A study on the effect of shielding gases on the GMAW-WAAM process and performance of WAAM-deposited low-carbon steel

Wire Arc Additive Manufacturing (WAAM) is a direct energy deposition-based additive manufacturing process that uses an arc welding power source to fabricate large-scale 3D components from wire feedstock. In order to optimize the WAAM process, it is crucial to understand how process variables, such as shielding gas composition, affect build quality. This study investigates the effects of pure Ar, pure CO 2 , and Ar+CO 2 (80:20) shielding gases on single- and multi-layer depositions using a six-axis robotic WAAM system equipped with an automated wire feeder. The objective is to evaluate how these gases influence the bead profile, microstructure, and mechanical properties of WAAM-deposited low-carbon steel. Results show that Ar+CO 2 shielding yields the widest bead profiles with a uniform surface finish, while CO 2 shielding enhances penetration but results in coarser microstructures and lower alloy retention. Ar shielding produces finer grains and the highest hardness, while tensile strength remains comparable under Ar and Ar+CO 2 , with the latter providing higher elongation. Charpy impact tests reveal that Ar-shielded builds have the highest toughness, CO 2 -shielded ones the lowest with brittle features, and Ar+CO 2 -shielded builds exhibit toughness and fracture behavior similar to those under Ar shielding. These findings provide valuable insights for selecting shielding gases to tailor the geometric and mechanical performance of WAAM builds.