Formation of Gradient Structure–Phase States in the Surface Layers of 100-m Differentially Quenched Rails

Abstract—The evolution of the structural-phase states in the surface layers of the head of differentially quenched DT350 rails to a depth of 10 mm are studied by optical microscopy and transmission electron diffraction microscopy along the central axis after the passage of a tonnage of 691.8 mln t gross in the experimental ring of AO VNIIZhT (proof ground for railway transport). The formation of a gradient structure is revealed. In this structure, the scalar and excess dislocation densities, the lattice curvature–torsion amplitude, and the degree of deformation-induced transformation of lamellar pearlite change gradually. The mechanisms of fracture of cementite lamellae are considered.