Investigation on the Laser Surface Treatment of Steel and Aluminum with a Single-Mode Pulsed Fiber Laser Source

The effects of modifying the microstructure of a surface on its macroscopic properties have been studied intensively in the last decade, a well-known example being the generation of superhydrophobic surfaces with laser beams. For such kind of surface treatment, where the surface roughness (R_a value) is typically either increased or decreased, pulsed fiber lasers are an excellent tool. By focusing energy into a small spot on the surface, local intensity greater than the ablation threshold of the material can be reached and a portion of it is removed from the surface. Controlling the size and spacing of each of these holes or trenches allows to precisely modify the roughness (R_a value). For this study, we used a single-mode pulsed fiber laser with 100 ns pulse duration and up to 1 mJ pulse energy combined with a high-speed galvanometer scanner. Several parameters of the process were optimized in order to determine the induced roughness rate (cm²/s for different R_a values) achievable at full power on steel and aluminum.