Influence of Electrode Cooling on Recast Layers and Micro Crack in EDM of Titanium

Abstract

Electrical discharge machining (EDM) process is a manufacturing method for shaping hard metals and formation of deep and complex shaped hole by spark erosion in electrical conductive materials such as metals, metallic alloys, ceramics etc. EDM process is achieved by a series of recurring electrical discharges between the electrode and workpiece in the presence of dielectric fluid. EDM unique feature of using thermal energy to machine conductive materials irrespective of material hardness has been its major advantage in the manufacture of aerospace, surgical, mould, die, automotive and as well as sport components. The effectiveness of EDM process depends among other factors on the thermal properties of the electrode material. The objective of this study is to study the influence of electrode cooling on recast layers and micro crack in EDM of titanium. The machining parameters investigated in the present study are current intensity (I), pulse on-time (Ton), pulse off-time (Toff) and gap voltage (V), which are of great interest for EDM researchers. The copper electrode is used to EDM titanium workpiece at room temperature and at sub-zero temperature using liquid nitrogen. The influence of cooling of copper electrode on recast layers and micro crack on titanium were investigated using scanning electron microscope (SEM) and has been reported in this study.

An Experimental Study on Electrosparking of Tool Electrode Forced Cooling Based on Micro Heat Pipe Bundle

“…On this basis, the goal of improving electrosparking stability, processing precision and surface quality can be realized. Existing studies have demonstrated that lower tool electrode temperature brings the higher material removal rate, lower relative loss of tool electrode and smaller workpiece surface roughness [8,9]. However, these methods still have some disadvantages on cooling effect of tool electrode and the processing effect of tool electrode cooling methods cannot be developed fully.…”

“…The common electrosparking precision of ±0.005mm cannot meet the requirements of high-precision customers that electrosparking size of high-density semiconductor encapsulation mould workpiece is no higher than ±0.002mm and the clearance angle processing is no larger than R0.02mm. Major measures to increase electrosparking precision include using high-precision electrosparking equipment, optimizing electrosparking processing parameters [3,4] and research and development of new electrosparking technology [5][6][7][8][9].…”

“…Results demonstrate that the ultrasound-assisted low-temperature electrosparking high-speed steel could make tool electrode maintain a relatively high shape precision and could lower electrode loss rate and surface roughness significantly. Abdulkareem S et al [8,9] studied influences of liquid nitrogen forced cooling electrode on electrosparking processing of Titanium alloy TC4. In the electrosparking test, they compared electrode loss when there's or no liquid nitrogen cooling effect.…”

Surface modification of Ti-6Al-4 V by gas–liquid mixed EDM

“…That maybe due to the discharge energy enhances with the peak current and pulse duration increase, which leads to more materials melting. However, the proportion of molten material that can be ushed away by the dielectric is constant [23]. Thus, more molten materials re-solidi ed on the workpiece surface compared with that of small parameters.…”

Discharge characteristics of cool electrode in EDM based on monopulse discharge

“…Abdulkareem et al demonstrated that machining Ti-6Al-4V with cool electrode has low EW but high processing efficiency and that the surface of workpieces subjected to EDM by cool electrode has many micro-cracks and a thick recast layer [11][12][13]. However, the discharge characteristics of cool electrode have yet to be studied.…”