Selective crack propagation in steel-nickel component printed by wire arc directed energy deposition

Steel-nickel bimetallic structures exhibit attractive site-specific properties, but it is challenging to fabricate large a monolithic component while maintaining the dense regular interface that enable their properties. This study proposed a criss-crossed interface in steel (316L stainless steel) - nickel (IN 718 alloy) bimetallic component, with in-situ microstructure interlocking and improved mechanical response. A difference in physical properties between these two materials creates cracks at their interface where were fully explored using metallographic examination and numerical simulation. It is found cracks easily occur at their interface near nickel side due to alternate thermal cycles that lead to a variation in residual stress and microstructure, including grain orientation, texture strength, dislocation density and Schmid factors. The research outcomes enable better understanding of crack initiation mechanism in bimetallic structures printed by arc-based metal additive manufacturing and may advance the design and fabrication of advanced structures.