Printability and Characterization of Fused Deposition Modeling-Based Bimetallic Metal Additive Manufacturing (AM) of Inconel 718 and Stainless Steel 316L: Democratization of Metal AM

Abstract

Metal additive manufacturing (AM) provides opportunities for producing complex metallic components. However, many conventional metal AM systems require high capital investment, specialized facilities, and energy-intensive processing. As an alternative, material extrusion-based metal AM using metal-filled filaments offers a more accessible route for fabricating metallic parts and exploring multi-material or hybrid structures. This study examines the feasibility of producing bimetallic components using Inconel 718 (IN718) and Stainless Steel 316L (SS316L) through a fused deposition modeling(FDM)-based print-debind-sinter process. Bimetallic rectangular and tensile specimens were fabricated using a dual-extrusion system by depositing the two metal-filled filaments in an alternating layer configuration. The printed green parts were then subjected to thermal debinding and sintering under different processing conditions. The fabricated specimens were evaluated in terms of printability, dimensional change, density, surface quality, phase formation, microstructural development, elemental distribution, and tensile performance. The results showed that the selected extrusion-based process could produce stable green parts and maintain the overall specimen geometry after post-processing. Increasing sintering duration improved densification, reduced porosity, and enhanced microstructural consolidation. Phase and microstructural analyses indicated the development of a predominantly metallic matrix with secondary phase formation influenced by sintering condition. Elemental mapping confirmed that the two alloy regions retained compositional distinction and showed evidence of interfacial diffusion, suggesting metallurgical bonding between the materials. Geometric analysis revealed noticeable shrinkage after sintering, highlighting the importance of dimensional compensation in extrusion-based metal additive manufacturing. Mechanical testing further showed that tensile behavior was influenced by both sintering condition and deposition orientation, with improved strength observed under selected processing conditions. Overall, this research demonstrates the technical feasibility of fabricating IN718-SS316L bimetallic structures using a low-cost material extrusion-based metal AM route. The findings indicate that final part quality and performance are strongly affected by densification behavior, interfacial bonding, microstructural evolution, phase development, surface characteristics, and shrinkage compatibility. This work contributes to the broader understanding of accessible bimetallic metal AM and provides a foundation for future optimization of process parameters, material combinations, and post-processing strategies.