Copper vapor laser micromachining of 304 stainless steel

A copper vapor laser (CVL) of 511/578 nm wavelength, 25 ns pulse width, and 10 kHz repetition rate combined with a computer controlled galvo head was used for laser micromachining of 304 stainless steel. The objective of this study was to develop the CVL micromachining process and its optimization. We observed a significant improvement in micromachining quality with a spatially filtered beam. Micromachining experiments were carried out on stainless steel strip samples of 75, 153, and 356 μm thickness. We studied the ablation rate using a single pulse and monitored the heat affected zone (HAZ) as a function of the applied laser power density. The ablated volume and HAZ are directly proportional to the applied laser power density for low to medium laser powers (up to 2×1013 W/m2). The ranges of HAZ diameter and ablated volume were 15.3–28.7 μm and 112.8–537.6 μm3, respectively, for the applied power density in the range of 1.0–63.7×1013 W/m2. The roughness created by ablation process was studied at various pulse overlaps at laser power density of 87.8×1013 W/m2. Ablation depth and surface roughness were found to be inversely proportional to the center-to-center pulse overlap and directly proportional to the power density.