Experimental Investigation and Parameter Optimization of Micro-Hole Electrical Discharge Machining of ZrB2–SiC Ceramics

ZrB2–SiC ultra-high-temperature ceramics have important aerospace applications, but their high hardness and brittleness make conventional machining difficult. This study investigated micro-hole electrical discharge machining (micro-EDM) of ZrB2–SiC ceramics using a resistance–capacitance relaxation pulse generator. Single-factor experiments examined the effects of capacitance, voltage, and resistance on the material removal rate (MRR), relative electrode wear ratio, and taper angle. Scanning electron microscopy was used to characterize the machined surfaces. A three-factor, five-level orthogonal design was subsequently employed, and signal-to-noise ratio analysis, range analysis, and analysis of variance were used to quantify the effects and percentage contributions of the machining parameters. Entropy weighting was combined with grey relational analysis to identify a parameter combination that balanced machining efficiency, electrode wear, and hole taper. The selected combination was a capacitance of 10,000 pF, a voltage of 156 V, and a resistance of 500 Ω. Compared with the combination predicted from the factor-level means, this combination reduced the relative electrode wear ratio by 10.34% and the taper angle by 9.11%, with an 11.24% decrease in MRR. Because the orthogonal array was based on single-run experiments (n = 1), the S/N ratios and ANOVA p-values are used for factor ranking and descriptive contribution analysis rather than for formal significance testing. These results provide an experimental basis for selecting process parameters for micro-EDM of ZrB2–SiC ceramics.