Experimental investigation into the micro-EDM characteristics of conductive SiC

SiC is an advanced ceramic which finds wide range of industrial applications. Cutting of SiC is difficult using conventional machining methods due to its low fracture toughness. In the past few years, researchers have claimed successful machining of SiC using EDM process. Furthermore, increasing trend for miniaturization in MEMS and semiconductor industry has necessitated the development of micro-machining methods for advanced ceramics. Therefore, this research was focused on micro-EDM of SiC. In this work, the effect of voltage, capacitance and threshold on surface roughness, MRR, TWR, radial overcut (ROC) and residual stresses was studied through experiments. Signal to noise ratio analysis was used to determine the optimum machining parameters in conjunction with ANOVA. The surface condition of the machined surface was studied using SEM and EDX. The experimental observations revealed that during µEDM operation, all the process parameters (Voltage, Capacitance and Threshold) affect the Surface Roughness, MRR, TWR and ROC significantly. The process input parameters are directly related to micro discharge energy which affects the process performance. Experimental results and optimization attempts show that in micro-EDM of SiC, optimum machining conditions for good surface finish are 150 V, 0.1 µF and 60% threshold. For high MRR, the optimum conditions are 150 V, 0.4 µF and 80% threshold. Optimum parameters for low TWR are 110 V, 0.4 µF and 40% threshold and those for low ROC are 110 V, 0.4 µF and 60% threshold. Surface characterization revealed the presence of debris, resolidified material and craters on the µEDMed surface that were responsible for high surface roughness. XRD analysis revealed the presence of compressive residual stresses of the order of 1200 N/mm2 on the µEDM surface and their magnitude varied slightly with the input parameters. EDX analysis revealed the bidirectional material migration phenomenon in µEDM of SiC.