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

The mechanical properties of the nanocrystalline layer on the surface of ra ilroad tracks were investigated using the indentation technique. It was fou nd 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 degreesC. An already existing nanoc rystalline layer is unlikely to be plastically deformed as long as the rail -wheel contact temperature is below 150 degreesC. If friction causes an inc rease in temperature above 500 degreesC, plastic deformation of the surface layer accompanied by dynamic recovery is plausible. It is unlikely that th e growth of the nanocrystalline layer is a consequence of a high temperatur e process. (C) 2001 Elsevier Science B.V. All rights reserved.