Additively Manufactured Heat Exchanger and Channel Fabrication Optimization via Chemical Powder Blockage Removal, Surface Roughness Reduction, and Wall Thickness Optimization/Component Lightweighting

N. Michaud, R. Shealy
REM Surface Engineering,
United States

Keywords: additive manufacturing, postprocessing, surface finishing, IN-718, F357

Summary:

Metal Additive Manufacturing (AM) is a game-changing component fabrication technology. Heat exchangers, components with integrated cooling channels, lattice structures, and similar, complex or even impossible to produce via traditional, subtractive techniques can readily be produced via laser powder bed fusion (L-PBF) based AM processes. However, there are considerable difficulties in removing powder from internal channels and cavities, which can lead to costly, manual, and/or unreliable powder removal processes. Further, for highly complex components, powder removal may be impossible via these manual methods resulting in the scrapping of expensive components and the loss of many manufacturing and labor hours. Moreover, in many instances components have to be modified from the optimal design to allow for powder removal, hampering the full potential of AM. In addition, as-printed components are known to have high levels of surface roughness and to commonly suffer from concentrations of near-surface porosity, sometimes referred to as surface-related defects (or SRD’s). These SRD’s can produce non-optimal fluid flow performance, increase foreign object debris (FOD) risks/create cleanliness challenges, and serve as surface/near-surface fatigue failure initiation sites. Lastly, for some applications, especially those involving thermal transfer mechanisms, the optimal wall thickness cannot be reliably produced with current AM technologies. This manufacturing limitation can further manifest as limitations on potential component lightweighting efforts. During this SBIR Phase II effort with Ogden Air Logistics Complex (OO-ALC), REM will address the need for a robust manufacturing technology that can address these current AM limitations. Such a process would significantly aid in the actualization of AM’s many benefits for both defense sustainment and readiness goals. Additionally, such a process will be critical for advanced component generation via AM in the pursuit of hypersonic and other strategically important applications. To meet these needs, REM is developing a chemical process to address these known AM limitations with deliverables of being able to remove trapped powder for internal channels/cavities in a controlled fashion, and to subsequently reduce surface roughness/eliminate SRD’s from these same channels/cavities. Additionally, this process will be designed such that it can uniformly reduce wall thickness so that walls can be printed to thicknesses with good material properties and a high degree of manufacturability, and subsequently, they can be controllably reduced to desired thicknesses to improve thermal transfer properties and/or reduce component weight. Metal additive manufacturing is revolutionizing manufacturing via the reduction of operational steps, component lead time, and component cost. Of particular interest to the aviation industry is the manufacturing of legacy components to address sustainment and readiness challenges associated with a dwindling supply base, high costs, and long lead times. These capabilities make AM an important technology for the US Air Force and industry. By addressing the limitations listed above in an effort to help the AF realize the benefits of AM – increased Operational Availability at reduced total lifecycle costs.