Effect of Arc Erosion under Different Currents on Wear Mechanism of Impregnated Copper Carbon Skateboard/Cr-Zr-Cu Contact Wire
The pantograph-catenary system of high-speed trains is composed of a pantograph and contact wires;this system is a key component of trains to power transmission.The probability of arc erosion occurring is greatly increased with the continuous rapid development of high-speed railways.Short-time offline between the carbon skateboard and contact wire is easy to produce an electric arc,and the offline arc will seriously burn the surface of the carbon skateboard and the contact wire,resulting in the attenuation and premature aging of the service life of the carbon skateboard.Few studies exist on the effect of different current-induced arc on the surface damage of the carbon skateboards.In this work,a reciprocating friction test was used to simulate the current-carrying sliding wear process of copper-impregnated carbon skateboards/contact wire.The arc was generated by adjusting the spacing between the carbon skateboard and the contact wire.The surfaces of the carbon skateboards were eroded by generating an arc at different strengths(30,40,60 and 80 A).As the intensity of the current increased,the offline arc energy impact intensity and the instantaneous temperature of the contact region were higher(above the 1 500 ℃).After arc erosion,Cu was greatly precipitated from the surface of the carbon skateboard and welded into a tumor,which formed an irregular sparse layer and extended cracks.Arc erosion caused the liquefaction and condensation of large amounts of copper particles in the contact area of carbon skateboards.After the arc erosion,the current-carrying friction test of the carbon skateboard/contact wire showed that the friction coefficient and the contact resistance both increased with the increased erosion time.When the erosion current were 60 A and 80 A,due to the deep erosion pit generated by the arc erosion,after the current-carrying friction test,there were still exit more arc erosion pits in the contact area of the carbon skateboard,and there were more contact"convex peaks"in the contact area,which was easy to produce stress concentration and leaded to continuous wear debris at the interface,this was also responsible for the sharply fluctuations of the contact resistance.The surface of the carbon skateboard was uneven due to arc erosion,and the temperature rises in the contact area were obviously(achieved 124.5 ℃)due to the fluctuation of the contact resistance.As the friction test proceed,the wear particles in the contact area were gradually increased,and the contact quality of the contact wire and the carbon skateboard continued to deteriorate.However,due to the gradual smoothing of the irregular area of the carbon skateboard/contact wire contact,the current path through the interface was increased.Therefore,the contact resistance had a downward trend in the later period of friction.The current-carrying wear mechanism and the different performances of the carbon skateboard/contact wire after arc erosion were revealed by SEM and 3D morphology analysis methods.The main wear mechanism of the carbon skateboard/contact wire were abrasive wear,oxidative wear,and spalling.According to the three-dimensional morphology analytic result,it found that the maximum wear depth of the carbon skateboard was increased with increasing erosion current(-328.96 pm for 80 A).This demonstrated that the strong arc energy caused serious damage to the uniform structure of the carbon skateboard surface and its wear resistance.
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