Effect of lubrication on wear behaviour of a medium carbon and high silicon carbide-free bainitic steel

This study evaluates the wear behavior of a carbide-free bainitic steel through ball-on-disk wear tests in dry conditions and in lubricated ones similar to those occurring in the wheel flange-rail gauge contact. Three environmentally adapted greases were selected, together with two commercial products specifically designed for railway lubrication systems. Before wear tests, microstructure and mechanical properties were assessed by scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), roughness and microhardness (HV0.5) measurements. The coefficient of friction was directly provided by the equipment, whereas the wear rate was determined by the wear volume. Wear tracks were analyzed by SEM/EDS, XRD and HV0.5 tests. Based on the results, adhesion and tribo-oxidational wear were both active in dry conditions. The best performing lubricants were those that limited oxidation of steel more effectively. In all dry/lubricated conditions, a layered microstructure was detected in the sub-surface regions of the wear tracks. In these regions, increase in the mean values of compressive residual stresses and microhardness confirmed the occurrence of plastic deformation and transformation-induced plasticity effect.