Fabrication of a Transformative Compact Heat Exchanger for High-Temperature Supercritical CO2 Power Generation by Powder Bed Fusion

Abstract Powder bed fusion (PBF) additive manufacturing (AM) has garnered significant interest in nickel (Ni)-based oxide dispersion-strengthened (ODS) alloys to achieve enhanced performance of a heat exchanger at elevated temperature. However, achieving a uniform distribution of strengthening nanoparticles throughout the metal matrix has proved to be a challenge for many researchers. This study, hence, focuses on the processing of yttria (Y2O3) nanoparticles added to Haynes 214, a Ni-based alloy, with the laser PBF process. The optimization of the PBF processing window was systematically conducted to create near-dense coupons. Agglomeration of yttria nanoparticles and formation of an extensive network of cracks were observed in the ODS versions. Two strategies, (a) feedstock powder preparation using ball milling and (b) laser remelting, were found to be effective in achieving the homogeneous dispersion of nanoparticles as well as preventing crack formations. For each feedstock powder, tensile testing coupons were produced using the optimized processing parameters, and high-temperature (1000 and 1100 °C) mechanical testing was conducted. The effect of Y2O3 addition on the high-temperature tensile properties of Haynes 214 was investigated.