Reducing Feature Size in Laser Implantation Texturing

Abstract

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 μm to 400 μm and heights ranging from 10 μm to 30 μm. 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 μm and 15 μm. For that purpose, a Nd:YAG laser source (focal diameter 70 μm, 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.