Formation of Gradient Structure in Rails at Long-Term Operation

Abstract

It has been shown by the methods of physical material science that long-term operation of rails is accompanied by the formation of the gradient structural constituents consisting in the regular change in relative content of lamellar pearlite, fractured pearlite and structure of ferrite-carbide mixture in cross-selection of rail head. As the distance to the surface of rails increases the relative content of metal volume with the structure of lamellar pearlite decreases and that with the structure of fractured pearlite and ferrite-carbide mixture increases. It has been established that the characteristic feature of ferrite-carbide mixture structure is a nanodimentional range of grains, subgrains and particles of the carbide phase forming it. The dimension of grains and subgrains forming the given type of structure varies within the limits of 40-70 nm. The size of carbide phase particles located along the boundaries of grains and subgrains varies within the limits of 8-20 nm.

Keywords:
gradient structure; transmission electron microscopy (TEM); carbides; nanostructured materials; pearlitic steels