Mechanical and metallurgical characterization of hybrid carbon steel combining hot-rolled and WAAM

The integration of Wire Arc Additive Manufacturing (WAAM) with conventional steel manufacturing methods presents a transformative approach to structural engineering, offering a balance between geometric freedom, production speed, and economic viability. While WAAM enables the production of complex (i.e., optimized geometries), its widespread adoption is currently hindered by lower productivity and higher costs compared to traditional rolling or cold-forming processes. This paper explores the concept of hybrid construction, where WAAM is strategically deposited onto conventional structural steel substrates to create high-performance components superior to conventional members. The applicability of this concept is demonstrated through various scenarios, by the analysis of fabricated hybrid hot-rolled WAAM walls varying the process parameters and steel substrate grade. Since one of the most critical aspects of hybrid systems is the interface between the deposited WAAM material and the base substrate, this study evaluates the microstructural and hardness evolution at the bi-metal interface, integrating uniaxial tensile and Charpy V-notch impact tests to assess the structural performance of the hybrid components. It is observed that the thermal gradients inherent to the process are governed by parameters such as interlayer temperature and heat input, changing the microstructure and increasing mechanical properties of the interface region. Moreover, through optimizations in the combination of process parameters and steel substrate grade, the location of a failure and a match regarding material properties can be achieved. In addition, numerical simulations are performed to verify and assess deeply these concepts. The findings confirm that, with precise control of printing strategies, hybrid components can achieve superior material and structural efficiency, validating the potential of this technology for future applications in the construction sector.