Surface and Subsurface Study on EDG and EDM Processing of Advanced Ceramic Composite Material

Abstract

The advanced ceramic composites are made electrically conductive by doping with the conductive phase elements like TiN, TiC, TiB2 and TiCN. The doping of the naturally occurring nonconductive ceramic composite makes it suitable to be machined by unconventional machining processes where conductivity of the material plays prominent role. Though, the ceramic materials are fragile in nature, these are custom-tailored for the engineering applications. The machining of the ceramic material by conventional processes is quite difficult and leads to failure of the material under high cutting forces due to its fragile nature. In most of the cases deformities like surface and subsurface cracks, inclusion of pits and voids, deteriorates the functionality of the ceramic material. In our work, we have studied the surface and subsurface characteristics, while processing the material by electric discharge machining (EDM) and electric discharge grinding (EDG) processes. A setup has been designed, developed and mounted as an attachment on die-sinking EDM machining facility to carry out the EDG experiments. The conductive alumina ceramic has been chosen as workpiece material for processing. The surface characteristics has been observed by scanning electron microscopy (SEM) at the resolution of 1000X for EDG processed work pieces, and at 500X for EDM. In EDM machining, the surface contains the recast layer whereas in EDG, the recast layer is either removed or swept uniformly along the surface giving good glossy surface finish. It has been found that the components produced by EDM process contain prominent surface and subsurface cracks whereas such deformities are not visible in case of EDG processing. The best surface finish achieved is of the order of 0.04μm when processed by EDG.