Electro-discharge Machining Performance of Ti–6Al–4V Alloy: Studies on Parametric Effect and Phenomenon of Electrode Wear

Abstract

In the present work, machinability of titanium alloy (Ti–6Al–4V) is examined during electro-discharge machining (EDM). Experiments are conducted by varying peak discharge current and pulse-on duration; the EDM performance is assessed in terms of material removal efficiency, and rate of tool wear. Surface integrity of the machined specimen is evaluated in purview of surface morphology and topographical features including surface roughness, surface crack density, white layer thickness, material migration, phase transformation, residual stress, and microindentation hardness. Effects of input parameters on EDM performance of Ti–6Al–4V are discussed. Phenomenon of tool wear during EDM operation is interpreted with carbide formation at the bottom surface of the tool electrode. Maximum material removal rate ($\sim 2.71\,\hbox {mm}^{3}/\hbox {min}$) is obtained at (${I}_\mathrm{p}=25\,\hbox {A}$, $\hbox {Ton}=200\,\upmu \hbox {s}$). Surface roughness of the EDMed specimen varies from 2.26 to $4.08\,\upmu \hbox {m}$. The lowest energy input (${I}_\mathrm{p}=6\,\hbox {A}$, $\hbox {Ton}=50\,\upmu \hbox {s}$) achieves minimum surface roughness (${R}_{\mathrm{a}}\sim 2.26\,\upmu \hbox {m}$). Microhardness values are found falling in the rage from 355.66 to 418.66 HV which is relatively more than ‘as-received’ parent material. White layers obtained in different parametric settings vary from 15.63 to $150\,\upmu \hbox {m}$). Higher energy input promotes formation of thicker white layer. Variation of surface crack density is observed within rage 0.000642 to $0.003369\,\upmu \hbox {m}/\upmu \hbox {m}^{2}$. Significant amount of C, Cu, and O immigration is detected through EDS analysis of the machined surface. EDMed surface along with bottom surface of worn out tool electrode are enriched with hard carbide layers.