This paper aims to investigate the effect of rolling force on the fatigue properties of Inconel 718 with hybrid wire arc additively manufacture (WAAM) and cold rolling. The relationship between the fatigue life and the grain morphology and precipitates needs to be analyzed.
Thin-walled Inconel 718 samples were prepared by hybrid WAAM and cold rolling process with different rolling forces. Low-cycle fatigue tests at room temperature were conducted for measurement of fatigue life. The grain morphology, precipitates and tensile properties before and after heat treatment were investigated.
The fatigue life decreases with the increased rolling force without heat treatment; while the increased rolling force enhances fatigue life after heat treatment. The columnar dendrites with average arm spacing of 85 µm change to equiaxed grains with size of 15.2 µm with the rolling force of 75 kN, meanwhile, the islands of Laves phase are fragmentated into discrete small pieces after the rolling process. The cold-rolled samples show fatigue hardening during the cyclic loading, while the as-deposited one only shows softening after heat treatment.
This study provides a hybrid method to improve the fatigue properties of WAAM deposited Inconel 718. The mechanism of fatigue hardening and softening is revealed, which is related to the stress level and its interaction with the Laves phase.
