Effect of Temperature on Friction and Wear Behavior of 24CrNiMo Steel for High-Speed Train Brake Discs

A domestically produced 24CrNiMo low-alloy steel for high-speed train brake discs was taken as the research object, friction and wear tests were conducted at different temperatures （25, 200, 400, and 600 ℃）. The effect of temperature on friction and wear behavior of the test steel was investigated. The results show that after friction and wear at 25 ℃, the surface of test steel exhibited numerous deep and wide grooves with a large amount of wear debris, indicating that the wear mechanism was abrasive wear. After wear at 200 ℃, the grooves became shallower and narrower, the amount of wear debris decreased, and the effect of abrasive wear weakened. At 400 ℃, the number of grooves and wear debris further reduced, a thin and discontinuous oxide film formed on the surface, along with relatively large and deep spalling pits, suggesting that the wear mechanism transitioned to oxidation and adhesive wear. At 600 ℃, a continuous and dense thick oxide film formed on the worn surface, the depth and area of spalling pits decreased, and grooves and wear debris became even fewer; the wear mechanism remained primarily oxidation and adhesive wear. With increasing temperature, due to the formation of oxide films, the friction coefficient of the test steel during the steady-state wear stage decreased, and its fluctuation amplitude first decreased, then slightly increased when the temperature rose to 400 ℃, and decreased again when the temperature further increased to 600 ℃.. As the temperature rose, the wear rate decreased, with a diminishing reduction amplitude, indicating that the improvement of wear resistance.