Recrystallization and Laves phase dissolution in PBF-LB/M Inconel 718 under different solution heat treatment routes followed by aging

Abstract

© 2026 The AuthorsInconel 718 is crucial in high-demand thermomechanical applications such as components of gas turbines and rocket engines. With an increasing need for complex parts, additive manufacturing, especially Laser Based Powder Bed Fusion of Metals (PBF-LB/M), has become a useful processing route for engineering components. However, the PBF-LB/M process generates out-of-equilibrium solidification, promoting segregation, residual stresses and undesired phases, which compromises mechanical properties, such as fatigue strength. For this reason, PBF-LB/M components usually require post-processing heat treatments. This study evaluates the effectiveness of different single solution heat treatments followed by aging in PBF-LB/M IN718. In addition to the conventional 980 °C-1 h solution treatment, two higher-temperature routes, 1065 °C-1.5 h and 1160 °C-4 h, were investigated as simplified single-step solution treatments prior to aging. The purpose was to assess whether these routes can promote Laves phase dissolution, recrystallization, residual stress modification and acceptable mechanical response without requiring an additional solution heat treatment. It was observed that solution heat treatments at 1065 °C for 1.5 h and 1160 °C for 4 h resulted in recrystallization, with the latter condition even displaying grain growth and high compressive residual stresses at the surface. The conventionally treated condition at 980 °C for 1 h exhibited higher hardness and tensile strength due to increased dislocation density and presence of both Laves and δ-phase. However, even though the conditions at 1065 °C-1.5 h and 1160 °C-4 h present higher tensile strength than the wrought material, it still lacks ductility compared to the wrought material. It is concluded that both solution heat treatments at 1065 °C-1.5 h and 1160 °C-4 h have reached recrystallization and stress relief. Overall, the 1065 °C-1.5 h and 1160 °C-4 h routes showed potential as simplified solution heat treatments followed by aging, producing recrystallized, nearly texture-free and stress-relieved microstructures while retaining significant tensile strength.

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