Effect of Rolling Direction Reversal on Friction and Wear Behavior of Wheel Steel

In order to improve the wear resistance of wheel steel in rolling contact conditions, friction and wear tests were conducted on a rolling-sliding wear test machine to measure the friction coefficients and wear rates of wheel specimens before and after their rolling direction reversal (RDR) at the transition and steady wear states. The surface damages of the wheel specimens were observed by scanning electron microscopy (SEM), and the deformed structures of the wheel specimens were observed by laser scanning confocal microscopy and SEM. The results show that the friction coefficients of the specimens were all around 0.495 before and after RDR, so the RDR has no effect on the friction coefficient of the friction pairs. After test, the wear rate of the wheel specimen whose RDR occurred at the transition state was 16.09 g/m, while the wear rates of the wheel specimens whose RDR occurred at the steady state were 13.65 g/m and 13.94 g/m, respectively, suggesting that the RDR at the transition wear state improves the wear resistance less than that at the steady state. For the wheel specimen with higher strain hardening rate before RDR, the depth of the wavy structure was shallower and the pearlite interlamellar spacing became smaller after wear test, and hence the wear resistance was improved more significantly.