Surface functionalization of metal surfaces by large-area USP laser texturing

Ultra-short pulse laser texturing is a well-known one-step technique used to transform the surface properties of different materials in order to functionalize them for specific applications. According to the laser and process parameters, several features can be achieved, as surface coloring, blackening and super-hydrophobicity. In this work, an upscaling approach is considered for generation of surface structures and thermal effects, connected to the use of high-average power lasers are considered in relation to the influence of the laser pulse duration and repetition rate on the final surface morphology. Mirror-polished 316L steel samples were textured by an UPS laser source with pulse duration of about 450fs and running at 1030nm, at two different repetition rates, 250kHz and 1000kHz. Results show that two main sources of thermal effects are identified: (i) heat accumulation due to the use of high repetition rates and (ii) thermal diffusion effects linked to the intrinsic nature of the material. When employing high repetition rates, a lower cumulative energy is necessary to highlight the influence of the pulse duration on the surface morphology. Finally, the influence of pulse duration and wavelength on the wetting properties of the material surface are also investigated.