| As sliding-collecting-current materials，Cu alloy-matrix self-lubricating composites have been widely used in electric locomotives and rail transit vehicle. Preparation of new sliding-collecting-current materials and studying their current-carrying tribological properties can provide references to develop the material of grounding device which ensures the safety of train operation. In this paper, different SiC particles reinforced copper-matrix self-lubricating materials were prepared by powder metallurgy method. The effects of SiC content and particle size on microstructure, physical properties, current-carrier friction abrasion were studied. The changes of the wear mechanism of composites under current-carrying conditions were investigated. The influences of friction velocity and current density on arc rate and current-carrying efficient were also researched. Graphite and SiC particles treated with copper plating were used to prepare the composites plated by copper. The microstructure and properties of composites plated by copper and those unplated by copper were compared. The main research results are as follows:The composites prepared by different mass fraction of15μmSiC particle show that the particles mainly distribute in the Cu matrix when there is a low SiC content, and that the particles tend to distribute in C/Cu interface with the increases of SiC content. Meanwhile, the increase of SiC content leads to a decrease of material density and conductivity, and a increase of hardness and porosity. During the tests of current-carrying sliding friction, the friction coefficient rises and the mass wear rate first falls then goes up.2%SiC/C/Cu composite has the lowest wear rate.At the mass fraction of2%, SiC particles existing in the composites prepared by7.5μm or15μm particles not only dispersively distribute in the copper matrix, but also in C/Cu interface of the composites. While the SiC particles are embedded in or completely coated by the copper matrix of the composites with25μm or40μm particles. With the increase of particle size，the porosity of composites decrease. Correspondingly, the density，hardness and conductivity increase. The tests of current-carrying friction and wear show that the increase of particle size causes friction coefficient and the mass wear rate of composites first falls then goes up.25μmSiC composites have the lowest friction coefficient and wear rate.Both the friction coefficient and wear rate of composites rise as velocity increases. The wear mechanism of composites mainly is abrasive wear. When the velocity is faster than25m/s, arc erosion shows. The friction coefficient reduces and the wear rate rises as the current density increases. The wear mechanism of composites mainly is arc erosion and abrasive wear.The arc rate is associated with the condition of friction surface and current density. The current-carrying efficient is seriously affected by the condition of friction surface and the arc rate. The higher arc rate is, the lower current-carrying efficient will be. The arc rate first rises slowly and the current-carrying efficient rises as the velocity increases. When the velocity is faster than25m/s, the arc rate goes up sharp the current-carrying efficient falls rapidly. With the increase of current density, the arc rate increase and the current-carrying efficient decrease gradually.The copper plating of the graphite and SiC particle improves the poor wetting of C/Cu interface and SiC/Cu interface. The graphite particles are tinier and more dispersively distributed in the composites with particle copper plating. The composites with particle copper plating express better matrix connectivity than those without particle copper plating. The porosity of composites with particle copper plating is apparent lower than those without copper plating. In contrast, the density, hardness and conductivity are higher. |
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