Evaluation of Mechanisms for Strengthening of Surface Layers of Long Rails in Different Directions Under Continuous Operation

The structural-phase sates and defect substructure are studied by the method of transmission electron microscopy using diffraction at different distances from the wheel–rail contact surface along the central axis of symmetry of the top of rail (TOR) (rolling surface) and along the radius of rounding (fluting) of the differentially hardened rails of the DH400RK category made of hypereutectoid steel after their continuous service. Using the obtained structure parameters, the estimates are made of the hardening mechanisms (strengthening by pearlite component, incoherent cementite particles, grain- and subgrain boundaries, dislocation substructure and internal stress fields) controlling the yield stress in the steel under study. A comparison is performed of the quantitative fine structure parameters and the contributions into hardening on the rolling surface and fluting. It is found out that the prevailing morphological component near the wheel– rail contact surface is the subgrain structure, and in the fluting – strengthening by incoherent particles.