<p>This study investigated the microstructure and mechanical behavior of bimetallic components made from Grade 91 steel and Monel 400, fabricated using Wire Arc Additive Manufacturing (WAAM). The analysis revealed a tempered lath martensite structure in Grade 91 steel, enhanced by fine M₂₃C₆ carbides and MX-type precipitates, contributing to its high strength. Monel 400 exhibited uniform equiaxed grains, indicating good mechanical stability. At the bimetallic interface, a distinct boundary without defects was observed, suggesting a robust metallurgical bond. Residual stress analysis showed tensile stresses in Grade 91 steel and compressive stresses in Monel 400 due to their differing thermal properties. Tensile tests combined with Digital Image Correlation indicated that both materials retained their intrinsic ductility and strength, with localized strain leading to necking and ductile fracture. The bimetallic interface demonstrated improved mechanical properties and good bonding strength, validating WAAM’s efficacy in producing bimetallic structures. The study confirms that WAAM effectively produces bimetallic structures with enhanced mechanical properties, suitable for high-performance industrial applications such as heat exchangers and petrochemical, marine, and automotive industries.</p> Graphic Abstract <p></p>