Effect of cryogenically treated copper-tungsten electrode on tool wear rate during electro-discharge machining of Ti-5Al-2.5Sn alloy

Titanium, due to its excellent properties with high strength to weight ratio, is increasingly being used for various applications. Electric discharge machining (EDM), due to its unique features, is extensively used for machining of titanium and its alloys as it is difficult to machine titanium with conventional machining. EDM, however is most suited for electrically conductive materials and to make up for the poor thermo-electrical properties of Ti-5Al-2.5Sn titanium alloy, deep cryogenic treated (-184 degrees C) copper-tungsten (Cu-W) tool has been used in this study for machining. This study reports the effect of deep cryogenic treatment (DCT) on tool wear rate during electric discharge machining of Ti-5Al-2.5Sn titanium alloy by varying various process parameters namely cryogenic treatment of electrode material, peak current, pulse-on & off time and flushing pressure. Fractional factorial experimental design was used for designing the experimental study and the results were statistically analyzed to obtain optimal combination of input process parameters for minimizing tool wear. Peak current was observed to be the most significant process parameter in relative comparison to other input parameters. The results show a significant reduction in tool wear rate in case of DCT Cu-W electrode when compared to untreated Cu-W electrode. Surface characteristics of select Cu-W electrode and workpiece samples were analyzed using scanning electron microscope (SEM), energy dispersive spectrograph (EDS) and X-ray diffraction (XRD). Various chemical compounds specifically titanium carbide (TiC) were seen on both the machined and the tool surface due to material transfer during machining. (C) 2017 Elsevier B.V. All rights reserved.