Stress corrosion cracking behavior and mechanism of high manganese steel in inshore SO₂-polluted marine environment

High manganese steel (HMS), widely utilized in railway transportation, often encounters the compounded challenge of high stress impact and corrosion, ultimately leading to environmentally assisted cracking. To comprehend this phenomenon, we delved into the stress corrosion cracking (SCC) behavior and mechanism of HMS in a SO₂-polluted marine environment, employing both slow strain rate test (SSRT) and constant load U-bend test (CLUT). By comparing the SCC behavior in three distinct test solutions: 0.01 M NaHSO₃, 0.01 M NaHSO₃ with 1 wt% NaCl, and 0.01 M NaHSO₃ with 3.5 wt% NaCl, we discerned the varied influence of Cl⁻ and SO₂ on SCC. Analyzing the stress–strain curves from SSRT and the cross-sectional crack morphologies from CLUT provided insights into the SCC susceptibility of HMS in these solutions. Notably, the SCC susceptibility in 0.01 M NaHSO₃ exceeded 40%, while in the solution containing 3.5 wt% NaCl, it significantly surpassed 65%. Further examination, including an analysis of the rust layer’s elemental distribution and phase composition, electrochemical testing of the rust layer, and an assessment of corrosion morphologies on the base metal, revealed the relative contributions of various corrosive media to SCC. This comprehensive study not only sheds light on potential SCC mechanisms but also offers valuable insights for evaluating the service life of HMS and identifying areas for performance optimization of this critical high manganese steel alloy.