An experimental study on drilling through and blind holes on inconel 718 by electrical discharge machining

Electrical Discharge Machining (EDM) process has been used for making holes on difficult-to-cut materials in aerospace industry. There are several process parameters affecting performance of EDM operations. Workpiece material, electrode properties (i.e. material and shape of electrode) and type of holes to be drilled (i.e. through or blind) also influence the state of EDM process. Therefore, appropriate machining conditions should be provided for drilling holes in an accurate and effective way. In this study, an experimental investigation was conducted on making through and blind holes on nickel-based super alloy Inconel 718 (namely IN718). Several holes (Ø2 mm) were drilled at two levels of process parameters (low and high values of current, pulse-on and pulse-off time, capacitance) using two types of brass electrodes (having single and multi-channels). Process performance was analyzed based on Material Removal Rate (MRR) and Electrode Wear Rate (EWR). Diameter and depth of drilled holes were measured in order to evaluate their dimensional accuracy. Surface Roughness (SR) measurements as well as Energy Dispersive X-ray (EDX) analyses were conducted to examine the characteristics of hole surfaces. The results revealed that use of multi-channel electrode and high-level parameters are the most appropriate conditions for drilling through and blind holes in aspects of lower drilling time, better dimensional accuracy, and improved surface quality.