Interfacial Microstructure and Mechanical Performance of Stainless Steel—Low Alloy Steel Bimetallic Structures Fabricated by Wire Arc Additive Manufacturing

Abstract

Bimetallic structures (BMSs) are being used more frequently in industries like automotive, aerospace, and shipbuilding because they combine different material properties in a single component. Traditional methods like welding and brazing have their limits, but additive manufacturing (AM) offers a more flexible and cost-effective way to create complex multimaterial parts. This study focuses on the microstructure and mechanical properties of BMSs made by depositing stainless steel (SS) on high-strength low-alloy (LA) steel using the Wire Arc Additive Manufacturing (WAAM) process with Surface Tension Transfer (STT). The results show that defect-free BMSs can be successfully fabricated, improving design possibilities. Microstructural analysis revealed a clear Ferrite-Austenite (FA) boundary at the SS-LA interface. Key findings include an 81.81% increase in hardness at the interface relative to the LA steel side, along with an interface tensile strength of 621 ± 7 MPa and elongation of 19.28% ± 1.76%. Electron backscatter diffraction (EBSD) showed fine, randomly oriented grains in the SS region and elongated, directionally aligned grains in the LA region, with no dominant texture, indicating near-isotropic behavior. The presence of both low-angle and high-angle grain boundaries confirmed dynamic recrystallization during deposition. Fracture analysis showed strong mechanical bonding, with failure mainly occurring on the LA side. This demonstrates that WAAM with STT is a viable method for creating reliable, high-performance multimaterial components.