Abstract
This paper deals with an investigation of new diamond-based composite electrodes for electrical discharge machining (EDM), which have similar EDM performances, lower cost and more flexibility in size and shape compared with an electrically conductive CVD (EC-CVD) diamond thick film electrode. The EC-CVD diamond thick film electrode with high thermal diffusivity was found, in the authors' previous study, to show very low electrode wear in finish EDM with a short pulse on time, compared with conventional copper and Cu-W electrodes. Among some diamond-based composite materials, it was found experimentally that, in EDM of a die-steel material and tungsten carbide material, a polycrystalline diamond (PCD) electrode shows a very low electrode wear ratio, similar to the EC-CVD diamond electrode, in a wide range of pulse on time of 1μs to 30μs and that the material removal rate of the PCD electrode is about 50% and 80% of the EC-CVD diamond electrode for die-steel and tungsten carbide, respectively. The results of the investigation of the reason behind the excellent EDM performance of the PCD electrode by FEM analysis suggested that the temperature rise of the electrode was restrained because of the high thermal diffusivity of the diamond in PCD and high electrical conductivity of the cobalt binder in PCD.
