Structure, Phase Composition and Properties of Rail Running Surface at Extremely Long Operation Time

The paper presents investigations of the structure, phase composition and properties of the rail running after bulk steel hardening. Investigations are performed at a different depth by using modern techniques of material physics in extremely long operation conditions (gross weight of 1411 million tons). The Rockwell hardness measurements at a depth ranging from 2 to 10 mm, show a decrease in the hardness level from 37.1 to 35.8 HRC and in the microhardness – from 1481 to 1210 MPa, respectively. The multiple modifications of the rail running surface include the disintegration of lamellar perlite and the formation of the submicron size subgrain structure varying between 100 and 150 nm; the formation of 30–55 nm carbide phase nanoparticles on the grain boundaries and in the subgrain volume; the growth in microdistortions and the crystal lattice parameter of the α-Fe solid solution; the increase in the scalar dislocation density. Possible reasons of these changes are discussed herein.