Research on the relationship between microstructure and operational defects of wheels and rails
Authors:   Iron and Steel Institute of Z. I. Nekrasov National Academy of Sciences of Ukraine, Babachenko O. I. , Kononenko G. A. ,   Iron and Steel Institute of Z. I. Nekrasov National Academy of Sciences of Ukraine,   National Technical University "Dnipro Polytechnic", Podolskyi R. V. ,   Iron and Steel Institute of Z. I. Nekrasov National Academy of Sciences of Ukraine, Safronova O. A. ,   Iron and Steel Institute of Z. I. Nekrasov National Academy of Sciences of Ukraine, Shpak O. A. ,   Iron and Steel Institute of Z. I. Nekrasov National Academy of Sciences of Ukraine
Published: January 2025

The safety and economic feasibility of railway transport are largely determined by the reliability and efficiency of the wheel-rail pair. At the same time, the intensity of wear of elements and the rate of development of fatigue defects must be such as to ensure economically feasible operation of rolling stock and tracks. Operational reliability and durability of the wheel-rail pair is ensured by a rational balance of wear and wear resistance. Purpose: to analyze various types of operational defects that occur on the rolling surface of the wheel and rail head and to investigate structural changes in the area of occurrence of these defects. Material and research methods. The work involved an analysis of the microstructure in the working surface area of railway wheels and rails on which defects formed during operation. The studied wheels of grades 2, T were manufactured according to DSTU GOST 10791:2016; ER7, ER8 R8 – according to EN 13262:2020. Railway rails of categories R260Mn, R370Cr and U75 according to EN13674-1:2016. Research results. An analysis of the types of operational defects that occur on the working surface of the wheel rim and rail head was performed. It has been established that defects that form during operation are mainly associated with the accumulation of thermal and mechanical fatigue, wear of the wheel-rail contact surface, plastic deformation, and the appearance of sliders with the formation of martensite in areas subject to intense heat during braking. It is shown that contact fatigue during rolling due to the different distribution of the resulting force for rails, which are mainly subject to traction forces, and for wheels, which are more subject to braking forces, defects can manifest themselves to different degrees. Regarding defects of thermal origin, despite some differences found (different appearance of the burrs and structural differences in the metal in the area adjacent to the areas containing the specified defect), for different types of wheels and rails, the nature of the formation of the specified defect is the same. Wear resistance is primarily determined by the level of strength and hardness in the wheel-rail pair, while the wheel should be less wear-resistant. Conclusion. The initial structural state, chemical composition, level of mechanical properties and their uniformity depend on the production method and can affect the resistance to the formation of operational defects on the working surface of wheels and rails. To ensure rational and effective operation of railway transport, it is necessary to reasonably select a wheel-rail pair, taking into account the purpose of transportation, the level of hardness, the load, the speed of movement, the chemical composition and hardness of the metal of the wheel and rail.