Laser-directed energy deposition as a promising dissimilar joining technique: A case study on SS316L and IN718 with CoCrFeNi-based fillers

Dissimilar metal joining is widely used in the automotive and aerospace industries for weight reduction and alloy integration. In this study, CoCrFeNi high-entropy alloy (HEA) and CoCrFeNi +TiB₂ were employed as fillers to join stainless steel 316 L and Inconel 718 using laser-directed energy deposition (L-DED). The rapid cooling and localized melting in L-DED suppressed intermixing, interdiffusion, and the formation of large brittle intermetallics while leading to negligible heat-affected zone. The addition of TiB₂ microparticles to the CoCrFeNi HEA filler refined the microstructure and improved mechanical properties. TiB₂, acting as a reactive inoculant, decomposed during the process to form Cr-rich and Ti-rich inter-dendritic cellular structures, enhancing the hardness and tensile strength of the weld zone, and the ductility of the joined parts. The combined use of L-DED and reactive inoculants demonstrates the potential to expand material options for dissimilar metal joining, enabling stronger and tougher weld zones for advanced engineering applications.