Surface layer structure degradation of rails in prolonged operation

By methods of optical, scanning and transmission electron microscopy and microhardness measurement the transformation regularities of structure-phase states, defect substructure, fracture surface and mechanical properties of rail surface layer up to 10 mm deep in process of long-term operation (passed tonnage of gross weight 1000 mln. tons) were revealed. According to the character of fracture and level of structure imperfection the three layers were detected: surface, transition and boundary ones. It has been shown that the surface layer ~20 μm in thickness has a multiphase, submicro- and nanocrystalline structure and it contains micropores and microcracks. The increased density of bend extinction contours at 2 mm depth from the tread contact surface was noted, and it was shown that the maximum amplitude of stress fields was formed on the interphase boundary the globular cementite particle–matrix. The evaluation of stress fields was done.