A Novel Electrochemical Method to Reduce the Surface Roughness of Internal Features in Additive Manufactured Components

The proposed research is to evaluate and reduce the surface roughness of selective laser melting (SLM) manufactured components. Specifically, this proposal addresses the "Additive Component Internal Feature Surface Roughness Reduction" research priority set by the NASA Commercial Space Capabilities Office. The overall goal is to improve component fabrication for propulsion and power conversion applications. To meet this need, we propose a novel ultrasonic assisted electrochemical polishing approach, which is highly scalable, to reduce the surface roughness of internal features of components fabricated by SLM. We will devise an electrochemical setup in which the internal surface of the as-built component will act as an anode while a stainless steel rod will be the cathode. An optimized electrochemical solution will be developed depending on the material of interest. The internal surface will be electrochemically polished under ultrasonic agitation conditions using the setup developed in this research. During electrochemical polishing, different-sized electrochemical inert abrasive media, such as silicon carbide (SiC) and/or alumina (Al2O3), will be added to the electrochemical solution. Under the influence of ultrasonic agitation and electrochemical polishing conditions, these abrasive media generate a synergistic effect to remove the surface layer and thus efficiently reduce surface roughness. To obtain uniform surface roughness, we will intermittently rotate the setup 180 degrees counter-clockwise and clockwise. Surface roughness parameters will be measured using an optical profilometer after a selected number of cycles to determine the number of cycles required to achieve the desired roughness. The surfaces will be masked with polymeric material at locations where polishing is not required, such as channel inlets and outlets with sharp turns. After the desired roughness is achieved, the internal surface will be polished with fine abrasive media in deionized (DI) water followed by ethanol cleaning with an ultrasonicator to remove any residue. The post-fabrication step proposed here is unique and innovative in its use of tribocorrosion properties to reduce the surface roughness of the internal features of additive manufacturing (AM) metallic components. It is a simple and straightforward method that can easily be scaled up.

This is a mature technology (TRL 7+) — the realistic path in is usually NASA's Technology Transfer Program: licensing an existing NASA patent, or a Space Act Agreement to use NASA facilities/expertise directly. NASA also runs a startup licensing program with no upfront fee for companies formed to commercialize a specific NASA technology.

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