Geometric design-driven mechanical enhancement and elevated-temperature performance of SLMed ODS-IN718 lattice structures

This study investigates the mechanical performance of selective laser melting (SLM)-fabricated oxide dispersion strengthened (ODS) IN718 superalloy lattice structures, focusing on structure optimization and high-temperature behavior. Two novel lattice designs, Anchor-FCC (A-FCC) and Notch-Reduced-Anchor-FCC (NRA-FCC), were developed via topology modification and tensile triangle method (TTM)-based notch reduction to enhance the load-bearing efficiency of conventional F2BCC lattices. Remarkably, the NRA-FCC lattice achieved a 48% strength improvement and a 13.8% relative density reduction compared to F2BCC, demonstrating significantly enhanced load efficiency. Specimens of IN718 and Yttria-doped ODS-IN718 were fabricated via SLM and evaluated through analytical modeling, finite element simulations, and mechanical testing, with actual printed lattices exhibiting ∼35% higher relative density than designed due to manufacturing imperfections. Compressive tests at 650°C revealed a critical performance discrepancy: while bulk ODS-IN718 exhibited enhanced strength (14.1% increase in yield strength and 10.8% increase in tensile strength) and ductility (8.8% increased elongation), its lattice counterparts showed diminished mechanical properties. This unexpected degradation is attributed to stress concentration and microcrack propagation exacerbated by SLM-induced ceramic phase impurities (∼40 μm), identified via microstructural analysis, in contrast to the intended uniform dispersion of 40 nm Yttria nanoparticles. This work highlights the critical role of tailored topology and notch design in achieving substantial performance gains (e.g., 48% strength increase) and uncovers the challenge of translating ODS superalloy benefits to complex lattice architectures at high temperatures due to impurity-induced damage mechanisms. Findings provide crucial insights for advancing high-temperature applications of additively manufactured ODS alloys through integrated geometric and process optimizations.