STAGES OF CEMENTITE DESTRUCTION IN HYPEREUTECTOID STEEL RAILS DURING LONG-TERM OPERATION

10.25712/ASTU.1811-1416.2026.03.001

Abstract

Using modern physical materials science methods (optical, scanning and transmission diffraction electron microscopy, and X-ray diffraction analysis), an analysis of the mechanisms and stages of failure of lamellar pearlite at distances of 10, 2, and 0 mm from the surface along the fillet radius of the rail head made of hypereutectoid steel after long-term operation on the East Siberian Railway (carried tonnage of 175.9 million gross tons) was performed. The characteristics of two possible failure mechanisms of cementite laminae were identified: deformation-induced (cutting by sliding dislocations) and non-diffusion-induced (transition of carbon atoms from the cementite lattice to dislocations). A comparison of the features of the failure mechanisms of cementite in rails made of hypoeutectoid steel was conducted. It is shown that during the final stage of structural-phase state and defective substructure evolution preceding failure, a subgranular structure based on a solid solution of the α-phase with nanosized particles of the carbide phase distributed along the subgrain boundaries forms within the pearlite grains, thereby forming globular cementite. Potential avenues for extending rail service life are outlined based on an analysis of contact fatigue failure mechanisms under extreme operating conditions on the East Siberian Railway.