Surface Finishing Guidelines to Yield Ready-to-Use Additive Manufacturing Metal Components with Superior Fatigue and Corrosion Resistance Properties

The surface-related defects (SRD) that metal additive manufactured (AM) components show, compromising their structural integrity, have historically hampered its real potential. A surface finishing process(es) is needed to remediate these defects, maximizing AM's potential in all industries. Secondary subtractive finishing processes such as grinding, electropolishing, and abrasive tumbling, may be used to remove some of these defects. Nevertheless, the efficacy of these subtractive technologies to finish AM components is extremely limited due to the geometrical complexity, size, and line-of-sight inaccessibility characteristic of AM components. As a result, AM requires alternative surface finishing techniques to reach its full potential. We will discuss a surface finishing technology capable of addressing all these drawbacks in a two-step process during this presentation. The initial step involves removing the macro defects from the surface and near-surface via chemical polishing. The second step consists of using a chemical-mechanical polishing approach to achieve optimal surface planarization, producing remarkably low surface roughness values. The processed metal AM components showed a surface roughness of 0.8 μm or lower, uniformly SMR from the internal and external surface of geometrically complex components, and the elimination of SRD, improving the mechanical and corrosion-resistant properties of the components significantly. In addition, the high cycle fatigue and corrosion-resistance samples treated with two different HIP'ing approaches (standard vs. uniform rapid cooling/quenching) and their implications in combination with the developed surface finishing technology were also investigated. This work was supported in part by NASA-MSFC SBIR Phase-I, II, and III: "Post-Process Optimizing of Additive-Manufactured Nickel-Based Superalloys" (Z3.01-5453); AFWERX-OO-ALC SBIR Phase-I: "Internal/External Surface Finishing of Additively Manufactured Aluminum-6061-RAM2 Components" (FA864920P0930) and Phase-II: "Internal/External Surface Finishing of Additively Manufactured Aluminum-Based Components" (FA864921P0815); and AFWERX-AFLCMC/EBW SBIR Phase-II (direct): "Development of Manufacturing, Heat Treatment, and Surface Finishing Guidelines to Yield Ready-to-Use IN-718 Additive Manufacturing Components" (FA864921P0854). Special thanks to Quintus Technologies.