Arc-based directed energy deposition of novel high-strength steel: Study on process parameters, microstructure and mechanical properties

High-strength steels (HSS) are widely employed in aerospace, transportation, and energy industries owing to their exceptional strength-to-weight ratio. Traditional manufacturing methods struggle to meet the demands of complex geometries and large-scale HSS components due to limitations in material utilization, cost, and production time. Arc-based directed energy deposition (DED-Arc) emerges as a promising solution, yet its success hinges on precise optimization of process parameters. This study systematically investigates the effect of thermal input and arc oscillation parameters on the deposition quality, microstructure, and mechanical properties of DED-Arc-processed HSS. Results indicate that heat input significantly influences the melt depth, width, and height of the weld bead. Specifically, increasing heat input generally increases molten pool volume and depth, while lower heat input may restrict metal flow, causing irregular weld bead shapes or insufficient fusion. Better bead morphology was observed at 7.5 mm/s travel speed. Notably, an increase in arc oscillation width resulted in wider and shallower weld beads with reduced height. A swing width of 4 mm yielded well-shaped deposits with a higher material utilization rate of 69.8 %. The deposited workpiece's microstructure mainly contains martensite and a small amount of austenite, with local variations in structure across regions due to heat accumulation. Electron backscatter diffraction (EBSD) results showed an average grain size of 23.92 ± 5.75 μm, 29.4 % high-angle grain boundaries (HAGBs), 6.8 % austenite content, and a geometrically necessary dislocation (GND) density of 4.83 × 10¹⁴ m⁻². Mechanical properties were favorable, with an average Vickers hardness of 354.68 HV, average ultimate tensile strength of 1112.0 MPa, average yield strength of 719.5 MPa, and average elongation of 20.3 %. This study provides a theoretical basis for optimizing the DED-Arc process for novel low-cost HSS.