Femtosecond laser texturing of DLC-based coatings by DLW method with sub-micrometer precision

Abstract

Laser texturing of surfaces may provide specific functionality, such as altering hydrophobicity, changing optical properties, or reducing friction and wear. For the latter, surfaces of parts are often coated with protective and/or solid lubricant coating, and texturing may further improve the tribological properties in both dry or lubricated sliding. New laser technologies, such as the direct laser writing (DLW) method using a femtosecond laser, allow the production of extremely precise textures directly into the coating. Here, we describe a method of preparing ultra-precise textures into diamond-like carbon (DLC) coatings on a large area. The textured topography was assessed by 3D laser scanning microscope, which confirmed the repeatability of fs laser processing. Raman spectroscopy mapping, SEM, and XPS were combined to investigate the effect of laser processing on DLC coating in terms of oxidation or structural changes. Traditional process (i.e., coating textured surface) often results in coating adhesion/cohesion failure due to deposition of sharp edges produced by texturing, whereas our approach eliminates this issue. Even complex textures inside the coating are fabricated with a fast speed of 10 s per mm2 and a high precision in texture depth (tens of nanometers), unlocking many application fields in tribology or microfluidics.