An overview of electric discharge machining of ceramics and ceramic based composites

To overcome the technological limitations imposed by the metals, the industrial demand of advanced ceramic materials is continuously on the rise. This demand has called upon the researchers in the manufacturing domain to strive hard to evolve processes that can shape these hard and brittle materials, as near net shape of ceramics is very difficult to achieve with conventional sintering processes. Even grinding processes, with which the ceramics are shaped extensively, are cost ineffective and labor intensive; particularly in case of advanced ceramics. Several processes exist to shape these hard-to-cut materials but electric discharge machining (EDM) can prove to be very effective and advantageous, when it comes to machining complex three-dimensional shapes. This paper unfolds various research trends that employ EDM to machine insulating ceramic materials. The paper presents a classification of the ceramic materials and a comprehensive overview of EDM processes, along with its variants, including the hybrid ones, to machine various ceramic materials like ZrO2, Al2O3, Si3N4, SiC and their composites. Significant benchmarks for the machining of insulating ceramics have been identified and presented. The primary objective of this paper is to present a broader range of work that has been done towards machining of advanced ceramics. This overview includes not only the experimental work but also the finite element and numerical simulation models established to study the machining of insulating ceramics via spark discharges. The challenges associated with the machining of insulating materials with EDM process are discussed and these challenges are contrasted with the capabilities of the process to machine their composites. In addition to this, the areas, which demand significant research attention, have been identified and prospects of future course of the research are presented.