Many studies have been conducted to evaluate the mechanical properties of laminations by wire arc additive manufacturing (WAAM), However, these studies do not guarantee that the moldability of laminations during industrial applications is taken into account. Especially when fabricating complex shapes such as turbomachinery impeller blades, heat input from arc welding can cause defects in the lamination process, so it would be industrially useful to clarify the mechanical properties under conditions where formability is guaranteed. Therefore, in this study, the mechanical properties of WAAM laminations were evaluated under conditions in which axial-flow impellers can be fabricated by WAAM and machining. In particular, since WAAM can improve the fabrication process of difficult-to-machine materials, Inconel 718, a typical difficult-to-machine material, was targeted in this study. In addition, the shape of the axial-flow impeller was based on the fan type inducer developed in a previous study [1], and the blade shape was designed as a DAE airfoil shape to study complex shapes. For the purpose of upgrading the manufacturing of the impeller, a multi-material impeller was designed with Inconel 718 for the blade and JIS SUS304 for the hub.

Result of tensile test, tensile strength: 786 MPa, 0.2% proof strength: 541 MPa and elongation: 35% were obtained as the average values from 3 tests. Compared to the results of butt-welded joints of Inconel 718 without heat treatment performed by Sonar et al. under room temperature conditions [2], the tensile strength was approx. 80 MPa lower, the 0.2% proof strength was similar and the elongation was approx. 7 points higher.This difference can be attributed to the different welding / WAAM conditions.

[1] S. Ejiri International Journal of Fluid Machinery and Systems, 2023, 16-2, pp.184-191.

[2] T. Sonar, et. al, Materials Characterization, 2021, 174, 110997.