Reducing Feature Size in Laser Implantation Texturing ^†

Embossing rolls are used in a variety of sectors to transfer surface textures to a product. Textures on the rolls are typically achieved by material-removal techniques, resulting in craters in the surface of the roll. The wear resistance of the surfaces is improved by additional coating technologies. A novel process offering improved surface design freedom and which negates the need for post-coating techniques is the embedding of micro-meter-sized ceramic particles in the surface of the roll. This can be achieved through micro-additive processing. This work presents and discusses experimental results of surface texturing through locally derived laser-induced melt pools in which ceramic particles are dissolved. This process is termed laser implantation, or laser dispersing. Using this technology, dome-shaped surface structures with significantly increased hardness compared to the bare steel can be achieved. Reported results in the literature focus on implantations with diameters ranging from 150 $\mathsf{\mu }$m to 400 $\mathsf{\mu }$m and heights ranging from 10 $\mathsf{\mu }$m to 30 $\mathsf{\mu }$m. However, features with smaller diameters and heights are desired for technology adoption to permit a wider range of surface roughness. This paper presents and discusses the experimental results of implantations with a diameter smaller than 150 µm, with heights between 1 $\mathsf{\mu }$m and 15 $\mathsf{\mu }$m. For that purpose, a Nd:YAG laser source (focal diameter 70 $\mathsf{\mu }$m, pulse durations from 3 to 15 ms, pulse power from 20 to 50 W average) was used to induce a melt pool driving the particle embedding.