Effects of Heat Treatment on Microstructure and Properties of Re/Inconel 718 Composites Fabricated by Laser Powder Bed Fusion

In this study, 3 wt.% Re/Inconel 718 composite was fabricated by laser powder bed fusion (LPBF), and the effects of aging treatments on the microstructure and properties of the Re/Inconel 718 composite were systematically investigated. This study aims to elucidate the synergistic optimization of microstructure and properties in LPBF Inconel 718, achieved through Re alloying and subsequent heat treatment. Results demonstrated that the samples undergo recrystallization and precipitate numerous fine strengthening phases after heat treatment. Concurrently, heat treatment promotes the diffusion of Re within the material, leading to a significant reduction in its concentration in locally enriched regions. The addition of Re improves the mechanical properties and corrosion resistance of the Inconel 718 alloy through synergistic strengthening mechanisms, including dispersion strengthening, solid solution strengthening, and dislocation strengthening. When the two-stage aging is 720 °C × 8 h (FC × 2 h) + 620 °C × 8 h (AC), the optimum mechanical properties are observed. The dissolution of Laves phases, simultaneous precipitation of both γ″ and γ′ phases, and homogenization of microstructure are responsible for the enhancement of the material’s mechanical properties. However, the extensive precipitation of strengthening phases also promotes the formation of numerous microscopic corrosion cells, which accelerates the corrosion rate and leads to a marked reduction in corrosion resistance of the material. This study provides new insights into the laser additive manufacturing of high-performance nickel-based composites.