess and quantify sensitisation and intergranular corrosion (IGC) in thermally aged AISI type 316 stainless steel. Chemical and electrochemical tests specified by ASTM A262 Practices A and E (Strauss test) and G108, and ECT, were used to quantify degree of sensitisation (DOS). The DOS was categorised based on severity of the crack after bend test in increasing order as unaffected, fissured, cracked, and broken. The eddy current (EC) amplitude increased with increasing DOS in both the as-aged and Strauss tested conditions. The EC amplitude in as-aged condition was smaller than in Strauss tested condition. Empirical relationships were established between ECT amplitude and other DOS parameters.