Enhanced corrosion resistance at the heterogeneous LPBF SS316L-DED IN625 interface by different hybrid manufacturing strategies

Hybrid laser additive manufacturing, which combines laser powder bed fusion (LPBF) and direct energy deposition (DED), integrates the precision of LPBF with the flexibility of DED. While most studies have focused on mechanical performance, corrosion behavior at the interface has been rarely explored. This study investigates the corrosion behavior at the hybrid manufactured interface between LPBF stainless steel 316L (SS316L) and DED Inconel 625 (IN625) by comparing two interface transition strategies: direct transition (DT) and 50 %-50 % mixing transition (50/50). The interfacial microstructure, element distribution (particularly Nb), and passive film have been characterized to elucidate the corrosion behavior. Our results indicate that, compared to the 50/50 sample, Nb tends to accumulate at the DT interface predominantly in the form of solid solution and exhibits a lower tendency to precipitate as Nb-containing phases. This state enhances the diffusion tendency of Nb, raising its chemical potential and partially compensating for the activation energy required for further oxidation to Nb₂O₅ during anodic polarization under high voltage. Consequently, passive film integrity and secondary passivation behavior are improved, thus enhancing corrosion resistance of the hybrid-manufactured components. This work provides critical insights for optimizing corrosion resistance through tailored hybrid manufacturing strategies in advanced additive manufacturing systems.