Potential of structuring and polishing with fiber laser on homogeneous metals

Abstract

Conventional processes to polish metallic surfaces are usually manual or semiautomatic processes and offer very good results. However, these solutions are limited by the part geometry which can have angles or edges to preserve. Moreover, these solutions are time consuming for the operator and consumable parts have to be replaced frequently due to erosion. Lasers, on the other hand, offer a good alternative to polish and smooth metal surfaces, preserving the edges, and solving the accessibility problems. Fiber lasers are perfectly adapted to industrial applications because they are low cost, with high efficiency, high reliability, and can easily melt metals. In this paper, we report on the latest developments in structuring and polishing metals by surface remelting with common fiber lasers. We focus our work on polishing low and high surface roughness. Laser treatment of high roughness surfaces can considerably reduce processing time compared to conventional processes and offers prepolishing approach from 100 to 200 s/cm2. High reflective parts can be made from lower surface roughness to create bright appearance or medical instruments (from 20 to 90 s/cm2). In terms of results, we mostly concentrate our process optimization efforts on the solidification defaults, the structure modifications and reduction of Heat Affected Zone. Thus, laser polishing can be used for industrial solutions in polishing molds with applications in health care, watch industry, aeronautics, and many more. Commonly such patterns are created by laser ablation but this process uses more expensive lasers, with lower efficiency and reliability, and with longer processing time. Moreover, metal becomes matt finished. With high power laser, depending on the laser power and scanning strategy on the metal, the melting pool can be moved to create complex patterns. Experiments have shown that we can obtain a pattern with around 200 μm height at 40 s/cm2. Thus, creating patterns can be up to 30 times faster than for laser ablation processes. The created surface is, in this case, smooth with polished surface finish.