Rail strengthening in prolonged operation

In rail operation (with traffic corresponding to passed tonnage of gross loads of 500 and 1000 million t), the surface layer of the steel is significantly strengthened. Electron-microscope data permit quantitative analysis of the contribution of different mechanisms to rail strengthening in prolonged operation, at different distances from the contact surface. The strengthening is multifactorial: it involves substructural strengthening associated with nanofragment formation; dispersional strengthening by carbide particles; the formation of atmospheres at dislocations; and polar stress due to interphase and intraphase boundaries. The significant increase in the surface strength of rail steel after prolonged operation (passed tonnage of gross loads of 1000 million t) is due to the presence of long-range internal stress fields and to the fragmentation of material with the formation of nanostructure.