Laser polishing of additive manufactured L-PBF copper parts with visible laser wavelength of 515 nm – Challenges due to high surface roughness

Abstract

Copper components produced by Laser Powder Bed Fusion (L-PBF) have a high surface roughness of up to Ra = 21.6 µm. The surface has a structure depth of up to 300 µm, as well as porosity. In order to smooth this surface, laser polishing of copper is being investigated. A challenge here is the low absorption of the near-infrared laser beams as well as the high thermal conductivity of the copper material. To increase the absorbed laser radiation, a 1 kW laser source in the visible green wavelength range is used instead of a near-infrared laser source. In the first-time investigations of laser polishing of copper, the laser beam intensity, the line energy as well as the track overlap are varied. Microscope images, cross-sections and tactile roughness measurements are used for the analysis. A laser beam intensity of 4.95 kW/cm² is required to completely remelt the high surface structure depth without porosity. The surface roughness could be reduced by 85.2% from Ra = 21.6 µm to Ra = 3.2 µm.