Electron microscopy and electron probe microanalysis are used to estimate the distribution of carbon atoms in cementite particles and defective substructure elements at distances up to 10 mm from the running surface along the central axis and the symmetry axis of the gage corner of differentially quenched long 100-meter rails after a passed gross tonnage of 1411 and 1770 mln t. Three mechanisms of cementite plate transformation have been analyzed. Extremely long-term rail operation is shown to be accompanied by a significant redistribution of carbon atoms in the surface layers up to 10 mm thick. In the initial state, the main amount of carbon atoms concentrates in cementite particles; after extremely long-term rail operation, carbon is also located on structure defects (dislocations, grain and subgrain boundaries), in the surface layer, and in the α-iron-based lattice. An increase in the passed tonnage from 1411 to 1770 mln t is accompanied by more noticeable motion of carbon atoms to structure defects in the gage corner compared to the running surface. The results are discussed using the concepts of bifurcation interstitial structural states in crystal lattice rotation zones and the mechanism of plastic distortion, as well as an analogy between extremely long-term operation and megaplastic deformation.
Porfir’ev et al. (Thu,) studied this question.