Thermal Expansion and Microstructure of Laser Additively Manufactured Inconel 617 for Small Modular Reactors

Inconel 617 (IN617) is a nickel-based superalloy with excellent high-temperature properties and corrosion resistance needed for high-temperature gas-cooled small modular reactors. In this study, IN617 parts were fabricated by laser-beam powder bed fusion (PBF-LB) and laser-beam directed energy deposition (DED-LB) additive manufacturing (AM) processes using various process parameters. The coefficient of thermal expansion (CTE) of AM samples was measured using the push-rod dilatometry method up to 1100°C and high-temperature 2D X-ray diffraction experiments up to 900°C. At temperatures below 200°C, the samples showed a non-uniform variation in the CTE due to the presence of lack-of-fusion pores. At temperatures above 800°C, there was a uniform increase in CTE for the samples fabricated with a medium-energy input. The PBF-LB sample showed a CTE of 16.04 × 10−6 1/°C, while the DED-LB sample had a CTE of 16.56 × 10−6 1/°C at 1000°C. This difference in CTE is likely attributed to the variation in the relative density, with the DED-LB part showing a higher value of 98.44% compared with the PBF-LB part that showed 97.50%. These thermal property data align with the thermal properties of wrought IN617, validating AM as a viable technique for nuclear applications.