Beam Based and Triply Periodic Minimal Surface 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), build-ing upon previous research on beam-based FCCZ supports. Two representative lattice ty-pologies were investigated: the node and beam-based FCCZ (face centered cubic with Z direction reinforcement struts) 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 sta-bility, 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. Specifically, the maximum di-rectional deformation reached 0.32 mm for the FCCZ sample versus 0.17 mm for the Gy-roid, with corresponding peak residual stresses of 1328 MPa and 940 MPa, respectively. After fabrication, the samples underwent solution treatment and double aging according to AMS 2774 and AMS 5662 standards. Vickers microhardness increased from about 320 HV0.3 in the as-built condition to 500 HV0.3 after heat treatment (+55%), with overall po-rosity remaining below 1%. Microstructural analysis using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) re-vealed 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 hard-ness and mechanical uniformity, as confirmed by Vickers microhardness testing. Quanti-tatively, the Gyroid topology exhibited approximately 40% lower deformation and defect density than the FCCZ structure, confirming its superior manufacturability and thermal stability. These findings provide practical guidance for selecting lattice topologies for sup-port architectures in L-PBF Inconel 718 components where thermal stability and shape preservation during build are critical.