Abstract
The sensitization resistance of the stabilized Type 347 (UNS S34700) stainless steels (SS) having different carbon and nitrogen contents was evaluated using the double-loop electrochemical potentiokinetic reactivation (DL-EPR) and ASTM A262, practice E methods. Samples were heat-treated to simulate the coarse grain region of the heat-affected zone (HAZ) during welding and subsequently aged at 948 K for different times. For comparison, DL-EPR tests also were conducted for the unstabilized steels, Type 316 (UNS S31600) and Type 304 (UNS S30400). For Type 347 SS, a criterion for sensitization in accordance with the ASTM A262, practice E test corresponded to a condition of > 10% reactivation ratio (peak reactivation current [Ir] /peak activation current [Ia]) from DL-EPR test. The carbon and nitrogen effects on the sensitization resistance of the Type 347 SS were explained in view of the observed microstructures. By introducing a resistance parameter based on the chemical composition, sensitization resistance of the stabilized Type 347 SS and the unstabilized steels was expressed as a unified function.