SYNTHESIZING AND EVALUATION OF NEW COPPER-TUNGSTEN BASED EDM ELECTRODE FOR MACHINING HARDENED MATERIALS

By using Electrical discharge machining (EDM) it is possible to machine any materials that are difficult to machine by using conventional machining technique as long as it is electrically conductive. The performance of EDM is highly depending on the type of electrode being used, the power supply system, and the dielectric system. Copper-Tungsten electrode is the higher in wear resistance but it is difficult to manufacture due to variation of melting point and zero miscibility of copper (Cu) with Tungsten (W). Thus, new modified Copper-Tungsten electrodes were synthesized taking into consideration the variety of melting point and zero miscibility. Ball milling was used to synthesize the new electrode material and Taguchi method is used to design and analyse the experiment. Material removal rate (MRR) and electrode wear (EW) are the main parameters used for testing the performance between the existing Copper-Tungsten (Cu-W) electrode and the new developed electrode. Machining variables selection show that the gap voltage, peak current and pulse on time are the most important ones that contribute on material removal rate, electrode wear and surface roughness (Ra). Results of milling process indicate a clear change in the thickness of crystalline and d-spacing of the milled powder after five hours milling time. The performance of Cu-WC-Si electrode shows an improvement in MRR by an average of 22.5% when milled for 5 to10 hours. The EW of 10 to 20 hours milled Cu-WC-Si improved by an average of 62 % from that achieved by using Cu-W electrode. The performance of Cu-WC-Ti and Cu-WC-Ti-Si electrode show clear improvement in the electrode wear but at the expense of MRR. It is reduced by an average of 86% for Cu-WC-Ti and by 70.1% compared with that achieved by using Cu-W electrode. Si additive improve TWR of Cu-WC-Si electrode where it shows the lowest TWR (10%) compared with that achieved by Cu-WC-Ti (466%) and Cu-WC-Ti-Si (37%). The contribution of milling variables on the performance of the new developed electrodes shows that milling time is the most important variable.