Self-rounding fabrication of micro-cylindrical electrode arrays and comparative EDM performance in single-crystal and polycrystalline nickel-based superalloys

Nickel-based superalloys are widely used in aerospace and energy systems, and their surfaces often feature high-density micro-hole arrays for cooling or fluidic functions. Electrical discharge machining (EDM) is a widely adopted process for micro-hole fabrication. However, as nickel-based superalloys evolve from polycrystalline to single-crystal structures, the similarities and differences in their EDM behavior remain unclear. Arrayed cylindrical electrode EDM of micro-hole arrays can significantly improve machining efficiency and ensure hole positional accuracy. This study proposes a simple, low-cost, and scalable method to fabricate highly uniform cylindrical micro-electrode arrays by controlling the wear of micro-prism electrodes. Using this electrode array, comparative EDM experiments were conducted on single-crystal and polycrystalline nickel-based superalloys, and the resulting micro-holes were comprehensively characterized in terms of dimensional accuracy, surface morphology, and subsurface altered layer structure. The results show that micro-holes in single-crystal nickel-based superalloys have smaller diameters, higher roundness, lower surface roughness, and thinner recast layers. Particularly notable is the significant deformation of γ phase and γ′ phase in the heat-affected zone of the single-crystalline alloy. This study not only provides a practical approach for the low-cost fabrication of uniform micro-electrode arrays but also establishes a critical link between crystal structure and EDM-induced surface integrity, offering reference for the precision machining of single-crystal components.