Effects of Tool Electrode on EDM Performance of Ti-6Al-4V

Due to widespread application of Ti-6Al-4V especially in automotive, aerospace, defense, and biomedical industries; machinability of this alloy is of immense importance. Very low thermal conductivity of Ti-6Al-4V is mainly responsible for its poor machinability. During Electro-Discharge Machining (EDM), conductivity of the workpiece as well as electrode plays a vital role affecting process performance. In this context, choice of electrode also influences the machining efficiency. Therefore, selection of an appropriate electrode to enhance performance of EDM on Ti-6Al-4V alloy is indeed necessary. In the present reporting, an experimental work has been carried out to investigate ease of machining of titanium alloy (Ti-6Al-4V) for electro-discharge machining using Tungsten and Copper (normal and cryogenically treated) electrodes. Experiments have been performed at different values of peak discharge current to study EDM performance on Ti-6Al-4V in terms of material removal efficiency, surface roughness, surface crack density and white layer thickness observed for the EDMed end product prepared from Ti-6Al-4V work material. Influence of peak discharge current on topography of the EDMed work surface has been examined. EDS analysis followed by micro-indentation hardness test has been performed to examine the extent of carbon enrichment onto the machined surface during EDM operation. XRD tests have been carried out to comprehend metallurgical aspects of the EDMed work surface which are supposed to be affected by the thermo-electrical phenomenon of EDM operation. Results obtained thereof, have been analyzed in detail to understand effects of electrode in persuading machinability of Ti-6Al-4V while machining though EDM route. It has been found that among three tool electrodes selected (Tungsten, normal Copper and cryogenically treated Copper), cryogenically treated Copper electrode has been found the most superior in purview of EDM performance.