Effect of Finishing Technology on 316L Stainless Steel Internal Surfaces Produced by Additive Manufacturing

Additive manufacturing technologies are continuously expanding their range of applications, with new use cases emerging across an increasingly broad spectrum of industries. From mechanical engineering to the medical sector, virtually all additive manufacturing applications require subsequent processing steps, whether in the form of material removal operations or surface finishing treatments. The present work aims to investigate the effects of various surface finishing technologies applied to different metal additive manufacturing processes, with particular emphasis on internal surfaces and on the influence of component geometry. A test artifact designed to satisfy multiple geometric criteria was manufactured using four manufacturing conditions derived from three metal additive manufacturing technologies (PBF-LB/M, MBJ, and MSD), which were subsequently combined with five distinct post-processing treatments. Finally, the effects associated with the different investigated factors are discussed, including the porosity of the as-built component, the initial surface roughness, the type of post-processing treatment (abrasive, chemical, electrochemical, or hybrid), and the variability induced by surface geometry. Surface roughness reductions exceeding 50% were achieved for most of the investigated process combinations. CP and AFM consistently produced the lowest roughness values, frequently achieving Ra values below 2 μm. While AFM exhibited a stronger sensitivity to channel diameter and local geometry, CP was not influenced by these variables as much. The results demonstrate that the effectiveness of internal surface finishing remains strongly dependent on the initial as-built roughness generated by the selected additive manufacturing technology.