Experimental Investigation of Machinability and Surface Characteristics in Microelectrical Discharge Milling of Titanium, Stainless Steel and Copper

Microelectrical discharge milling (µED-milling) possesses good processing capability to fabricate intricate shapes in any electrically conductive material. In the present work, an experimental study is carried out to investigate machinability and surface characteristics of titanium (Ti) grade 2 alloy, stainless steel 304 (SS304) and copper (Cu) undergoing microelectrical discharge milling (µED-milling) process. Voltage, feed rate (FR) and tool rotation speed (TRS) are the process parameters that are varied during machining. The response measures chosen for evaluating machinability performance are material removal rate (MRR) and tool wear rate (TWR). After performing µED-milling, topography of the fabricated microslots is characterized by optical microscopy, scanning electron microscopy and surface roughness (Ra) analysis, whereas material composition analysis is carried out by X-ray diffraction and energy-dispersive X-ray techniques. It is found that Cu exhibits higher MRR than Ti and SS304, whereas SS304 exhibits higher TWR than Ti and Cu at all the chosen parametric conditions. The most significant parameter affecting MRR and TWR as ascertained by analysis of variance is FR, followed by voltage and TRS. Surface morphology of the microchannels fabricated by µED-milling reveals that globule formation and redeposition phenomenon is profound in case of Cu and SS304. In contrast, Ti grade 2 exhibits better surface morphology in terms of less globule formation, microvoids, redeposition layer and lower Ra as compared to Cu and SS304.