In order to support a damage tolerant approach in the design of fatigue resistant Inconel 625 LPBF components, tensile specimens (ASTM E8) were manufactured in two build orientations (0 and 90o) and fatigue crack propagation specimens (ASTM E647) were manufactured in three build orientations (0, 45 and 90o), subjected to stress relieve annealing (870oC, 1h) and machined prior to testing. The absence of processing-induced defects, such as pores and inclusions greater than 25 um in size, was confirmed by the X-Ray microtomography analyses. The fatigue crack propagation behavior was evaluated for the cracks oriented parallel to build orientations of 0, 45 and 90o and perpendicular to a build orientation of 90o. During testing, the crack length was monitored via the compliance method and was validated with optical measurements. The static mechanical properties and the fatigue crack propagation behavior of a wrought alloy of the same composition were also studied for comparison.
It was found that following the stress relieve annealing, the static mechanical properties of the LPBF specimens were strongly anisotropic and differed significantly from those of their wrought counterparts. However, the difference in the fatigue crack propagation behavior of differently oriented specimens was much less pronounced. In the low stress intensity factor (SIF) range, the wrought specimens appeared to perform slightly better than the LPBF specimens, while in the high SIF range, the situation was reversed: the stress-relieved LPBF specimens perform better than their wrought counterparts.
Keywords: Additive manufacturing, Fatigue, Crack propagation, Damage tolerance, Laser Powder Bed fusion
- Visualize the build direction’s effect on the damage tolerance of anisotropic LPBF manufactured materials
- Compare the crack growth behavior of a wrought alloy and an LPBF manufactured Inconel