Mechanism of Extremely Low Wear of an Electrically Conductive CVD Diamond Electrode for EDM

摘要

The performance of an electrically conductive CVD diamond thick film (called EC-CVD diamond) possessing a high thermal diffusivity has been examined as an electrode for fine electrical discharge machining (EDM). In order to investigate the possibility of using EC-CVD diamond electrode for micro EDM, its electrode wear was studied for the EDM of small areas. Furthermore, in EDM of tungsten carbide, a very low electrode wear ratio of 0.3% was realized with the EC-CVD diamond electrode compared to a wear ratio of 10% with the Cu-W electrode. One reason for the low wear of the EC-CVD diamond electrode may be an increased adhesion of graphitic carbon from the dielectric oil onto the electrode surface. To further investigate the mechanism of low wear of the EC-CVD diamond electrode, thermal analysis of the electrode and experimental verification were performed. The EC-CVD diamond electrode showed the lowest temperature rise compared to copper and graphite electrode materials, and this rise in temperature was lower than its graphitization temperature. Experimental results of electrode wear in de-ionized water are also in close agreement with the analyzed results and therefore it may be said that thermal diffusivity is also an important factor in the low wear of the EC-CVD diamond electrode.