On the contribution of planned and unplanned build interrupts to the fatigue properties of Ti6Al4V from laser powder bed fusion

Abstract Additive manufacturing (AM) by Laser Powder Bed Fusion (L-PBF) offers several advantages over traditional methods in the manufacture of metal components. One concern in L-PBF is that interruptions to the build cycle could introduce defects within the component. Although the builds can often be resumed due to the layer-wise nature of the L-PBF process, the potential for defects and their contribution to component reliability are problematic and often require rigorous post-build inspections. The objective of this study was to characterize the metal obtained from builds of Ti6Al4V with interruptions and assess the fatigue behavior. The build interruptions included a planned pause and unplanned interrupt that resulted from recoater blade contact with the build. Results showed that there was no contribution from the build pause on the quality of metal or its fatigue properties. However, specimens that contained an unplanned interrupt exhibited a decrease in fatigue life compared to the control (i.e., without interrupt). Fractography revealed large (d > 200 μm) lack of fusion (LOF) defects near the unplanned interrupt that served as the failure origin in fatigue, but they were not identified in X-ray micro computed tomography (μCT) analysis. Numerous LOF defects developed at the unplanned interrupt layer line, which appears attributed to disruption of the powder layer and the preparations necessary for resuming the build cycle. Overall, results showed that unplanned build interrupts can reduce the fatigue strength of components produced by L-PBF and that post-build inspection by μCT may not be capable of identifying the detrimental defects produced.