Bonding SS316L and IN625 through laser powder bed fusion and directed energy deposition: a comparative tensile analysis

Directed Energy Deposition (DED) was used to deposit Inconel 625 (IN625) onto 316L stainless steel (SS316L) substrates fabricated by Laser Powder Bed Fusion. Tensile properties of the resulting multi-material specimens were compared to those of the individual alloys. Two bonding approaches were evaluated: a direct transition and a 50/50 intermediate layer formed by blending equal parts of each alloy during deposition. The multi-material specimens demonstrated higher yield strength than the single alloys. However, samples with the 50/50 transition exhibited brittle failure at the joint, whereas the direct transition behaved more ductile. Scanning Electron Microscopy revealed microcracks at the interface of the 50/50 transition, and Energy Dispersive Spectroscopy detected aluminum oxide particles in the DED-IN625 samples. These results underscore the importance of transition design in multi-material components and provide guidance for optimizing mechanical performance in demanding applications such as in extreme conditions, particularly where structural integrity and high-performance bonding are critical.