EVALUATION OF THE PROCESS PARAMETER AND PERFORMANCE OF L-DED SS316L-IN718 BIMETALLIC STRUCTURES

Laser Direct Energy Deposition (L-DED) is a promising additive manufacturing technique with potential application in joining two dissimilar materials to fabricate bi-metallic components. The quality and functionality of the bonding interfaces are of great significance and rely heavily on the process parameters. In this work, we first deposited IN718 on a wrought SS316L substrate to create a bimetallic interface. Different energy density values, ranging from 71.43 to 127.7 J/mm, were used through various combinations of laser power and scanning speed for deposition. The bimetallic interface quality in terms of interface geometry, morphology, and dilution values was investigated for every energy density. Geometric analyses and dilution measurements revealed that the optimum bimetallic fabrication was achieved with an energy density of 90–100 J/mm. To deposit bimetallic SS316L-IN718 blocks for mechanical testing, the laser power and scan speed were set to 1400 W and 14 mm/s, respectively. Line EDS measurements revealed a transition zone across the bimetallic interface within a 4 mm distance, avoiding abrupt chemical discontinuities. Micro-hardness testing using Vickers revealed a smooth hardness transition between the SS316L (~210 HV) and IN718 (~300 HV) sides without any defect formation, suggesting successful joining. The bimetallic structure exhibited yield strength of 268.88 ± 20 MPa, tensile strength of 462 ± 12 MPa, and elongation of 19.6 ± 0.8%, in good agreement with SS316L. The fracture occurred on the SS316L side with noticeable necking and ductile behavior, demonstrating good interfacial bonding. These findings demonstrate the potential of L-DED in the fabrication of bimetallic structures for structural applications.