Control of the melt pool size is necessary to achieve more homogenous material properties in wire arc additive manufacturing (WAAM). The melt pool size can be measured by camera imaging or temperature field measurement. The paper aims to investigate the feasibility of using a high dynamic range two-colored pyrometric camera (Pyrocam) for melt pool size measurement in a gas metal arc welding-based WAAM process. A set of band-pass filters is identified using spectroscopy analysis to reduce the optical arc emission while the melt pool remains visible. The fusion line is identified in temperature field images, the melt pool size is measured by an automated algorithm, and the results are compared with high-speed camera images. A possible correlation between melt pool size and the grain size is examined.

Wire arc additive manufacturing (WAAM) of titanium parts shows promising potential for aerospace application due to its high deposition rates allowing a fast and economical production of large integral parts. However, due to the demands of aerospace industry an extensive qualification procedure is necessary to enable the parts as ready to fly. Nowadays, qualification for additive manufactured parts is a time-consuming process, so the advantages in additive manufacturing cannot be fully utilized. For this reason, a complete process qualification for WAAM would reduce the costs drastically in contrast to qualifying manufactured parts individually. As a first step the robustness and reproducibility of the energy reduced WAAM process was investigated. Thick-walled samples are manufactured layer by layer with an oscillating welding head motion. The mechanical properties of the samples are compared on an adequate statistical basis. Microstructural-and computer tomography analysis are conducted to comprehend shown interactions. The reproducibility is investigated in dependence of different heat treatment states, different directions of mechanical testing and two manufacturing systems of the same type.

Wire arc additive manufacturing (WAAM) of titanium parts shows promising potential for aerospace application due to its high deposition rates allowing a fast and economical production of large components. The cost savings are high, especially for expensive alloys like Ti-6Al-4V. However, due to high oxygen affinity of Ti-6Al-4V at elevated temperatures an excellent shielding gas coverage seems necessary to prevent embrittlement of the material during the welding process. Regarding the future development of local shielding gas coverage set-ups for gas metal arc welding (GMAW) based WAAM, this study investigates the influence of the oxygen content in the shielding gas chamber on mechanical properties of Ti-6Al-4V during the welding process. Samples are welded at different oxygen contents in the shielding gas chamber and stress-relief heat treated afterwards. Inert gas milling and hot gas extraction are used to determine the material oxygen content at different deposition heights. Metallographic methods are used to show macroscopic grain structure, evaluate possible α-case thickness and its dissolution by the subsequent layer. Hardness testing is used to investigate possible material inhomogeneities in the deposit and tensile properties of the material welded at different chamber oxygen contents are displayed. It is concluded, that even at high chamber oxygen levels of 6000 ppm the welding process is stable, the forming α-case at top of the layer dissolves in the melt pool of the subsequent layer and that the aerospace requirements on tensile properties can be reached.

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