Beam Based and TPMS Lattice Structures in Inconel 718: An In-Depth Comparative Analysis of Manufacturability Through L-PBF and Metallographic Characterization

This study explores the application of lattice structures as internal support architectures in the fabrication of Inconel 718 components via Laser Powder Bed Fusion (L-PBF), building upon previous research on beam-based FCCZ supports. Two representative lattice typologies were investigated: the node and beam-based FCCZ structure and the triply periodic minimal surface (TPMS) Schoen Gyroid cell. The aim was to assess how the transition from a discrete beam-node architecture to a continuous surface topology influences manufacturability, thermal stability, and mechanical performance. Finite Element Method (FEM) simulations in Ansys accurately predicted distortions and residual stresses during the L-PBF process, showing strong agreement with stereomicroscope measurements. After fabrication, the samples underwent solution treatment and double aging according to AMS 2774 and AMS 5662 standards. Microstructural analysis using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that heat treatment partially homogenized the microstructure but did not achieve complete recrystallization, leaving localized dendritic regions and undissolved Laves phases, particularly near the lattice. The precipitation of γ′ and δ phases enhanced hardness and mechanical uniformity, as confirmed by Vickers microhardness testing. Overall, the Gyroid topology demonstrated superior manufacturability and thermal stability, exhibiting reduced defects and deformation compared to the FCCZ structure. These findings confirm its potential as an efficient and reliable self-supporting architecture for L-PBF Inconel 718 components intended for high-performance and thermally demanding applications.