The mechanical properties of the nanocrystalline layer on the surface of railway tracks

The mechanical properties of the nanocrystalline layer on the surface of railroad tracks were investigated using the indentation technique. It was found that its hardness reaches 14 GPa. The ultimate compression stress is in the range of 4–5 GPa, and the elastic limit is in the range of 2–3 GPa. The hot hardness decreases to 1 GPa at 630°C. An already existing nanocrystalline layer is unlikely to be plastically deformed as long as the rail–wheel contact temperature is below 150°C. If friction causes an increase in temperature above 500°C, plastic deformation of the surface layer accompanied by dynamic recovery is plausible. It is unlikely that the growth of the nanocrystalline layer is a consequence of a high temperature process.