| For Cu-Mo- WC composites, the copper substrate can provide good conductivity,the high melting point of molybdenum can increase the welding resistance, the doped tungsten carbide particles maintains the performance of superior electrical and thermal conductivity of copper matrix but also improve their strength and high-temperature stability. In recent years, the research of the new electrical contact materials such as the Cu- Mo- WC composite has been focused, both in China and abroad.The electrical contact composites(Cu- Mo)- WC- 0.5% LaCl3 with different content of WC in this paper were prepared using the SPS discharge plasma sintering process. The properties of above materials such as electrical conductivity, density,relative density and microhardness were measured respectively. The microstructure was also analyzed. The influence of WC content on the microstructure and properties of the composites were also analyzed.Meanwhile, the Gleeble-1500 D thermal- mechanical simulation testing machine was used for the isothermal compression experiment, and then the constitutive equation of the composites were established by determining the thermal deformation activation energy. The friction and wear test of the composites were performed in a UMT- 2 multifunctional friction and wear testing machine to study the influence of WC content on the tribological properties of the composites. The JSM-5610 LV scanning electron microscopy was used to observe the wear surface morphology. The wear mechanisms were also analyzed briefly. Using the JF04 C electric contact testing system, the electrical contact performances of the composites were investigated. The mass transfer and transfer direction under the test condition of the DC resistance were also studied respectively. And then the surface morphologies of the composites after the arc erosion were also investigated using a scanning electron microscope and the arc erosion mechanisms of the composites were discussed in brief.The experimental results showed that,(1) all of the six kinds of prepared composites are relatively dense, the relative density of the composites are 87.8 ? 94.0%. The WC particles uniformly distributed in the copper substrate which have a dispersion strengthening effect. The electrical conductivity are 29.4%IACS, 31.6% IACS, 28.7%IACS, 26.1% IACS respectively. And the electrical conductivity increases at first then decreases with the increase of WC content. The microhardness of the composites are95 HV, 128 HV, 109 HV, 113 HV respectively, and the microhardness increases with the increasing of WC content.(2) The high temperature rheological stress-strain curves of the Cu-Mo-WC composites have the typical characteristics of dynamic recrystallization. And the peak stress increases with the increasing strain rate or reducing deformation temperature. Meanwhile, the thermal deformation activation energy is calculated and the high temperature deformation constitutive equation of composites is established.(3) Under the experimental condition, with the increase of WC content the wear rate of the composites has a downward trend while the friction coefficient of the composites has an increase trend. The wear mechanisms of the composites are mainly in the form of abrasive wear.(4) When the current is 20 A, there are no obvious material transfer occurred, while some degree mass loss are observed both in cathode and anode; When the current is above 20 A, the material transfer from cathode to anode obviously occurred, and the amount of material transfer increases with the increase of current. After arc erosion the contact surface morphologies present such features such as pores, melting pools and pits, which become obvious with increasing the test current. While the contact resistance gradually decreases with increasing current. And for the contact resistance and welding force, there is no obvious fluctuation with the current changing. |
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