Investigation of scanning strategies on performance of nanosecond and picosecond laser volume ablation of bronze

Understanding of laser volume ablation performance in different scanning strategies is indispensable for practical applications. This study investigates the influence of different laser scanning parameters on the performance of volume ablation of bronze material. The results reveal significant differences between the selected pulse durations of 16 ns (ns) and 12 picoseconds (ps), despite both using an identical maximum average power of 40 W. In both cases, increasing the scanning area resulted in a proportional increase in ablation depth. Compared to the ns-laser, the ps-laser exhibited significantly lower ablation depths, approximately 35 % to 40 % less, with consistent performance across different scanning directions. Surface topography analysis showed that scanning direction played a crucial role in determining the final surface quality, with a nearly 50 % improvement observed with the mixed scanning strategy. With the ps-laser, expanding the scanning area led to reduced surface roughness, primarily due to pure ablation and minimal surface re-melting. Further strategies, such as interlace and halftone were also explored. Adjusting the line delay time was also considered, with longer delays potentially resulting in deeper ablation and slightly improved surface roughness. The study also investigated the pitting phenomenon, which was found to be intensified around contour edges. Notably, pitting was more pronounced in ns ablation during the initial scanning layers, while in ps ablation, pitting distribution intensified with an increase in scanning layers and ablation depth.