Cold spray additive manufacturing of Inconel 718/Cu and Inconel 718/GRCop-42 multi-materials: effects of deposition sequence on interface and thermal conductivity

Fabricating high-performance Inconel 718 (IN718) multi-material structures with high-conductivity copper alloys is critical for advanced thermal management applications, yet controlling interfacial thermal transport remains a significant challenge. This study systematically investigates the role of deposition sequence and post-processing heat treatment on the interfacial microstructure, and thermal conductivity of IN718–Cu and IN718–GRCop-42 joints fabricated via Cold Spray Additive Manufacturing (CSAM). Directional heat transport was isolated by evaluating in-plane conductivity via the Transient Plane Source (TPS) method and through-plane conductivity via Laser Flash Analysis (LFA). The results show that deposition sequence strongly affects the dominant heat-transport mechanism: the Cu/IN718 configuration yielded a superior in-plane thermal conductivity of ∼170 W/m·K by bypassing interfacial boundaries, whereas through-plane transport across all configurations was severely constrained by interfacial thermal resistance in the build direction. Furthermore, a standard two-step aging treatment induces a remarkable 131% increase in the in-plane thermal conductivity of GRCop-42/IN718 joints (from 48 to 111 W/m·K), driven by localized microstructural evolution within the copper-alloy regions, showing grain coarsening and reduction in Kernel Average Misorientation (KAM), indicating stress relief and defect recovery. Overall, this work clarifies how deposition sequence and post-deposition heat treatment govern interfacial quality and thermal performance in CSAM-fabricated Ni-based/Cu-based multi-materials