• Nycz, Andrzej
• Roy, Sougata
• Silwal, Bishal
• Noakes, Mark
• Pudasaini, Niraj

Abstract

Wire Arc Additive Manufacturing (WAAM) is the process by which large, metallic structures are built, layer-by-layer, using a welding arc to melt wire feedstock. In this process, the proper se-lection of the shielding gas plays a vital role in depositing structurally-acceptable part geometries and achieving a quality surface finish. In this study, the authors used shielding gases consisting of a ternary mix (He, Ar and CO2) and a binary mix (Ar and CO2) to deposit wall geometries using an open loop-controlled WAAM system developed at Oak Ridge National Laboratory’s Manufac-turing Demonstration Facility. The binary blend produced a wider and shorter geometry, while the ternary blend resulted in a narrower build that was more equivalent to the CAD geometry. The data indicated that the binary blend gave a higher oxygen concentration in the weld as compared to that of the ternary blend. These infer the arc characteristics and heat input had a significantly higher impact on the weld penetration than the surface tension effect due to surface-active ele-ments. This is further verified by developing and applying a high fidelity computational fluid dynamics (CFD) model and the thermophysical properties of gas mixtures. The results from the model showed that, while the influence of increased oxygen concentration on the surface tension for the binary blend led to a deeper penetration, the ternary blend gave rise to heat flux to the workpiece.

Topics

• impedance spectroscopy
• surface
• Oxygen
• melt
• wire
• additive manufacturing
• collision-induced dissociation