Reciprocating wear mechanism of U75V flash-welded rail joints under the combined effects of chloride ions and ice

U75V rail steel has been used extensively in high-speed railway lines. The continuous cold and humid conditions along the Sichuan–Tibet Railway and variations in the coastal environment and temperature significantly affect the service life of the rails. However, research focusing on the wear behaviours of rail steels in low-temperature corrosive environments is inadequate. Hence, this study investigated the wear behaviours of U75V rail base material and welded joints in different solutions (0.9 wt. % NaCl and pure water) and at different temperatures (25 and 0 °C) using a reciprocating friction wear tester. The NaCl environment promoted oxide layer formation more effectively than the water environment, resulting in lower friction coefficients. Specifically, in the NaCl environment at 25 °C, the welded joint exhibited a lower wear rate, indicating enhanced wear resistance; however, the base material demonstrated better wear resistance than the welded joint at 0 °C. In pure water at 25 °C, the base material showed a lower wear rate than the welded joint, and at 0 °C, the welded joint exhibited a lower wear rate than the base material. The predominant wear mechanisms were abrasive, adhesive, and oxidative wear. These findings are expected to provide a sufficient basis for the optimisation of rail materials and maintenance strategies under complex service conditions.