Wear and RCF damage behaviours of bainitic rail steels under low temperature environments

This study investigated the wear and RCF behaviours of a lath-like (1380B) bainitic rail steel and a granular bainitic rail steel (1250B) in low-temperature environments through rolling contact tests, using a pearlitic rail steel (U75VH) for comparison. Results showed that as temperature decreased, overall wear increased markedly, while average crack length and depth in all three steels became smaller. Among the steels, pearlitic rail steel consistently demonstrated the highest wear resistance and strongest resistance to crack initiation. At ambient temperature, lath-like bainitic rail steel performed better in resisting wear than the granular one; however, at -40 degrees C the opposite occurred, since the granular bainitic rail steel exhibited higher plastic deformation capacity. The lath-like bainitic rail steel also developed a few long cracks at low temperature. The superior lowtemperature wear resistance of granular bainitic rail steel was attributed to differences in transformation behaviour compared with lath-like bainitic rail steel. Furthermore, fragments generated from multi-layer cracks were observed in both bainitic steels under low temperature, caused by brittle fracture and subsequent extrusion and twisting of the material between cracks. In contrast, no such fragments formed in pearlitic rail steel, which retained relatively high plasticity even in cold environments and thus avoided brittle fracture. These findings highlight the distinct wear and RCF responses of rail steels of different microstructures, and reveal the temperature-dependent mechanisms governing their tribological performance.