Effect of assist gas on femtosecond laser micromachining of SiC ceramics: a combined numerical and experimental study

With the rapid progress in electronic information, aerospace, biomedical engineering, and micro-electromechanical systems, stringent requirements have been placed on device miniaturization and functional integration. As critical functional structural units, the machining quality and efficiency of microholes directly determine device performance and service reliability, representing a core bottleneck constraining technological advancement in related fields. Silicon carbide (SiC) ceramics, characterized by high hardness, high brittleness, and exceptional thermochemical stability, are recognized as typical difficult-to-machine materials. Femtosecond laser machining offers unique advantages for high-aspect-ratio microhole fabrication in hard-brittle ceramics; however, the assist gas configuration significantly influences laser energy utilization, machining efficiency and quality. This study systematically investigates the flow field characteristics of coaxial, off-axis, and hybrid configurations (combined off-axis and coaxial configuration) through computational fluid dynamics simulations and experimental validation. The results demonstrate that coaxial assist gas fails to establish directional flow within blind microholes, resulting in ineffective debris evacuation. In contrast, the hybrid configuration exhibits significant synergistic effects, establishing stable directional high-velocity flow fields within microholes under optimized parameters. Experimental results confirm that the hybrid configuration significantly improves laser machining efficiency and surface quality. These findings provide theoretical foundations and technical guidance for high-efficiency, high-precision fabrication of high-aspect-ratio microholes using femtosecond lasers.