Microstructural Evaluation of a Dissimilar Metal Interface of Ni-Co-Based Superalloys Fabricated Using Wire Arc-Directed Energy Deposition Additive Manufacturing.

Wire arc-directed energy deposition (WA-DED) is a promising additive manufacturing (AM) technique for building large, complex near-net-shape parts, combining high deposition rates and fully dense builds. The goal of this study was to explore the advantages of WA-DED for local property optimization by joining a high-strength nickel-based alloy with a wear-resistant cobalt-based alloy. Single-pass depositions of the IN718 Ni-based alloy on round L605 Co-based alloy stock were prepared, using a Fronius cold metal transfer (CMT) WA-DED system to achieve low heat input and clean weld passes. The influence of varying process control settings during the deposition process on the final porosity and interface integrity, as well as resultant variations in microstructure and mechanical property, were evaluated. The results indicate that the process did successfully produce crack-free, non-porous, and continuous welds. In the as-deposited condition, the weld metal showed the presence of Nb-enriched regions and phases, and variation in process control settings resulted in a change of mean precipitate size. The interface regions showed increases in hardness, likely due to precipitate strengthening during extended cooling times. Lastly, the general microstructure and mechanical properties showed relative insensitivity to changes in processing setting during WA-DED using the CMT system, allowing for greater flexibility during manufacturing. [ABSTRACT FROM AUTHOR]