Session: 03-03-03: Annual Congress-Wide Symposium on Additive Manufacturing III

Paper Number: 172952

Introducing Interlayer in Additive Joining of Copper–stainless Steel Using Wire Arc Additive Manufacturing 

A major challenge in the additive joining of dissimilar metals is managing atomic diffusion at the interface. This diffusion can lead to the formation of brittle intermetallic phases, which may result in hot or cold cracking failures. These problems are primarily caused by the elemental diffusion along grain boundaries, which affects the additive joint structural integrity. The motivation of the study is to investigate additive joining that combines the thermal conductivity of copper and the mechanical strength of stainless steel, while overcoming the inherent challenges of joining such dissimilar materials. This work contributes to the field of additive joining by developing a robust methodology for fabricating copper–stainless steel Functionally Graded Materials (FGMs) via wire arc additive manufacturing (WAAM). The introduction of tailored interlayer materials acts as a metallurgical barrier, effectively mitigating thermal residual stresses, suppressing interdiffusion and brittle phase formation, and thereby enhancing the structural integrity of the dissimilar metal interface.

The experimental methodology involved the use of three sequential wire feedstocks: copper, various alloy interlayers, and stainless steel. Samples were fabricated using optimized WAAM parameters with controlled layer thicknesses and varied tool paths, while maintaining a consistent interlayer thickness. WAAM process parameters—including voltage, current, wire feed rate, torch travel speed, and build sequence—were systematically optimized to minimize thermal gradients and promote bi-metallurgical bonding. The fabricated materials were subsequently processed for detailed characterization using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to evaluate microstructure features and compositional gradients. Sample grinding and polishing with chemical etching were used to detect internal defects with an optical microscope, and mechanical performance was assessed through uniaxial tensile testing and hardness profiling across the build.

The results revealed a progressive microstructure transition across the layers. Microstructure analysis revealed that the build sequence plays a critical role in defining the interlayer morphology. When the interlayer was deposited onto the copper substrate, dendritic nickel-iron structures were observed at the interface, indicating elemental diffusion and directional solidification patterns. In the copper region, refined equiaxed grains were achieved, attributed to favorable thermal gradients and solidification dynamics. In the interlayer, martensitic transformation was detected, influenced by the underlying copper's high thermal conductivity. Increased heat input in subsequent layers led to grain coarsening, which caused localized strain accumulation and the initiation of intergranular cracking. Hardness profiling showed a uniform gradient in the monolithic regions, with gradual transitions from copper to stainless steel. These results validate the effectiveness of the interlayer additive joining strategy in suppressing abrupt dissimilar material property mismatches and provide a foundation for reliable additive joining of dissimilar materials.

Presenting Author: Chuankai Song Oregon Manufacturing Innovation Center (OMIC)-Oregon Institute of Technology

Presenting Author Biography: Dr. Chuankai Song is a Research Associate at OMIC R&D with a robust background in additive manufacturing gained during his Ph.D. studies at Oregon State University. He specialized in Mechanical Engineering, with minors in Materials Science and Industrial Engineering, and has extensively engaged in laser-based additive manufacturing technologies, including Laser Powder Bed Fusion (LPBF) and Laser-Directed Energy Deposition (LDED).

Authors:

Chuankai Song Oregon Manufacturing Innovation Center (OMIC)-Oregon Institute of Technology
Devyn Duryea Oregon Manufacturing Innovation Center (OMIC)-Oregon Institute of Technology
Kyle Mcgann Oregon Manufacturing Innovation Center (OMIC)
Trent Lamont Oregon Manufacturing Innovation Center (OMIC)
Sierra Repp Oregon Manufacturing Innovation Center (OMIC)
Will Watts Oregon Manufacturing Innovation Center (OMIC)
Dave Eames Oregon Manufacturing Innovation Center (OMIC)
Tai Adams Oregon Manufacturing Innovation Center (OMIC)
Zack Kane Oregon Manufacturing Innovation Center (OMIC)
Cole Erhardt Oregon Manufacturing Innovation Center (OMIC)
John Isherwood Oregon Manufacturing Innovation Center (OMIC)
Zane Strassheim Oregon Manufacturing Innovation Center (OMIC)
Mostafa Saber Oregon Institute of Technology