Effect of Interlayer Machining Interventions on the Geometric and Mechanical Properties of Wire Arc Directed Energy Deposition Parts

Abstract

Wire arc directed energy deposition (Wire Arc DED) has become a popular metal additive manufacturing technique for its capability to print large metal parts at a high deposition rate while being economically efficient. However, the Wire Arc DED process exhibits geometric inaccuracies resulting from the variability in the bead geometry and demonstrates heterogeneity in microstructure and mechanical properties. This study investigates the use of tailored periodic machining interventions during the Wire Arc DED process to address these shortcomings. The as-built geometry and surface finish, microstructure, and microhardness of multilayer wall structures produced with and without machining interventions carried out at different temperatures are compared. The machining interventions are found to reduce the uncertainty in bead geometry evolution and significantly improve the surface roughness of the as-built walls, thus reducing the need for further postprocessing of the wall surfaces. Although the microstructure constituents of the as-built wall structures with and without machining interventions are similar, the machining interventions result in finer grains in the interior of the part. Machining interventions are found to yield a statistically significant increase in microhardness, indicating increased strength compared to Wire Arc DED alone. In addition, the spread of the microhardness distribution is reduced in Hybrid Wire Arc DED, indicating improved homogeneity of the grain size distribution compared to Wire Arc DED alone. The study shows that the proposed hybrid manufacturing technique has the potential to control and improve the geometric and mechanical properties of additively manufactured metal components.