Thin-Wall Internal Microchannels and Surface Enhancements for Rocket Nozzles using Laser Powder Directed Energy Deposition

Laser Powder Directed Energy Deposition (LP-DED) is maturing as a method for producing thin-wall, complex components for extreme environment applications such as liquid rocket engine heat exchangers. A key advantage of LP-DED is its ability to fabricate parts over 2 meters in diameter while incorporating fine internal features, enabling part consolidation. However, successful implementation requires detailed characterization of as-built geometries and potential post-processing improvements, particularly for surface texture. Surface texture—including roughness and waviness—is a critical attribute in additive manufacturing that influences pressure drop, service life, and heat transfer in heat exchangers. Yet, limited data exists for LP-DED in this context. This presentation shares lessons learned and Design for Additive Manufacturing (DfAM) principles for LP-DED, focusing on thin walls and small channel geometries representative of high-performance alloys such as NASA HR-1, Inconel 625, A6061-RAM2, and GRCop-42. We will present an overview of experiments conducted using varied LP-DED parameters, including the characterization of internal channel geometries, geometric build features, and resulting surface textures. Post-processing techniques for surface enhancement were evaluated and paired with flow testing to assess their effects on friction factor and performance. The work characterizes microchannels produced by LP-DED, identifies mechanisms driving surface texture—such as powder adherence, material droop, and angled wall effects—and discusses their design implications. Results demonstrate how tailored surface enhancements can tune wettability for improved friction, heat transfer, or fatigue performance. Overall, the findings support LP-DED as a viable fabrication method for high-performance heat exchangers, addressing challenges in geometry, wall thickness, surface quality, and fluid dynamics.