Investigations of the structural components of rail joints, obtained by contact butt welding using burning-off, which are revealed on the surface of kinks after the destruction of the compounds during static bending tests and after destruction in operating conditions, were carried out. Analysis of the microstructure and chemical heterogeneity of the fracture surface was carried out with the help of a scanning electron microscope JEOL JIB-Z4500, equipped with an attachment for energy-dispersive analysis. The analysis showed that the main structural defects were poor penetration and inclusions of iron-manganese silicates that significantly reduced the parameters for mechanical tests of welded joints. Their presence in welded joints is unacceptable. Clusters of inclusions of aluminosilicates, so-called matte spots, and oxide films of a more complex composition are formed in the compound on the basis of non-uniformly distributed nonmetallic inclusions of the metal of the rail.

The structure, phase composition, and morphology of the surface layers of structural 1020, 1050, 1060 steels of the steel modified by the cathode spot of the welding arc are studied with the help of electron and optical microscopy. It is shown that the treatment of the cathode spot of the arc leads to grain refinement in the surface layer and causes its hardening. As a result of this treatment, partial or complete amorphization of the surface layer is possible.

Hardening of the side surface of the rail head with the use of optical and electron microscopy is studied. Results of industrial tests are given. Plasma hardening of the side surface of the rail allows one to obtain a favorable structure of the surface hardened layer (mixture of troostite, bainite and martensite) with a hardness of 450-830 HV and a thickness of the quenched layer of 2.5-3 mm. Thus, this significantly increases the service life of the rails due to the 2-3-time decrease in the wear rate of the side surface of the rail. The developed unit for plasma surface hardening of the rail allows performing qualitative surface hardening in width, depth and hardness of the surface layer of the metal. This equipment can be recommended for further pilot-industrial plasma surface hardening of the rail side surface in the conditions of the East Siberian Railway.

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