Feasibility study of WAAM application on superalloy Inconel 718 in aerospace industry – impact of shielding gas

This study examines the application of Cold Metal Transfer Wire Arc Additive Manufacturing (CMT-WAAM) to Inconel 718. Seven shielding gas combinations were assessed by depositing multi-bead (‘snicker’) samples. The samples were characterized with respect to defect occurrence, penetration depth, bead geometry (width, height and toe angle) and arc power. The results confirm the high feasibility of using WAAM for Inconel 718. Among the tested gases, the gas mixture of 2% H2 in Ar (sample R7) exhibited no crack-like defects, minimal volumetric defects, a larger toe angle and a higher width-to-height (W/H) ratio, while maintaining reduced penetration compared to the other gas combinations. Shielding gas composition was found to significantly influence arc power at constant wire feed speed, with a strong correlation to carbon dioxide (CO2) content. Elevated arc power, in turn, was associated with increased defect formation, particularly crack-like defects. A strong correlation between toe angle and W/H ratio was also observed, both being sensitive to shielding gas composition. Moreover, shielding gas selection substantially impacted the overall geometry of the deposited structures.