The process study and parameter influence in Wire Arc Additive Manufacturing (WAAM) of titanium using hot-wire plasma arc welding

Abstract

This research aims to study and develop the Wire Arc Additive Manufacturing (WAAM) process for titanium alloys utilizing the Hot-Wire Plasma Arc Welding (Hot-Wire PAW) technique. Due to titanium’s high susceptibility to oxidation during melting, a specialized inert gas shielding device was designed. Process optimization was subsequently conducted using a Full Factorial Design of Experiment (DOE) via Minitab software to determine the optimal parameters: a welding speed of 1.83 mm/s, a wire current of 35 A, and a wire feed rate of 0.85 m/min. Microstructural analysis utilizing the EDS technique confirmed the purity of the deposited titanium, indicating zero oxygen contamination. Furthermore, 3D microscopy revealed grain structure variations induced by the repeated thermal cycles inherent to the layer-by-layer deposition process. In-depth mechanical testing also exposed anisotropic behavior; specifically, tensile strength and ductility differed between the vertical and horizontal build directions, with horizontal specimens achieving an Ultimate Tensile Strength (UTS) of 560.80–693.58 MPa, compared to 631.65–677.10 MPa for vertical specimens. Additionally, Vickers hardness values ranged from 199.8 HV to 266.8 HV, demonstrating a decreasing trend along the height of the specimen. The findings of this study establish a crucial foundation for the cost-effective production of high-quality, large-scale titanium components for advanced industrial applications.