Femtosecond Laser Micro-drilling on Stainless Steel 316 L at Sub 90 μm Hole Diameter

Micro-hole perforation on stainless steel is essential for various industrial applications. However, achieving precise hole geometry, high aspect ratio, and excellent surface quality remains challenging with conventional drilling methods. In this study, we employed a single circular path trepanning technique using a femtosecond laser to drill micro-holes in 316L stainless steel with diameters less than 90 µm. Process parameters, including pulse energy, repetition rate, scan speed, and number of scans, were systematically varied. Resulting hole morphology and cross-sectional profiles were characterized using a confocal microscope and a scanning electron microscope. Our findings demonstrated that optimized femtosecond laser drilling could minimize recast layers, sputter deposition, and heat-affected zones, thereby achieving high-quality micro-holes suitable for demanding industrial applications.