Metal additive manufacturing (AM) provides significant design flexibility, particularly for components with complex internal geometries such as heat exchangers (HEXs). Despite these advantages, trapped or caked powder and powder clogging continue to impede performance and widespread adoption. The trapped powder disrupts fluid flow, reduces cleanliness, and frequently obstructs internal channels, which can render components unusable. The lack of effective methods for removing trapped powder from enclosed features often leads to costly part rejections and accumulation of unrecoverable, high-value components. This study presents a two-step chemical process that selectively removes unfused powder and enhances internal surface quality without affecting the fused metal. The initial step utilizes a targeted chemical formulation that preferentially reacts with the powder, dissolving it while exhibiting minimal reactivity with the fused metal. Following powder removal, and if required for the component's intended application, a chemical polishing (CP) formulation is applied to reduce surface roughness further and improve fluid flow characteristics. The process has been demonstrated on PBF-LB/AlSi7Mg, AlSi10Mg, CP1, IN-718, and PBF-EB/Ti-6Al-4V components, including single and multi-channel test coupons, intricate gyroidal “challenge” structures, and fully functional HEXs. High-resolution X-ray CT scan was used to confirm the powder removal, significant reductions in SRDs, and restoration of channel flow. SAE AS4059 assessment for particle contamination count was used to verify part cleanliness. Results indicate measurable improvements in pressure drop, flow uniformity, cleanliness, and surface finish, with minimal material loss. This scalable chemical-flowing method addresses a persistent challenge in metal additive manufacturing, the removal of internal clogged or caked powder from complex internal cavities, while also improving surface integrity, if necessary. The technique demonstrates significant potential to reduce scrap rates, increase design flexibility, and enhance performance in aerospace and defense sectors. This research is supported by the United States Air Force (SBIR-FA864923P0707 and FA864922P0969).
Learning Objectives:
Attendees will learn how to remediate clogged powder by selectively chemical reactions towards the powder within internal cavities while preserving the integrity of the fused substrate.
Participants will learn how the CP process improves surface roughness, fluid flow, and performance of internal HX cavities, and other high-value components, improving high yield, scrap rates, and design freedom.
Participant will learn to evaluate the scalability of selective chemical treatments from heat exchangers to complex AM systems such as rocket nozzles, fuel injectors, and vanes with internal cooling channels.
