Unveiling the environmentally assisted cracking behavior of rails in industrial railway applications and the strategies for improvement via vanadium-microalloying

Rail steel is prone to environmentally assisted cracking (EAC), which can cause severe rail breakage and endanger railway transportation safety. In this study, the stress corrosion cracking (SCC), a typical form of EAC, of a V-microalloyed pearlitic rail steel, U66, was explored in a 0.01 M NaHSO₃ solution through slow strain rate testing (SSRT) and constant load corrosion testing (CLCT). SSRT results indicate that U66 exhibits lower fracture elongation loss (15.16 %) and reduction in area (19.97 %) compared to U71Mn rail steel (28.96 % and 64.27 %, respectively). During CLCT, the SCC resistance of U66 increases approximately 32 % initially and reaches up to 41 % after 30 days. The improved performance of U66 can be attributed to the optimization of its microstructure and the incorporation of corrosion-resistant elements. These characteristics give U66 remarkable corrosion resistance impeding anodic dissolution induced cracking, as evidenced by its pore impedance of 356.40/Ω·cm², which is significantly higher than that of U71Mn (84.39/Ω·cm²). The increased density of hydrogen traps at grain boundaries, ferrite/cementite interfaces and nano-sized precipitates contributes to better resistance against hydrogen assisted cracking. These findings provide valuable insights for the development of high-performance rail steels and the improvement of railway infrastructure durability.