Effect of in-service work hardening on the sliding wear resistance of a heavy haul rail in the gauge corner

Abstract

This work evaluates the tribological behavior of three samples taken from a pearlitic steel rail with different hardness values (550, 450 and 370 HV0.1) due to the in-service work hardening effect. A pin-on-disc sliding wear test was selected to simulate the sliding wear conditions among the wheel flange and rail head corner and gauge face. The influence of the stress level was evaluated by varying the applied normal loads; the 50 and 500 N loads were associated with large and small radius curves, respectively. Pins were made from the rail samples, and the counter body (disc) used was H-13 steel (600 HV30). The mass loss was measured, and the coefficient of friction (COF) for each condition was calculated. Scanning electron microscopy (SEM) was carried out for microstructural characterization of the samples before and after the sliding wear test. The results showed a monotonic correlation between the superficial hardness and the sliding wear resistance under the low severity condition. The sample with the intermediate hardness (450 HV0.1) has the greatest sliding wear resistance under the low severity, 50 N condition, and under the high severity test condition (500 N). For the tests performed at 50 N, the wear facilitated crack propagation, and the preexisting cracks were removed from the pin (rail) interface. In contrast, for the tests performed with a 500 N load, the material removal rate did not overcome the crack propagation. In addition, the energy at the sliding interface was enough to promote a white etching layer (WEL), which reproduced the surface of the in-service rails, and the material removal was not sufficient to remove the cracks from the pin (rail) surface.