Effect of low-temperature gaseous carburizing on the compression behavior of 316 L lattice structures manufactured via laser powder bed fusion

• Stress–strain curves of BCC/diamond lattices before and after LTGC were obtained. • LTGC could significantly improve the mechanical properties of L-PBF 316 L lattice. • LTGC obviously influenced the deformation and failure modes of BCC/diamond lattice. • Effect of LTGC on the mechanical properties of lattice was quantitatively analyzed. • A mechanical model for lattice incorporating surface strengthening was established. Low-temperature gaseous carburizing (LTGC) was applied to enhance the mechanical performance of 316 L stainless steel lattice structures fabricated by laser powder bed fusion. The treatment generated a continuous carburized case uniformly covering all strut surfaces of both BCC and diamond lattices. Compression tests revealed LTGC substantially altered compressive behavior: originally smooth curves of as-built lattices exhibited fluctuations with distinct “peak-valley” characteristics after treatment. Furthermore, LTGC significantly enhanced yield strength, elastic modulus, plateau stress, and energy absorption. It also profoundly influenced deformation modes; BCC lattices showed density-dependent transitions from uniform deformation to localized shear banding, whereas diamond lattices exhibited localized failure. Analysis of the fracture mechanism revealed a distinct transition from ductile deformation to severe embrittlement governed by the carburized case and melt pool boundaries, altering the stress–strain response to a fluctuating profile. Quantitatively, LTGC had a greater enhancing effect on the yield strength and elastic modulus of BCC lattices, whereas energy absorption improvement was more pronounced for diamond lattices. This effect is determined by inherent lattice geometry and the competition between strength enhancement and induced brittleness. Finally, a mechanical model was established based on the strong linear correlation between the volume-to-surface-area ratio and mechanical enhancements.