A study of the material removal mechanism of polycrystalline diamond in electrical discharge machining based on spectroscopic measurement

This paper describes the spectroscopic measurement of arc plasma temperature and the radiation lines of different atoms in an electrical discharge machining (EDM) process under different controlling parameters: discharge current, voltage, and pulse width. The radiation lines of W, Co, and C were calibrated, and the intensities of these radiation lines, which increased with increasing discharge energy, represented the electrode wear and the material removal rate. It was found that the electrode wear and plasma temperature increased seriously with increasing discharge current, but a low electrode wear rate and high machining efficiency were obtained because of the low intensity of the radiation line of Cu and the high intensities of the C and Co lines resulting from increasing impulse width. The plasma temperature was calculated by the line-pair method, and the temperature was in the range of 5132–7758 K, which is higher than the gas/solid transition temperature of diamond at normal pressure and temperature. The results showed that some parts of the diamonds were directly transformed to a gaseous state by the high temperature generated by the discharge in the EDM process; the white layer, which consisted of some metals, covered the surface of the diamond.