Microstructural evolution and mechanical properties of Inconel 625-316L steel Bbmetallics produced by Wire + Arc additive manufacturing: Challenges and solutions

This study investigates the microstructural evolution and mechanical properties of Inconel 625-316L bimetallic materials fabricated using Wire + Arc Additive Manufacturing (WAAM). The Inconel 625-316L steel bi-metallic material has significant applications in aerospace, automotive, and power generation industries, with unique and enhanced mechanical properties with both strength and ductility. The deposition sequence and grain orientation of Inconel 625-316L steel bi-metallic material significantly influenced the interface thickness, crack formation, and mechanical performance. The fabrication of Inconel 625-316L Steel Bi-metallic materials was carried out through a layer-by-layer deposition process using two Kemppi double pulse X8 MIG Welders. Hardness and tensile tests were conducted to evaluate the mechanical properties of the fabricated samples. The results revealed that the bi-metallic material exhibited higher hardness (35.62 ± 0.855 HV) compared to the parent materials, though their tensile strength was lower. High-resolution scanning electron microscopy (HRSEM) and energy dispersive spectroscopy (EDS) analyses identified Solidification cracks near the 316L steel/Inconel 625 interface, with second-phase particles detected close to the Inconel 625 material. Notably, misaligned grain orientations resulted in a thicker interface, whereas aligned orientations led to a thinner and more crack-prone interface. These findings highlight that interface characteristics significantly impact mechanical performance by influencing crack susceptibility and interfacial bonding. This study provides critical insights for improved structural integrity in aerospace, nuclear, and industrial applications.