Rotary Speed on the Current-carrying Rolling-sliding Friction and Wear Behavior of Copper-tin Alloy

Under long routing, high current and variable load, sliding friction leads to serious wear and poor stability of the pantograph-catenary contact tribo-pairs of electrified railway, which is one of the key factors restricting the development of rail transit. In this study, an innovative structural design of pantograph roller is proposed to transform the bidirectional sliding in current-carrying friction and wear problems into a two-dimensional composite friction motion of rolling and sliding, thereby reducing the reducing wear. However, most studies mainly focus on current-carrying sliding wear and current-carrying rolling wear under a single motion mode, and the researches on pantograph roller mainly focus on theoretical analysis and simulation research, and lack systematic investigate on current-carrying rolling friction and wear behavior, structural design and material matching. In this study, based on the analysis of the rolling-sliding motion relationship between pantograph roller and catenary system, the current-carrying rolling-sliding friction test system was developed, and the effect of rotary speed on the current-carrying rolling-sliding friction and wear behavior of copper-tin alloy was investigated. The innovative current-carrying rolling-sliding friction tester can accurately load normal loads, sliding and rolling speeds, and capture friction force and contact resistance in real time. The white light interferometer, OM, SEM, EPMA, and XPS were employed to evaluate damage zone, and the evolution curves of ECR and friction coefficient were analyzed to reveal the current-carrying rolling-sliding friction damage mechanism, and the wear reduction was discussed. The research results could provide data reference for controlling the wear of sliding tribo-pairs. The results showed that the ECR evolution of current-carrying rolling-sliding friction could be divided into four stages: initial ascend stage, descend stage, stable stage, and second ascend stage. The maximum ECR of the initial ascend stage was 35 mΩ, and the maximum ECR of the second ascend stage increased with the increase of the rotary speed. The friction coefficient curves could be divided into three stages: initial stage, ascend stage, and stable stage. The friction coefficient of stable stage was around 0.6~0.8. Compared with current-carrying sliding wear, rolling-sliding contact could significantly reduce wear loss, the maximum wear depth reduced from 130 μm to 6 μm, and the main damage mechanism changed from abrasive wear to delamination and oxidation wear. With the increase of rotational speed, the degree of material delamination and oxidation in the contact zone gradually increased and the surface roughness first decreased and then increased, the maximum surface roughness was 1.00 μm, and the CuO content in the damage zone increased.