Аннотация
Abstract To determine the optimal range of hardness of the wheel rim strengthened layer and the rail head rolling surface, which provides an increase in wear resistance, the variants of hardness of the wheel-rail friction pair are studied. On a machine MI-2 in laboratory conditions, a pair of cylindrical roller-insert was tested under sliding friction. Hardness of wheel steel samples varied from 275 to 900 HVw. Samples of R65 rail steel were used as a counterbody, the hardness of which was in the range of 345–455 HVr. The hardened layer depth for wheel steel samples is ~1 mm. At the same time, the wheel–rail pair hardness ratios were chosen, which can be obtained in real rolling stock operating conditions, which brings the laboratory tests closer to production ones and is of practical importance. It is shown that the optimal range of wheel hardness is in the range of HV 557–672, i.e., the required wheel and rail hardness ratio HVw/HVr is in the range of 1.41–1.58. An increase in wheel hardness above 860–900 HV under actual operating conditions can lead to hardened layer spalling and cracking, as well as to intense rail wear. Hardening of rim and wheel flanges to a relatively low hardness of 275–505 HV is ineffective, since wear resistance improves slightly. It is noted that the results of laboratory tests and the expressed considerations on the optimal ratio of hardness of the wheel-rail friction pair to increase their wear resistance should be confirmed in the operating conditions.