Evaluation of toughness deterioration by an electrochemical method in an isothermally-aged N-containing austenitic stainless steel

This work presents the results of an evaluation of the deterioration of cryogenic toughness by means of an electrochemical method in a N-containing austenitic stainless steel (JK2) aged at temperatures of 700, 800 and 900 °C for times from 10 to 1000 min. The aging process at 700 and 800 °C caused the decrease in the Charpy V-Notch impact energy at − 196 °C because of the intergranular precipitation of carbides. Scanning electron micrographs of the Charpy V-Notch test specimens showed the presence of intergranular brittle fracture. The degree of sensitization was determined by the ratio of the maximum current density generated by the reactivation scan to that of the anodic scan, Ir/Ia, using the double-loop electrochemical potentiokinetic reactivation test. The Charpy V-Notch impact energy decreased with increase in the Ir/Ia ratio. This relation permits an estimate of the deterioration of cryogenic toughness due to thermal aging in this type of steel.