Surface roughness and radiusing of Ti6Al4V selective laser melting-manufactured parts conditioned by barrel finishing

Selective laser melting is, at present, one of the fastest growing additive manufacturing technologies. It allows the manufacture of functional components characterized by high complex geometries with engineering-grade metals. Notwithstanding, it is employed in many industries such as aerospace, automotive, biomedical, and defense; a great limitation for its diffusion is the obtainable surface quality. This work aims to improve the surface of Ti6Al4V parts produced by this technology through barrel finishing. It is a mass finishing operation able to condition parts by means of a soft mechanical action provided by a granular flow. Since no part fixing is needed and a lot of materials with complex geometries can be processed, it is a good candidate for the conditioning of additive-manufactured parts. An experimental plan has been designed considering aspects such as the involved granular motions, the charge composition, and the parts built orientation. The barrel finishing process parameters have been experimented by the development of the bed behavior diagrams in order to set a parameters window adequate for the finishing operation. The selective laser melting surface morphology and its evolution during the barrel finishing processing have been investigated via profilometric, macroscopic, and microscopic analysis: this allowed the evaluation of the conditioning action in terms of obtainable roughness and radiusing. Results showed a marked decreasing of the average roughness and an increasing of the edge radius. Finally, the modification in terms of dimensional accuracy and the mechanical properties of the finished parts have been evaluated.