AM surfaces tend to be rougher compared to conventional processes. Rougher surface finishes reduce fatigue strength compared to polished samples. Additive parts can be machined, ground, honed or polished to enhance the surface roughness, measured as Ra, or other surface finish attributes. Isotropic superfinishing processes might allow surface finish improvements without alterations to the geometry of the additive manufactured-parts. Extrusion honing or abrasive flow machining could be used to refine the surfaces of internal channels or hollows.
In the NASA technical report “Additive Manufacturing Overview: Propulsion Applications, Design for and Lessons Learned” by Kristin Morgan, engineering project manager from the NASA Marshall Space Flight Center, the fatigue performance of selective laser melted 718 nickel-based alloy (UNS N07718) was determined after various post-build surface finish enhancement treatments. Low-stress ground samples were the closest to approach the properties of the MMPDS design values for NO7718.
In the NASA technical report “Additive Manufacturing Overview: Propulsion Applications, Design for and Lessons Learned” by Kristin Morgan, engineering project manager from the NASA Marshall Space Flight Center, the fatigue performance of selective laser melted 718 nickel-based alloy (UNS N07718) was determined after various post-build surface finish enhancement treatments. Low-stress ground samples were the closest to approach the properties of the MMPDS design values for NO7718.