Formation and evolution of structure-phase states in rails after drawn resource

Abstract

By optic and transmission electron microscopy, the regularities of the transformation of structural-phase states, the defective substructure of the rail surface layer to the depth of 10 mm under long-term operation (passed gross tonnage 500 and 1000 mln ton) are determined. In the initial state the structure is presented by perlite grains with predominantly lamellar morphology, grains of a ferrite-carbide mixture and structurally free ferrite grains. It is shown that operation of rail steel is accompanied by a complete failure of lamellar pearlite grains in the 15 μm thick surface layer and the formation of a ferrite-carbide mixture with nano-size particles. The strain-induced transformation of steel leads to the increase in the scalar and excessive density of dislocations, the curvature-torsion value of the crystal lattice and the amplitude of internal stress fields.