Ultrashort pulse laser micro polishing of steel - Investigation of the melt pool depth

For the most demanding applications in mold and tool manufacturing, ultrashort pulsed laser structured surfaces sometimes do not meet the requirements for surface roughness. A subsequent polishing step in the same machine with the same beam source offers a time and cost effective solution. The novel approach of ultrashort pulse laser polishing with a pulse duration of t=10 ps is investigated experimentally and theoretically in the present study. It is shown that a low micro roughness is achieved with a melt pool depth between 1 and 3 µm in hot-working steel 1.2738, which allows a polishing process for surface structures with small and fine geometry features without influencing the structure itself.