Multi-material additive manufacturing of 316L and 17-4 PH steels: Interface comparison between two distinct technologies

Additive manufacturing (AM) offers unique flexibility for designing architectured and complex-shaped parts. While current research largely focuses on optimizing the spatial distribution of material and void, the potential of AM for integrating complex phase or composition distributions within a single component remains largely underexplored. Yet, this approach opens up new pathways for developing composite or functional materials with locally tailored properties. This study explores the fabrication of multi-material parts where one metallic alloy is directly deposited onto another during the additive process, combining two contrasting stainless steels: 316L (austenitic) and 17-4 PH (martensitic). Their similar chemical compositions reduce the risk of brittle intermetallic formation at the interface, while their distinct mechanical properties allow for an effective property trade-off. Two radically different AM processes are compared: an indirect process based on metal extrusion followed by sintering (Metal Extrusion Additive Manufacturing), and a direct wire-based laser fusion process (Wire Laser Additive Manufacturing). The former promotes interfacial bonding through solid-state diffusion, while the latter induces partial dilution between the two materials. Through a multi-scale analysis of porosity distribution, chemical element partitioning, microstructural evolution, and local mechanical properties, we investigate the interfacial characteristics obtained for each process. Particular attention is given to the thickness of the interface, which is controlled by the diffusion behavior specific to each process. This comprehensive approach aims to reveal the key mechanisms governing interfacial behavior and to develop optimized design strategies for multi-material AM. Ultimately, after interface optimization, global mechanical tests such as tensile testing will be carried out as part of future work to evaluate the overall structural performance.