Electrical Sliding Wear Of A1₂O₃/Cu Composite Used In Contact Wire

With the continuing development of high-speed electrified railway, the contact wire demands the copper alloy to have high electrical conductivity and mechanical properties, but also have excellent wear-resisting and high anti-softened properties. Al₂O₃/Cu composite has recently made their debut as potentially viable and attractive engineering materials for industrial applications that require high strength, high thermal- and electrical-conductivity, and high resistance to softening at elevated temperatures. Internal oxidation has been regarded as the most suitable method for Al₂O₃/Cu composite. This paper researches Al₂O₃/Cu composite with different A12O3-content prepared by internal oxidation. Based on the performance requirements by the high-speed railway on the contact wire material and strengthening mechanism of Al₂O₃/Cu composite, three materials containing 0.24wt%Al₂O₃, 0.40wt%Al₂O₃ and 0.60wt%Al₂O₃ separately prepared by internal oxidation were designed, and the electrical conductivity, hardness and tensile strength properties of the composite were tested. The tribological properties with and without current of Al₂O₃/Cu composite were investigated on self-made electrical sliding-wear tester. The influence of current, velocity and load on the wear rate of the composite were studyed by compareing with Cu-0.36Cr-0.06Zr. The morphologies of friction surface and vertical section of the composite were also examined with scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDS), and its abrasion mechanisms were discussed. The research is to explore the engineering applications on electric sliding field for providing theoretical basis about Al₂O₃/Cu composite.The following points are considered as the main conclusions:The Al₂O₃/Cu composites containing 0.24wt%Al₂O₃, 0.40wt%Al₂O₃ and 0.60wt%Al₂O₃ separately prepared by internal oxidation can obtain good integrated properties to meet the performance requirements of the contact wire, and the electrical conductivity reach 93%IACS, 89%IACS and 85%IACS, the tensile strength are 530MPa, 585MPa and 607MPa, and the micro-hardness are 152HV, 165HV and 178HV.The wear resistance of Al₂O₃/Cu composite is superior to that of Cu-0.36Cr-0.06Zr alloy under the same conditions, especially, 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu. The wear rate of all the materials under investigation increases with the increasing of current and sliding time under certain load. And the influence of current on wear rate is not obvious for 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu, while it is very notable for 0.24Al₂O₃/Cu and Cu-0.36Cr-0.06Zr. Moreover, the growth rate of wear rate of both 0.24Al₂O₃/Cu and Cu-0.36Cr-0.06Zr are higher than that of 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu. Besides, the service life of wear of 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu will appear in more and more superiority than the Cu-0.36Cr-0.06Zr alloy with the extending time during the electrical sliding wear processes. The wear rate of Al₂O₃/Cu composite decreases with the increasing of Al₂O₃-content under the same testing. Compared with 0.24Al₂O₃/Cu, 0.40Al₂O₃/Cu and 0.60Al₂O₃/Cu have higher wear resistance under the same conditions.The wear mechanism of Al₂O₃/Cu composite were adhesive wear and abrasive wear without current, while adhesive wear, abrasive wear, oxidation and electrical erosion would be the dominate mechanism under currents. The trend of adhesive wear would be serious with the increasing of current. The adhesions of Al₂O₃/Cu composite come from the copper-based powder metallurgy strip. By comparison, for Cu-0.36Cr-0.06Zr, the wear mechanism were the adhesive wear, abrasive wear and oxidation wear without current, while changed into adhesive wear, abrasive wear, oxidation and electrical erosion with current. Moreover, oxidation and electrical erosion were become more and more severe with the increasing of current.Based on the experimental study, Al₂O₃/Cu composite prepared by internal oxidation meets the performance requirements of the contact wire, and the Al₂O₃-content of Al₂O₃/Cu composite contact wire is 0.40～0.60wt%.