Reducing surface roughness by chemical polishing of additively manufactured 3D printed 316 stainless steel components

Abstract

As-produced laser-sintered metal additively manufactured components possess a high roughness and unsuitable surface texture that may lead to several forms of crack generation under static and dynamic loading. This problem is even more severe for additively manufactured (AM) components with intricate geometries involving a large internal surface area. Here, we report the application of the chemical polishing method to improve the surface finish of 316 steel components. After chemical polishing, the AM component surface became dull gray to bright lustrous and surface morphology improved remarkably. As a distinctive advantage, chemical polishing effectively reduces the roughness of the internal and external surfaces of the AM component. The Ra roughness parameter changed from ~ 5 to ~ 0.4 um for the outer surface. However, for the inner surface of the AM component, where abrasive blasting or shot pinning was unable to remove loose metal powder, the Ra surface roughness reduced from ~ 15 to ~ 0.4 um. Our SEM study showed that chemical polishing produced the surface texture covered with ~ 0.3-μm-wide sub-microscopic convex hull-shaped regions. During chemical polishing, material removal preferably occurred from the interior regions of the ubiquitous sub-microscopic regions. The roughness measurement conducted with SEM on a ~ 20-μm scan length chemical polished sample was Ra 0.37 μm. Roughness study in SEM was in close agreement with the roughness measurement performed with optical profilometer over several millimeter-long scan lengths resulting in a ~ 0.4-μm Ra. These studies suggested that chemical polishing produced uniform surface reduction over a large area.