Corrosion of worn out railway wheels

Purpose. It is necessary to study the conditions for the initiation of fatigue damages and the weakening effect of corrosion on the corrosion-fatigue wear of railway wheels. The aim of the work was to study the effect of the structure of wheel steel on the development of corrosion processes. Methods. To study the features of the development of corrosion damages in wheel steel the metal of worn wheels (1, 2; samples from the rolling surface, from the inner part of the rim body and from the disk) was used. Accelerated corrosion tests were carried out at room temperature in a special chamber in a humid atmosphere (relative humidity 80...83 %) containing 10 mg/m3 SO2, as well as NO and NO2, which is close to the effect of industrial atmospheres. Metallographic studies were carried out using a Neophot-21 microscope. Results. The features of wheel steel corrosion in different areas of worn out railway wheels are investigated. It is shown that the different corrosion rate of wheel steel is explained by its different structural state (degree of dispersion of pearlite, grain size, nature of the deformed structure). It was found that the rolling surface and the metal of the disc corroded faster than the metal from the center of the rim. Scientific novelty.The features of the mechanism and the rate of development of corrosion of wheel steel in different areas of worn out railway wheels during high-speed tests in an environment close to an industrial atmosphere are established. It is shown that the nature of the microstructure of wheel steel affects the corrosion rate. It is shown that in used wheels the rolling surface corroded faster than the metal from the central part of the rim, which is explained by the effect of stresses created by plastic deformation in a thin surface layer. It was found that the areas of the "white layer" on the rolling surface contribute to the slowdown of corrosion, which is associated with its ultradispersed structure. It was shown that the metal of the disk corroded faster than the metal from the central part of the rim due to the coarser ferrite-pearlite structure of the disk and the presence of ferritic banding.Practical significance.The use of the results obtained will allow developing anti-corrosion measures for railway wheels, which will prevent the formation of various types of defects during their operation.