Effect of electrode material in micro-electrical discharge machining of micro-holes drilled in shape memory alloys

Abstract

Machining of advanced engineering materials is a major problem faced by the industry. Electrical discharge machining (EDM) provides a solution to this problem, and it is utilized for machining of such electrically conductive materials. Micro-EDM (µEDM) technology is used to drill micro-holes in various components in the aerospace industry and automotive industry. Such holes need to have good surface finish and good dimensional accuracy. It is difficult to maintain a high accuracy and good surface finish at such a minute level. Therefore, this work tries to solve this issue by conducting an experimental study in which micro-holes are drilled in the Ni-Ti shape memory alloy (SMA) and stainless steel (SS) using µEDM. The effect of the electrode material on micro-holes is investigated. Surface characteristics and dimensional accuracy of the machined micro-holes are evaluated based on micrographs obtained by scanning electron microscopy (SEM). The results reveal that the material removal rate (MRR), surface finish, and dimensional accuracy are significantly affected by the machining parameters (i.e., discharge energy (pulse voltage and capacitance) in R–C circuit during machining), tool electrode material, and type of hole to be drilled (through hole or blind hole). In addition, fine surface finish is also dependent on the electrical and thermal properties of the electrode material.