Experimental study on the wear and damage of wheel-rail steels under alternating temperature conditions

The objective of this study is to investigate the wear and rolling contact fatigue (RCF) damage of wheel and rail materials under alternating temperature conditions. Two series of rolling-sliding tests were performed: (1) at 20 degrees C for 75,000 cycles, and then continued at -40 degrees C for 10,000, 30,000, and 75,000 cycles, respectively; (2) at -40 degrees C for 75,000 cycles, and then continued at 20 degrees C for 10,000, 30,000, and 75,000 cycles, respectively. The results indicated that the decrease in the temperature would alleviate the wheel wear due to the formation of wear debris layer. Both the rising and dropping of the environmental temperature during the tests could lead to the increase in the rail wear. Besides, the decrease in the temperature could increase the plastic deformation and work hardening of wheel and rail discs. In addition, the crack initiation was correlated with the behaviour of plastic flow on the wheel. At 20 degrees C, long single cracks initiated and propagated along the highly deformed ferrite boundaries. At -40 degrees C, white-etching layer (WEL) was observed only on the wheel surface, which was mainly attributed to the severe plastic deformation. Then, the refined ferrites and WELs were the main crack initiation sources on the wheel.