Fabrication of Custom Alloy Wire Feedstock for Large Area Directed Energy Deposition

Directed Energy Deposition (DED) is an emerging additive manufacturing technology gaining attention for its capability to print large structures. Currently, it is difficult to procure custom alloy compositions of wire to serve as feedstock for these arc- or laser-based robotic deposition systems. To support development efforts, research teams are typically constrained to traditional welding wire, wire that is only available in large batches, or wire with chemistry limitations lacking the necessary elements for optimal deposition. This presentation will describe the process for fabricating custom composition alloys to serve as feedstock for U.S. Army Research Laboratory research on large area DED technology. Custom compositions of a Cupronickel wire were fabricated in a small batch manufacturing cell that was comprised of a directional solidification induction melting operation, induction heating for hot wire pressing, intermediate annealing, and successive cold wire drawing operations to reduce as cast 6 mm alloy rods to desired 1.15 mm DED wire feedstock. Custom alloy compositions can be melted in the caster to produce 6 mm round rods which are rolled down to 1.5 mm square in the hot press. After softening using annealing, the cold drawing operation is then used to take the wire from 1.5 mm square to 1.15 mm round. Produced wire was intermittently characterized using digital microscopy between drawing steps. Additional surface characterization was employed using scanning electron microscopy on samples of increased interest. A continuous quality control capability was added to provide a digital twin of wire quality on concentricity and connectiveness. Each run of the process produces approximately 10 lb. of wire feedstock. The presentation will describe the process, surface defects that may occur, defect mitigation techniques, expansion to Stellite and MAR250 alloys, and scaling of the process to provide wire batches from 5 to 25 to 100 lbs.