Surface texture optimization of IN-625 additive manufactured components for optimal mechanical performance

In the past few years we have experienced a growing demand for surface finishing of IN-625 additive manufactured (AM) components in the aerospace industry. AM produced components have an intrinsic problem—their surfaces are extremely rough and packed with multiple layers of partially melted/sintered powder and significant defects. Moreover, recent high resolution X-ray CT scan data has shown a great deal of porosity packed at the near-surface, around 150 microns from the surface. In order to be approved for aerospace applications, AM-built parts need to be surface finished to remove their “as-produced” surface roughness and meet the requirements of the industry. There is a clear need for new surface finishing (post-processing) techniques capable of not only improving the appearance of the AM produced components, but also that are capable of removing all the surface and near-surface defects, while improving the mechanical strength of the components. In order to address this need we have developed a new AM program based on their already existing technology ISF® (isotropic superfinishing) process. We will discuss how the ISF® process for IN-625 components can be utilized to overcome the challenges to produce surface-finished components that meet the standards of the industry. So far the process has been shown capable to remove up to 200 microns of metal surface, eliminating the surface and near-surface defects of the components. We have processed uniaxial tensile fatigue specimens that are to be tested and presented on the as-built and the processed components. Three different surface finishing operations were performed to improve the surface of the fatigue specimens (electropolishing, chemical milling and ISF®, and the combination of two or more of them). The surface finished components, high resolution X-ray CT-scan and the fatigue data are going to be presented.