Energy modeling and process mapping for defect-free hot-wire laser deposition of Inconel 718 single beads

Hot-wire laser additive manufacturing (DED-LHW) addresses key limitations of conventional cold-wire processes, where excessive laser energy overheats the melt pool and promotes columnar grain growth, degrading microstructural properties. In addition, a large fraction of the laser power is lost by reflection at the metallic surface, resulting in low overall energy efficiency. DED-LHW introduces electrical current for resistive wire preheating via the Joule effect, complementing laser energy to reduce required laser power and enhance deposition stability. This study develops a critical energy delivery model that quantifies the linear thermal energy supplied to the wire by both laser in a three-beam coaxial configuration and Joule heating. The model precisely predicts and prevents dripping and stubbing defects, as validated experimentally through comprehensive process mapping for Inconel 718. The effects of laser power, current, scanning speed, and wire feeding speed on bead morphology and dilution are extensively investigated. Results confirm that the laser must provide at least half of the total wire energy for optimal stability, with Joule heating as a complementary source. DED-LHW achieves twice the deposition rate at 50% laser power compared to cold-wire deposition, producing smoother beads, more refined contact angle control, and a finer microstructure. This directly reduces energy consumption and production time while eliminating defects.