Thermal and Microstructural Characterization of GRCop-84/In718 Bi-metallic Structures Additively Manufactured by Directed Energy Deposition

Abstract

As a nickel-based super alloy, Inconel 718 (In718) has gained attention in different industries due to its excellent mechanical behavior under elevated temperatures. Nevertheless, its low thermal conductivity limits its application in many fields, such as thermal energy conversion and heat dissipation. GRCop-84, in contrast, is a copper-based alloy with extremely high thermal conductivity. Making bi-metallic structures with GRCop-84 may expand the thermal-related applications of Inconel 718. In this study, we investigate the thermal properties of In718/GRCop-84 bi-metallic structures fabricated by the directed energy deposition (DED) technique with different process parameters of laser power and scanning velocity. The resulting microstructures were analyzed through scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), while the frequency-domain thermoreflectance (FDTR) technique has been adopted to acquire the thermal properties. The melt pool thermal conductivities were 50 W/m K on single bead samples and 100 W/m K on single-layer pads, significantly lower than that of bulk GRCop-84. EDS analysis reveals large deviations from standard GRCop-84 compositions inside the melt pool.