Stream Finishing of Additively Manufactured AlSi10Mg PBF-LB Parts: Influence on Surface Quality and Fatigue Behaviour

Due to the large design freedom of additive manufacturing (AM), components manufactured by laser powder bed fusion (PBF-LB) possess a high lightweight potential, which increases the importance of PBF-LB for applications in the automotive, aviation and aerospace industries. The typically high surface roughness of PBF-LB parts leads to a significant reduction in fatigue strength. Therefore, a finishing process for improving the surface roughness of complex PBF-LB parts is required. Stream finishing represents such a process. In a first step, surface roughness evolution and abrasion rates were measured for specimens manufactured with PBF-LB at different stages of the finishing process. In a second step, fatigue specimens were manufactured, machined both by turning and stream finishing, and tested by rotating bending fatigue tests. To evaluate crack initiation and propagation, the fracture surfaces were examined by scanning electron microscopy. The microstructure and microhardness near the surface were investigated to assess the influence of the surface layer on the fatigue behaviour. Stream finishing proved to be a suitable finishing process, as the specimens exhibited very low surface roughness and improved fatigue behaviour compared to turned specimens, especially for lower stresses.