Acoustic emission monitoring of stress corrosion cracking

Abstract Acoustic emission (AE) measurements have been made for anodic-dissolution-, cathodic-hydrogen- and gaseous-hydrogen-induced subcritical crack growth. Measurements have been made on iron with segragated phosphorus and silicon, nickel with segregated phosphorus, type 304 stainless steel heat treated to produce high and medium degrees of sensitization and a tool steel. Intergranular fracture was the primary crack extension mode; however, the event rate per unit of crack extension correlated with the fraction of transgranular fracture. Emission from ligament fracture behind the advancing intergranular crack front is thought to be the source of the AE. These results suggest that AE could potentially be useful for life prediction of components susceptible to environment-assisted crack growth, although the results are very preliminary and need further substantiation.