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Micro-EDM performance of Inconel 718 superalloy with and without ultrasonic vibration

Inconel 718 superalloy is an extremely difficult-to-machine aerospace material due to its work hardening nature and poor thermal conductivity. Drilling of cooling holes in this material is much difficult by conventional drilling processes because it has high chemical affinity with cutting tool materials, high welding action of chips at rake face, high strength at high temperature and work hardening nature. In consideration of all these problems, a self-developed setup of drilling ultrasonic assisted micro-EDM (drilling-UA-micro-EDM) has been used to create microholes in this material. A comparative study of machining characteristics of Inconel 718 in terms of material removal rate (MRR), tool wear rate (TWR), hole taper (Ta), and radial overcut (ROC) has been investigated due to drilling-micro-EDM without and with the ultrasonic vibration (UV). Comparative results show that the application of UV in drilling-micro-EDM increases MRR and decreases TWR, Ta and ROC, and gives microholes of good quality and accuracy.