Effect of Shielding Gas on the Penetration and Mechanical Properties of a GH3535 Alloy Fabricated by Wire Arc Additive Manufacturing

It is susceptible to lack of fusion because of shallow penetration when Gas Tungsten arc welding-based wire arc additive manufacturing is applied to the GH3535 alloy, thereby reducing its mechanical properties. The mixed shielding gas has great potential to improve penetration depth. The results show that the penetration depth can increase by 40.1% and 21% with the addition of 5% hydrogen gas (H₂) and 50% helium gas (He), respectively, to the pure Ar shielding gas. Both hydrogen and helium can improve the heat input, thereby increasing the penetration depth. However, compared with helium, hydrogen can greatly promote the arc contraction and increase the energy density, thus improving the penetration depth. Therefore, hydrogen can improve penetration more significantly. The microstructure of thin-wall samples fabricated by wire arc additive manufacturing is dominated by coarse columnar dendrites, and there are both eutectic M₆C carbides and nano-scale M₂C carbides. The addition of hydrogen slightly reduces the yield strength and ultimate tensile strength of the thin-walled sample and slightly increases the elongation. However, the addition of helium has no significant effect on the tensile properties of thin-walled samples.