Additive Manufacturing of a High Temperature, Ni-Based Superalloy Compact Heat Exchanger: A Study On the Role of Select Key Printing Parameters


 Compared to state-of-the-art heat exchangers, manifold-microchannel heat exchangers (MMHX) have shown superior heat removal density at moderate pressure drops. However, MMHX made of Ni-based superalloys or other tough-to-machine materials can be a challenge to fabricate using conventional fabrication methods, because of the inherently complex manifold microchannel geometry, as well as the required small feature sizes. In this study, a direct metal laser sintering (DMLS) additive manufacturing (AM) technique was used to fabricate the compact high-temperature MMHX reported here. The AM MMHX was fabricated as a single object, which significantly simplifies the fabrication process. In this work, three different AM machines were used to study the effect of laser power, powder size, and layer thickness on the fin and channel sizes of the fabricated MMHX. To evaluate the minimum wall thickness able to hold the design pressures, pressure containment tests were performed. As a result, a wall thickness of 0.3 mm was shown to withstand 340 kPa and be leakage-free. A detailed analysis of different printing orientations and their effect on the MMHX's design was also performed. Lastly, a 76×76×76 mm3 MMHX was successfully fabricated with fin thickness of 0.13 mm out of maraging steel. A second unit with dimensions of 94×87.6×94.4 mm3 was successfully fabricated with fin thickness of 0.22 mm out of Inconel 718. Details of the fabrication process and key takeaway results are discussed.