Surface characterization and statistical texture analysis of fabricated large-area micro-textured surface: effects of tool materials and EDM parameters

The present study explores the impact of different tool electrode materials—mild steel (MS), copper (Cu), and tungsten copper (WCu)—on the electrical discharge machining (EDM) performance of H13 steel for functional micro-texturing, focusing on process optimization and comprehensive surface characterization. Surface properties and crater distribution vary with electrode material. WCu produces the smoothest surfaces and most uniform craters, followed by Cu, while MS results in rougher surfaces and irregular crater patterns. The tungsten-copper tool demonstrated the best performance for large-area micro-texturing, with the optimal parameter combination of 2 A peak current, 100 µs pulse on-time, and 40 V gap voltage, and the form tool featured square micro-pillars pattern. The EDM-textured surfaces exhibit micro-cracks, pockmarks, voids, and resolidified materials of the workpiece and tool. The adverse morphological change (regions of more significant recast deposition) of the patterned surfaces leads to a rougher surface profile that results in a higher variance in the texture pattern, as revealed by statistical texture analysis. The rougher surface profile, combined with material deposition from the tool, enhances the hydrophobicity of the textured surface—evident from the increase in water contact angle from 80.24° to 110.70° and glycerol contact angle from 66.53° to 77.60°. This is accompanied by a significant rise in the dispersive component of surface energy, promoting better interaction with non-polar or weakly polar fluids while reducing interaction or Work of adhesion with polar fluids like water, significantly improving the corrosion resistance of the patterned die surfaces.