SCC behavior and susceptibility prediction mode of SMA490BW weathering steel under cathodic potential

Abstract

SMA490BW weathering steel has been used to manufacture high speed train bogie structures. However, its stress corrosion cracking (SCC) behavior was not very clearly, let alone the prediction mode. In this work, combined with fracture surface analysis by SEM, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization analysis, the SCC behavior of SMA490BW steel in 3.5 wt.% NaCl solution under cathodic potentials from open circuit potential (OCP) to −1200 mVSCE (SCE = saturated calomel electrode) was studied using slow strain rate tensile (SSRT) method at 25 °C. The results indicated that the SCC susceptibility index (ISSRT) decreased with the applied potential negative shift from OCP (ISSRT = 0.31) to −800 mVSCE (ISSRT = 0.11) by anodic dissolution (AD) mechanism, and then sharply increased with the potential negatively increasing (ISSRT = 0.41 at −1200 mVSCE) by hydrogen embrittlement (HE) mechanism. The SCC susceptibility could be preliminarily predicted using the mode founded as a function of charge transfer resistance (Rt): This study will be helpful for the service assessment of high speed train bogie structure and other structures manufactured by SMA490BW steel.