Highly-efficient additive manufacturing of Inconel 625 thin wall using hot-wire laser metal deposition: Process optimization, microstructure, and mechanical properties

Hot-wire-based laser metal deposition (HW-LMD) technique was used for additive manufacturing of Inconel 625 thin-walled parts. The desired process window was obtained through the Taguchi experiment design, and the defect-free Inconel 625 thin-walled structures were efficiently manufactured with a wire deposition rate of 1.72 kg/h. The microstructure, phase composition, microhardness, and tensile properties of the Inconel 625 thin walls were studied in detail. The results showed that the microstructure of the Inconel 625 thin wall was mainly composed of a large number of columnar dendrites with an average grains size of 12.5 μm, and the growth direction of the columnar dendrites was perpendicular to the substrate surface. γ-Ni was the base phase of the as-deposited Inconel 625 thin walls and irregularly shaped Laves precipitates were observed in the inter-dendritic region. The microhardness of the Inconel 625 thin wall over the build direction was homogenous and the average microhardness was 258 HV1, which was 35.7 % higher than that of the wrought alloy. The tensile strength of the as-deposited Inconel 625 thin walls exhibited anisotropy according to the relationships between stress loading direction and microstructural texture. The maximum tensile strength and elongation of the as-deposited Inconel 625 thin wall were respectively 825.91 MPa and 55.62 %, which were close to the wrought alloy 625. Meanwhile, through comparative analysis, it was found that the tensile properties of the Inconel 625 samples fabricated in this study were superior to samples produced using conventional arc additive manufacturing methods.