Preparation Of C_f/C-Cu Composite And Investigation On Its Tribological Characteristics

Carbon/copper composites are known for their high electrical conductivity and good wear resistance. These properties lead to its application in electrical contact devices, such as electrical brushes and pantograph contact strips. In general, powder metallurgy is utilized to manufacture carbon/copper composites, but this has a number of disadvantages. It is difficult to prepare a carbon/copper composite with good interface bonding since liquid copper does not wet carbon, resulting in poor mechanical properties.To overcome the shortcomings of Carbon/Copper composite available nowadays, an attempt was made to prepare a novel C/Cu composite with an interpenetrating network structure. A carbon fiber knitted fabric reinforced copper (C/C-Cu) composite was fabricated by a spontaneous infiltration technique.. The C/C-Cu composite was fabricated by molten Cu alloy infiltration into a C/C preform with interconnection pores. The thermodynamics and kinetics of the infiltration process are studied. The microstructure, mechanical, electrical and tribological properties of the C/C-Cu composite were investigated.A thermodynamic model was established to calculate the interfacial tension between carbon phase and different copper based alloy. It is found that the Ti agent has a reduction effect on interfacial tension, thus achieving spontaneous infiltration.The Washburn model for spontaneous infiltration was used to analyze factors affecting the process. According to the theoretical analysis, higher Ti concentration in alloy, lager pore size of carbon preform and appropriate infiltration temperature and holding time were propitious to obtain good infiltration.The C/C-Cu composite formed an interpenetrating network structure. It was composed of Cu, TiC and C when the concentration of Ti is 10wt% in agent. The C/C-Cu composites exhibited high bending strength of 180?310MPa, excellent impact strength of 2.7?5.4J·cm-2 and particularly low electrical resistivity of 0.16-4.2??2·m.The thermal conductivity and CTE values of the composites decreased with increasing carbon content. The CTE values are much lower than that of carbon fiber reinforced copper matrix composite (Cf/Cu) and the predicted dates from the rule-of-mixture.The tribological characteristic of the composites was studied using the block-on-ring, pin-on-disk and reciprocating arrangements. It is found that the friction and wear properties of C/C-Cu composite are better under the reciprocating mode than the other two modes. As for reciprocating mode, a continuous debris layer is formed on the surface of C/C-Cu composites, therefore the friction coefficient and wear volume are maintained at low level.Under the block-on-ring mode, the friction coefficient and wear rate of the composites and the mass loss of Cu rings decrease with the increasing of density of the preforms; the friction coefficient and wear rate of the composite with resin carbon matrix is higher than those with pyrolytic carbon matrix; the wear rate of the composites with parallel orientation is higher than that with vertical orientation, while the formers' friction coefficient is lower.Under the pin-on-disk mode, the friction coefficient of the C/C-Cu composites decreases and wear rate increases with the increasing of electric current, and the wear of anode is larger than that of cathode, which may attribute to the chemical reaction on the interface; The friction coefficient and the wear rate both decrease with the increasing of the coupled-copper-disc's rotation speed. By the scanning electron microscopy, it has been found that the debris exist in the form of flake on the anode, and fine, loose and equiaxed on the cathode.A C/C-Cu brush with 37wt%Cu is fabricated and compared with the J201 brush with 50 wt%Cu. The wear loss, Rockwell hardness and density of the C/C-Cu brush are lower than that of the J102 brush; The energy dispersive X-ray analysis of worn surface of the brushes showed that there was less iron transfer cover onto the C/C-Cu than J201, indicating that the C/C-Cu brush did small damage to collector ring.