A novel approach towards the fabrication of SS316L–IN718 multi-metallic components using AM lattices and powder metallurgy

Abstract

The present study investigates a novel hybrid manufacturing route by synergistically integrating additive manufacturing (AM) and powder metallurgy (PM) to fabricate multi-material metallic components. In this approach, Inconel 718 (IN718) lattice structures were fabricated using Laser Powder Bed Fusion (LPBF), serving as geometrically constrained mould filled with SS316L powder, which was uniaxially compacted and sintered at varying temperatures. IN718–SS316L specimens were analysed for bonding, compatibility and interfacial integrity across sintering temperatures from 1100 °C to 1250 °C. The investigation revealed that elevated sintering temperatures promote interdiffusion of Fe and Ni, as confirmed by EPMA elemental mapping, while also enhancing neck growth and interface consolidation. However, common defects such as partially sintered or unsintered powder, porosity, interfacial cracks and localised over-melting were observed, especially at sub-optimal or excessively high temperatures. Specimen sintered at 1250 °C demonstrated the most uniform bonding with minimal crack density (15.0 cracks/mm²) and the lowest porosity. After polishing, pores ranging from 25.00 μm to 175.05 μm were still predominantly located within the SS316L regions, rather than at the IN718–SS316L interface. The microhardness at the IN718–SS316L interface was measured at 275 ± 4.8 HV, a 30.95% increase compared to typical values reported for conventionally sintered SS316L (∼210 HV). Meanwhile, the IN718 nodal region showed a microhardness of 305 ± 5.5 HV, indicating a well-preserved mechanical profile. The process enables tailored material integration, and with further optimisation in filling strategies, compaction and thermal profiles, offers a promising route for structural applications with graded material properties.