Tribological properties of the surface of railway tracks, studied by indentation technique

The tribological properties of the surface of railway tracks have been studied taking into account that the surface layer is composed of sublayers with different microstructures and mechanical properties. The tribological properties of the sublayers have been investigated both in the dynamic and static loading mode. The topmost sublayer is characterized by a very high hardness and the yield stress value of 3.2 GPa. It also has low plasticity. It was shown that as long as the layer is continuous it has high wear resistance in tribological tests. However, its fracture reduces the wear resistance considerably and increases the friction coefficient. Wear of the surface layer exposes subsequent sublayers to friction, so that the tribological properties of the rail track change during the wear process. The tribological properties of the top layer are similar for both the dynamical and static loading, while the tribological properties of the subsurface layers are sensitive to the loading mode.