2, Department of Energy's National Security Campus, Managed by Honeywell, Kansas City, Missouri, United States
Reducing the surface roughness of an additive manufacturing (AM) component is one of the most critical factors in determining the suitability of an AM component. The typical as produced surface roughness of an AM component range from 100-500 micron inch. However, for most of the engineering application surface roughness must come down below 10 µ inch. Reducing surface roughness is exponentially more challenging for the internal surfaces of a component. This paper reports our research in the area of postprocessing of the interior surfaces of the AM component. We have applied electropolishing and chemical polishing methods to reduce the surface roughness of the internal surface. We found that chemical polishing route was very effective in simultaneously reducing the internal and external surface roughness of the steel AM components from ~300 µ inch to ~20 µ inch range. Chemical polishing is found suitable for any complicated AM shape and geometry. Our electropolishing methodology was very effective in reducing the surface roughness of the internal or external surface individually but not simultaneously. However, electropolishing produced the relatively better performance on the outer surfaces with the optimized process parameters. The surface roughness of the 316 steel AM components reduced from 300 µinch.to 3 µinch. However, electropolishing of the internal surfaces of the cubical or spherical cavity was not uniform and was very much dependent on the counter electrode geometry, electrolyte flow rate, and bath temperature. In this paper, we will summarize our research efforts to tackle the critical issue of reducing the surface roughness of the complex AM components.