Study On Rolling Contact Wear Properties Of Wheel-Rail Materials And Alleviating Methods

The rolling contact wear and fatigue of wheel/rail are more and more serious with the development of the high-speed and heavy-haul railway in China. The wear of wheel is aggravated because of the low hardness of the wheel materials, which was shown by the operation experience of the high-speed railway recently. So, the matching of wheel/rail materials and methods for alleviating the wear of wheel/rail were studied in this research, which is of great practical significance for alleviating the damage of wheel/rail and increasing economic benefits of railway transportation. The purposes of this study are to determine the optimal matching of wheel/rail materials and to evaluate the feasibility of methods for alleviating the wear of wheel/rail by the application of austempered ductile irons (ADI) wheel and the surface modification of wheel.The test materials are wheel materials (ER7, ER8-D2and ER8-D3) used for high-speed train and rail material (U71Mn). The carbon content of ER8-D2is the same with that of ER7with the alloy compositions changing, while the alloy compositions of ER8-D3are the same with those of ER7with the carbon content increasing. The differences of hardness and microstructure among the materials at different depths of wheel rim were analyzed. The rolling contact wear properties of the frictional pairs of wheel/rail were studied by using a MMS-2A testing apparatus under the condition of cooling and no cooling. The rolling contact wear properties of ADI materials and the surface-modification sample coupling with U71Mn samples were also studied. Conclusions are as follows.Based on the results of wear tests of high-speed wheels materials, it is founded that the wear of wheel/rail materials are alleviated when the frictional pairs are cooled. It’s suggested that the frictional pairs should be cooled under experimental condition, because that is closed to the operation condition. The wear behaviors of wheel/rail are mainly affected by the hardness of wheel materials. With the increasing of the hardness of wheel materials, the wear behaviors of the wheel materials are alleviated, while the wear behaviors of the rail materials are deteriorated. The wear properties of wheel materials are also affected by the chemical composition and microstructures to some extent. The coarse ferrite and high ferrite content have negative effects on the wear properties of wheel materials. To reduce the wear of wheel, ER8-D2wheel material is more suitable for high-speed wheel.The wear properties of two ADIs are improved significantly compared with that of the alloy wheel steel. The self-lubricating capability of the ADI with low hardness, small and large quantity distributed graphite nodule is excellent, and the wear resistance of the corresponding frictional pair is the best. The self-lubricating capability of the ADI with high hardness, large and small quantity distributed graphite nodule is weak, and the wear resistance of the corresponding friction pair is moderate. The alloy wheel steel is not self-lubricating, and hence the wear resistance of the corresponding friction pair is the worst.The durability of modification layer of the wheel sample treated by PIP+WPC duplex surface treatment is limited. The wear property of the wheel sample treated by laser roughing technology is improved significantly, while the wear behavior of the corresponding rail sample is aggravated dramatically. Therefore, these surface modification methods are not suitable for wheels.