Research on a Low-Cost, Low-Waste Method for Surface Flatness Improvement of WAAM Components Based on Tungsten Inert Gas Arc Remelting (TIGAR)

Wire-arc additive manufacturing (WAAM) has fully empowered the design and manufacturing of metals with its unparalleled efficiency and flexibility. However, the process has relatively poor shape control capabilities, often requiring machining post-processing. This study explores a tungsten inert gas arc remelting (TIGAR) process to improve the surface flatness of WAAM components at a low cost and significantly reduce machining waste (up to 76%), which is crucial for the sustainable development of the process. The extent of surface improvement under different remelting currents was investigated. A detailed discussion was held on the mechanism by which the remelting arc, along with its molten pool, improves surface flatness. The robustness and adaptability of the process in a rough production environment were examined. And the impact of the process on the microstructure and hardness of the additive part's surface was examined. Through systematic and quantitative analysis, it was found that within a certain range, the improvement effect on flatness increases with the increase in remelting current; when the remelting current reaches 80 A, it can significantly reduce the maximum height difference (65%) and the standard deviation of surface height (66%), and the remelting effect is uniform and reliable. TIGAR has a flattening effect on both the protrusions and depressions of the additive part's surface. Proper overlap of remelted passes is crucial for the improvement of surface flatness. If the spacing of remelted passes is changed or the direction of remelting is adjusted, it is necessary to ensure the width of the molten pool to achieve sufficient overlap between adjacent remelted passes.