Effect of TiC in copper–tungsten electrodes on EDM performance

Abstract

EDM has been used extensively in the tool and die industry. The materials normally used in EDM electrodes are various types of copper, graphite, tungsten, brass and silver. Copper–tungsten (Cu–W) electrodes have been used widely to machine die steel and tungsten carbide work-pieces owing to the high thermal conductivity of Cu, and the better spark erosion resistance, low thermal expansion coefficient and high melting temperature of W. TiC is an extremely hard refractory material with a high melting temperature, and high thermal shock and abrasion resistance. The effect of the titanium carbide (TiC) in sintered copper–tungsten (Cu–W) electrodes on their EDM performance was investigated. Six batches of specimens with TiC content varying from 5 to 40% were fabricated by mixing, ball milling, pressing, and liquid phase sintering. The densification was improved by the addition of Nickel (Ni) due to the good solubility of Ni with Cu and W. The distribution of particle size became narrower with increasing TiC. A uniform dispersion of fine TiC particles in the Cu–W system and a narrower particle size distribution provide the possibility for obtaining dense electrodes. The relative density first increased and then decreased with increasing TiC while the electrical resistivity correspondingly first decreased and then increased. The tool material with added TiC showed good performance. The surface roughness decreased with the increase of relative density and vice versa. The highest relative density, lowest electrical resistivity, and best EDM could be obtained by 15% TiC addition, i.e. the lowest TWR, highest MRR and best surface finish.