Deformation strengthening mechanisms of rails in extremely long-term operation

Abstract

The quantitative estimation of strengthening mechanisms of rails’ surface layer is carried out on the basis of regularities and formation mechanisms of structure-phase states revealed by the methods of modern physical materials science. It is performed at different depth of rail head along central axis and fillet of differentially quenched 100-m rails after extremely long-term operation (gross passed tonnage of 1411 mln. tons). The contributions caused by the matrix lattice friction, intraphase boundaries, dislocation substructure, presence of carbide particles, internal stress fields, solid-solution strengthening of pearlite component of steel structure were estimated. It is shown that in the surface layer the main mechanism of strengthening is due to the interaction of moving dislocations with low-angle boundaries of nanometer dimensional fragments and subgrains. In a near-surface layer at a depth of 2–10 mm the main dislocation strengthening mechanism is due to interaction of moving dislocations with immobile ones.