Graphite particle size
Effect of graphite particle size on current carrying friction and wear behavior of C/Cu Composites
C/Cu composite material with copper with high conductivity and high thermal conductivity and good ductility, but also has graphite good lubricity, low expansion coefficient and the proportion of small features, so it has good electrical conductivity and thermal conductivity, wear resistance, arc erosion resistance performance and high strength and is widely used in all kinds of welding electrodes, electrical appliances engineering switch contact, generator collector ring, armature, rotor, electric locomotive pantograph etc.. This composite material is evenly distributed in the copper matrix graphite particles, metallic copper into three-dimensional reticular structure, graphite lubricant and anti welding effect. The traditional preparation process is the mixture of copper and graphite powder machinery and prepared by powder metallurgy method. Because of the poor wettability of copper and graphite, graphite / copper interface so that only the mechanical interlocking, low bonding strength, physical and mechanical properties of the materials to meet the application requirements, is the effective way to improve the surface treatment of graphite, namely copper coated graphite, graphite and copper matrix so as to enhance the interface, help to improve the mechanical and Tribological Properties of the composite material. At present, more research preparation and Tribological Properties of C/Cu composites, but the friction and wear mechanism analysis is not thorough and comprehensive, because the graphite particle size directly affects the microstructure of the composite and mechanical performance, and then affect the friction performance, so the research of graphite particle size effect on friction and wear behaviour of materials with important to the application of the material. In view of this, the C/Cu composites with 45 and 150 m graphite were prepared by cold pressing sintering powder metallurgy method, and the tribological properties and mechanism of the composites with different particle sizes were studied. The high pure natural flake graphite with particle diameter of 45 and 150 m was used to improve the wettability between copper matrix and graphite. After the surface treatment of graphite, such as roughening, sensitization and activation, electroless copper plating was carried out, and the graphite particles were cleaned by distilled water after copper plating. The copper coated graphite powder 45, 150 m respectively with a particle diameter of 75 mu m electrolytic copper powder (99.9% purity) were in accordance with the ratio of graphite 10wt%, fully mixing powder into two groups, pressed into the blank in 380MPa, sintering in hydrogen reduction atmosphere protection of bell-jar furnace in molding process, the sintering temperature is 850 to 860 DEG C, insulation 1h. The final processing of phi 9mm * 25MM pin. Test on pin to disc current carrying friction and wear tester. Pin sample material is C/Cu composite material, disk sample material is QCr0.5 copper alloy. AC constant current power supply is used as test supply, current is 50A, sliding speed is 5, 10, 20, 30m, s-1, load 30N, test time from 10 to 20s.
45 m graphite particles of less than 150 m graphite particles can reduce the occurrence of C/Cu composite arc, and can significantly improve the current carrying friction environment. Small graphite particles can improve the mechanical properties of C/Cu composites and enhance the formation of friction surface lubrication, thus effectively reducing the friction coefficient and wear rate of composites.
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