Surface Roughness Formation in Powder Bed Fusion of Copper Using Gaussian and Ring-Shaped Laser Beam Profiles

Both Gaussian laser beam profiles and ring-shaped laser beam profiles demonstrate the capability to produce specimens with a part density of more than 99.5% and an electrical conductivity above 99% compared to the International Annealed Copper Standard (IACS) in powder bed fusion of copper using a laser beam (PBF-LB/M/Cu). However, the influence of the beam profile on the surface roughness and surface characteristic has not yet been investigated in detail. In order to close this gap, inclined cube geometries are manufactured with varying laser power and scan speed using a Gaussian and ring-shaped beam profiles. The results reveal that the beam profile achieving the lowest surface roughness Sa in the investigated parameter range depends on the surface orientation. For the down-skin surfaces, the use of ring-shaped beam profiles reduces the surface roughness Sa by up to 29.9% compared to the Gaussian beam profile, whereas the surface roughness Sa for the up-skin and side surface is more than doubled. This is related to differences in surface roughness formation of the Gaussian and ring-shaped beam profiles, which are discussed in detail. For all investigated beam profiles, changes in the height of the peaks, depth of the valleys and the number of attached particles on the surface are observed with varying laser power and scan speed. Furthermore, a trend between the surface roughness Sa of the inclined cube geometry and the aspect ratio R of the weld geometry is found, indicating that the welding regime influences the surface roughness.