Additive Manufacturing of Metal Matrix Composite Heat Exchangers

Heat exchangers have the capability to solve thermal management challenges in hypersonic and space systems. However, problems with manufacturing (brazing or welding) and material degradation can affect heat exchanger performance and the feasibility of future complex designs. The proposed work explores making heat exchangers with an additive manufacturing (AM) process and a high temperature metal matrix composite. The potential impact of the proposed work will influence two markets that are expected to reach $40B in 2030, and the potential technology revenue for 2030 is expected to reach $900M based on market trends in the heat exchanger industry.  The Problem: Heat exchangers are critical components for hypersonic and space applications. Hypersonic engines use heat exchangers to improve thermal efficiencies, and space systems like the International Space Station (ISS) use heat exchangers to tune heat rejection and make the crew’s environment habitable. However, the main heat exchanger manufacturing process of brazing is complex and can lead to issues such as eutectic interfaces and oxidation. Both issues can lead to low strength in the structures and leaks from lack of fusion. A desirable alternative to brazing is the laser powder bed fusion (LPBF) AM process. Though AM enables the consideration of complexity for more efficient heat exchangers with novel alloys, achieving thin walls, small flow channels, component strength, and minimizing leakage are challenging. Additionally, repeatable manufacturing of materials with high thermal conductivity is a challenge for LPBF. The manufacturing obstacles associated with heat exchangers must be addressed to advance hypersonic and space system technologies.  Proposed Solution/Innovation: This project will explore the manufacturability of a carbon nanotube (CNT) strengthened nickel alloy via the LPBF AM process. This work aims to address the Air Force and Space Force needs of cooling future hypersonic systems and regulating temperatures for space structures. The nickel alloy of interest is an AM specific CNT Haynes 230, which was previously developed and demonstrated through an Air Force contract (FA864922P0751). The Phase I for the proposed work will focus on developing process parameters and understanding the LPBF manufacturability of thin structures and key heat exchanger component features. In addition, the strength of the LPBF structures at temperature will be assessed. Phase II expects to extend the heat exchanger manufacturability of CNT Haynes 230 via LPBF to the full components of interest for NASA Johnson and a GoHypersonic applications. The work in Phase II is expected to demonstrate high strength at temperature, component pressure capability, and improved thermal conductivity compared to traditional nickel alloys.