Machining Performance Characteristics of Inconel 718 Superalloy Due to Hole-Sinking Ultrasonic Assisted Micro-EDM

Abstract

Inconel 718 superalloy is widely used in aerospace industries for fabrication of the various components for aircraft engine because of its high strength at elevated temperature. It is an extremely difficult-to-machine material due to its work hardening nature and poor thermal conductivity. Creating micro-holes of high precision in this material is beyond the capability of conventional twist drill due to its low thermal conductivity. Micro-electrical discharge machining (micro-EDM) is a well-established process for the machining of any electrically conductive hard and brittle material, but due to very small feature size and narrow discharge gap, removal of debris becomes difficult, causes arcing and short-circuiting. In order to solve this problem, authors indigenously developed an innovative ultrasonic-assisted micro-EDM setup for workpiece vibration. The machining performance characteristics of Inconel 718 superalloy was studied using the developed setup in sinking configuration in terms of material removal rate (MRR), tool wear rate (TWR) and hole taper ([Formula: see text]) considering the effect of ultrasonic power, gap current, pulse on time and pulse off time. It was observed that higher ultrasonic power was more suitable for higher MRR, lower TWR and [Formula: see text]. It was also found from the results that 3 A gap current at 6[Formula: see text][Formula: see text]s pulse on time was appropriate for better MRR and 12[Formula: see text][Formula: see text]s pulse on time was more appropriate for low TWR and [Formula: see text]. The scanning electron microscope (SEM) analysis of created micro-holes was also performed with and without ultrasonic vibration to ensure the quality as well as accuracy.

The effect of ultrasonic amplitude on the performance of ultrasonic vibration-assisted EDM micro-hole machining

“…Reference source not found.) is as follows: (6) but L1 is usually larger than Au, and L can be considered equal to L1.…”

“…Hence, EDM is more suitable for machining micro-holes because no macroscopic mechanical force appears during the process [5] . Nevertheless, the EDM of micro-holes still faces the problems of accumulating debris at the micro-hole bottom, which will produce abnormal discharge like arcing and short circuits, leading to poor shape accuracy and low material removal rate (MRR) [6] .…”

Multi-objective parameter optimization of ultrasonic vibration–assisted micro-EDM of Ti-6Al-4V alloys

“…In order to improve the abnormal discharge state in micro-hole machining and improve the machining efficiency of μ-EDM, since the 1930s, scholars have conducted much research on improving the MRR, reducing the TWR, and optimizing the surface quality (SQ) of the processing workpiece (Kunieda et al, 2005). Researchers combine ultrasonic vibration with μ-EDM and apply high-frequency ultrasonic vibration to workpiece materials, tool electrodes, or work liquids to assist μ-EDM (Singh et al, 2017(Singh et al, , 2018Sundaram et al, 2008). Applying ultrasonic vibration can effectively promote debris discharge in the micro-hole and reduce the phenomenon of abnormal discharge.…”