Application of hot wire laser directed energy deposition for efficient fabrication of large nickel-based alloy components: Process, microstructure, and mechanical properties

Enhancing the wire deposition rate while ensuring deposition stability is a critical challenge in fabricating large nickel-based alloy components using hot wire laser directed energy deposition (HW-LDED) technology. In this study, a preheating mathematical model for Inconel 718 wire was initially established and experimentally validated. Subsequently, based on the optimal matching between the wire feeding speed and preheating current, Inconel 718 components were efficiently fabricated with a wire deposition rate of 3.1 kg/h. Ultimately, the microstructure evolution, phase composition, and mechanical properties of the HW-LDED Inconel 718 samples were comprehensively investigated. The results revealed that the microstructure of the HW-LDED Inconel 718 samples consisted of columnar dendrites exhibiting a pronounced {100} < 001 > texture, with an average grain size of 16 μm. The primary phase in the HW-LDED Inconel 718 samples was the γ-Ni phase, accompanied by Laves and carbides in intergranular regions. The average hardness of the HW-LDED Inconel 718 samples was 253.5 HV1.0. The tensile strength and elongation were 1112.1 MPa and 36.13 %, respectively, while the impact absorbing energy reached 85.97 J. The tensile and impact fracture surfaces displayed numerous dimples, indicative of ductile fracture behavior of the alloy under applied loading. The Laves phase facilitated the initiation and propagation of cracks during the alloy's deformation process, with elongated Laves phases undergoing fragmentation and smaller Laves phases experiencing debonding from the matrix. This research presents a viable solution for the efficient fabrication of large nickel-based alloy components. Furthermore, the findings offer valuable insights into the interrelationships among the deposition process, microstructure, and properties of the HW-LDED Inconel 718 alloy.