Gradients of structural-phase state of rail head after ultra long-term operation.

The structure and phase composition in differentially quenched 100-meter rails are studied after their ultra long-term operation (passed tonnage from 2013 is 1770 million gross tons) using the methods of modern materials science. The regularities of change in main parameters: the relative content of different morphological types of structure are revealed in cross-section of rails' head along central axis of symmetry and radius of fillet rounding at a distance of 0, 2, 10 mm from the surface. The stages of pearlite structure transformation of surface layer: the fragmentation of ferrite plates, fracture and dissolution of cementite plates, repeated precipitation of nanodimensional particles of carbide phase are traced. It is noted that transformations along central axis proceed slower against the change in rounding radius of fillet. [ABSTRACT FROM AUTHOR]