Surface and near-surface defect reduction by ISF process: improving mechanical performance of AM components by surface finishing.

Additive manufactured (AM) components are making their way into the aerospace industry at an accelerated rate. AM is a viable option to produce complex, yet lighter components, and in many cases with shorter lead time. Nevertheless, AM-produced components have an extremely rough surface. They are often packed with multiple layers of partially melted/sintered powder, and have significant surface and near-surface defects. Given that the geometry of AM-produced parts is often quite complex, traditional surface finishing is not a viable option. Consequently, there is a latent need for surface finishing techniques capable of improving the surface texture of the AM-produced components, and by the same token improving their mechanical properties. The Isotropic superfinishing (ISF^®) process, a chemically accelerated vibratory finishing (CAVF) is one of the most successful surface finishing processes reported in the literature to date. The ISF^® process has demonstrated the ability to improve the surface texture of complex components. It can also remove the partially melted/sintered metal particles from the surface, and improve bending fatigue and tensile strength by targeting the surface and near surface defects. This paper will discuss how the surface chemical activation by the ISF^® process is capable of producing surface-finished components that meet the requirements of the aerospace industry. The different types of surface textures that characterize AM‑built components will be described, as well as the improved mechanical properties obtained via the ISF^® process. Moreover, a detailed discussion regarding the different AM alloys that have been processed by ISF^® (EBM and SLM Ti-6Al-4V, IN-625, IN-718, PH15-5, and 316L components) along with their complete surface texture profile will be provided. Tensile strength and bending fatigue testing of AM-produced Ti-6Al-4V and IN-625 components processed by ISF^® will also be presented to demonstrate the improvements in mechanical performance.