Effect of dwell time on fatigue properties of wire-arc additively manufactured IN718 alloy

Abstract

In this research, the effect of inter-layer dwell time and fabrication path strategy on fatigue properties of wire-arc additively manufactured (WAAM) IN718 alloy was studied. Three different dwell times i.e. 10 s, 50 s, and 90 s, and two path strategies i.e. uni-directional and bi-directional, were chosen. The results showed that the bi-directional fabrication strategy resulted in improved mechanical properties than the uni-directional one. Also, the quality of fabricated part i.e. the surface irregularities (roughness), geometrical accuracy, and porosities, was improved with an increase in the dwell times. The mechanical properties were improved as the dwell time increased from 10 s to 90 s: tensile strength by ∼ 18%, yield strength by ∼ 33 %, ductility by ∼ 20 %, and Hardness by ∼ 10%. The fatigue lives were high at higher dwell times and less scattered, owing to the smaller number of porosities. Fractographic investigation revealed either defect-free or defect-induced failures. The observed effect of dwell times and fabrication path strategy was accredited to the reduced heat accumulation, porosities, and residual stresses in the fabricated component at higher dwell times. The results supported by the formulated and validated numerical framework, have been argued in this study.