Effect of surfaces and surface-modification processing on properties of PBF-LB/M parts

Abstract Metal additive manufacturing, and in particular laser-based powder bed fusion (PBF-LB/M), enables the fabrication of components with complex geometries and high functional integration, but typically results in relatively rough as-built surfaces that can adversely affect both mechanical and functional performance. Surface quality is especially critical for particle accelerator components, such as radio-frequency circuits, waveguides, and antennas, where skin effects become increasingly relevant with uncontrolled surface roughness. This paper provides an overview of the origin of surface features in PBF-LB/M parts, with specific attention to pure copper components, highlighting the effects of melt pool dynamics, defect generation and build orientation on surface morphology and roughness. The processing of high-purity copper using both infrared and green laser sources is then discussed, showing that optimized parameters allow the production of nearly fully dense parts with electrical and thermal properties comparable to wrought copper. The influence of build orientation on surface roughness is quantitatively analysed. Furthermore, mass finishing treatments are investigated as an effective post-processing strategy to significantly reduce surface roughness of PBF-LB/M copper components. A two-step vibro-finishing process is shown to decrease the average roughness from the as-built condition to sub-micrometric values, effectively removing surface defects associated with the additive manufacturing process. These results demonstrate the key role of surface engineering in enabling high-performance PBF-LB/M copper components for demanding applications.