Unlocking superior fatigue performance in nanoparticle metal material jetted 316L stainless steel

• Metal material jetting (MMJ) enables refined SS316L microstructures. • MMJ 316L shows up to 16× improvement in fatigue life over binder jetting. • Grain refinement enhances crack growth resistance. • Fatigue limit predicted via hardness–defect model within ∼5 % error. • MMJ offers high fatigue resistance for structural materials applications. This study explores the fatigue performance of novel metal material jetting (MMJ), a process that uses sub-micron powders to induce significantly refined microstructures compared with other sinter-based additive manufacturing (AM) technologies such as metal binder jetting (MBJ). Stainless steel 316L (SS316L) samples fabricated via MMJ were subjected to fully reversed uniaxial cyclic loading to generate a stress-life (S/N) curve, which was compared to literature data for MBJ SS316L. The fatigue performance of MMJ SS316L was markedly superior to MBJ, with as much as 16× improvement in the number of cycles to failure in the low cycle fatigue regime and 14× in the high cycle fatigue regime. This enhancement was attributed to the inherent smaller grains, leading to a high density of high-angle grain boundaries and annealing twins that improved resistance to crack initiation and propagation. A mechanics-based model incorporating hardness and defect size was used to estimate the fatigue limit, yielding a ∼5 % error compared to experimental values. These results underscore the influence of finer microstructural features and defect distribution on fatigue performance in sinter-based AM and highlight MMJ’s potential for structural applications requiring high fatigue resistance