Surface gradient structure-phase states formation under differentiated quenching of 100 meter rails

Using transmission electron microscopy methods the layer by layer analysis of rails differentially quenched in different regimes is carried out on different scale levels. It is shown that the differentiated quenching of rails is accompanied by the formation of morphologically different structure, being produced according to the diffusion mechanism of γ-α transformation and consisting of plate perlite grains, free ferrite grains and grains of ferrite-carbide mixture. The gradient character of the changing of structure, phase composition and dislocation substructure parameters in the surface layer of rails head is established. It is revealed that the interfaces between globular cementite particles-matrix are the most dangerous stress concentrators.