Impact of the Deionized Water on Making High Aspect Ratio Holes in the Inconel 718 Alloy with the Use of Electrical Discharge Drilling

Abstract

Nickel-based superalloys are being increasingly applied to manufacture components in the aviation industry. The materials are classified as difficult-to-machine using conventional methods. Nowadays, manufacturing techniques are needed to drill high aspect ratio holes of above 20:1 (depth-to-diameter ratio) in these materials. One of the most effective methods of making high-aspect-ratio holes is electrical discharge drilling (EDD). While drilling high aspect ratio holes, a crucial issue is the flushing of the gap area and the evacuation of the erosion products. The use of deionized water as the dielectric fluid in the EDD offers a considerable potential. This paper includes an analysis of the influence of the machining parameters (pulse time, current amplitude and discharge voltage) on the process performance (drilling speed, linear tool wear, taper angle, hole’s aspect ratio, side gap thickness), during the EDD with the use of deionized water in the Inconel 718 alloy. The obtained through holes were subjected to the extended analysis. The impact of the initial working fluid temperature and pressure on the conditions of the flow through the electrode channel was also subjected to the analysis. The deionized water properties were changed by applying an initial temperature. Based on the results of an analysis of the previous research, the EDD of the through holes was performed for a pre-set initial temperature (~313.15 °K) and initial pressure of the working fluid (8 MPa) and selected process parameters. An analysis of the results indicates increasing of hole’s aspect ratio by about 15% (above 30), decreasing the side gap thickness by about 40% and enhanced surface integrity.

Investigation of the Machinability of the Inconel 718 Superalloy during the Electrical Discharge Drilling Process

“…This can be the result of various temperatures of deionized water, which is related to its electrical conductivity. In [31], the analysis of the results shows that the deionized water temperature affects the condition at the machining area, and the change in its electrical conductivity. The application of a higher initial working fluid temperature (about 313.15 • K) improves the dimensional shape accuracy of drilled holes (the side gap thickness decreases by about 40%).…”

“…In the case of the EDM drilling of high-aspect ratio holes (above 20:1) with a diameter of less than 1 mm, effective gap flushing is a challenge [31]-even during the application of a high volumetric flow rate (25 L/h) [32]. To prevent secondary discharges between debris and the hole sidewall, a satisfactory approach is to cover the sidewall of the tool electrode with a non-conductive coating.…”

Multi-Response Optimization of Electrical Discharge Drilling Process of SS304 for Energy Efficiency, Product Quality, and Productivity

“…Step 1: The EDD trials using full experimental design are conducted to collect the necessary data [32,33].…”

Achieving the Minimum Roughness of Laser Milled Micro-Impressions on Ti 6Al 4V, Inconel 718, and Duralumin

“…Nickel alloys, especially Inconel 718, is also considered as difficult-to-cut material owing to have lower thermal conductivity, high work hardness, and high toughness. Machno et al [ 11 ] reported that the presence of abrasive carbide particles in nickel alloys creates much more difficulty during conventional machining processes. Aluminum alloys are relatively less hard as compared to titanium and nickel alloys.…”