Characterization of the Microstructure Changes Induced by a Rolling Contact Bench Reproducing Wheel/Rail Contact on a Pearlitic Steel

Understanding the effects of wheel-rail contact on the microstructure of rails is an important issue for railway management. The impact of wheel-rail contact and surface preparation on the microstructure of rails is studied using a rolling contact bench. Microstructure changes are characterized by coupling microhardness measurements and scanning electron microscopy combined with electron backscattering diffraction. This analysis led to a complete description of the sub-surface microstructure in link with the contact conditions. It was found that the use of a corroded layer on the material surface led to a considerable strain-hardening decrease. Lower surface strain-hardening was also found for sliding conditions compared to pure rolling conditions. EBSD characterizations using different indicators highlighted the importance of the scale of investigation: the use of Kernel Average Misorientation led to the identification of larger impacted depths than the Inverse Pole Figures.