Micro hole fabrication in TiN-Al2O3 ceramic composite by SiC powder assisted micro- EDM

Abstract

Considering the importance of ceramics in many microdevice applications, a modified micro-electrodischarge process in which the addition of silicon carbide powders in the dielectric was used to fabricate high aspect ratio microholes in dense and hard TiN-Al2O3 ceramic composite has been described in the present paper. TiN-Al2O3 ceramics has been prepared by reactive hot pressing technique. Response Surface Methodology (RSM) has been employed to design and optimize the experimental input parameters like voltage, capacitance, and tool rotation speed and for evaluating the responses in terms of Material Removal Rate (MRR), Electrode Wear Rate (EWR), Radial Overcut (ROC) and Taper Angle (TA). SiC powder addition has shown the improvement in MRR by 6.5 times, reduction of TA by 2 times and reduction in ROC by 1.5 times. However, EWR has increased by 1.8 times. Improvement in the machining performance has been analysed with respect to the early breakdown of the dielectric fluid by the addition of SiC powder and the enlargement of the discharge gap. Topographies of the machined surfaces analysed from the Scanning Electron Micrographs (SEM) show smoothening of the surface by SiC powder addition and reduction of tool rotation speed. Chemical compositions of the machined surfaces determined by energy dispersive spectral analysis (EDS) showed the formation of amorphous Ti-Al-O-N phase by the discharge. Thermal micro-cracking of the amorphous solidified melt, spalling, micro-bubble formation and accumulation of spherical electrode debris have been observed during the machining of TiN-Al2O3 ceramic-composite.