Effect of defects and a build pause on fatigue life of additively manufactured 316L stainless steel

Abstract

Build pauses can occur during metal additive manufacturing (AM) with laser beam powder bed fusion (PBF-LB) for a variety of reasons such as power outage, insufficient gas flow, or sensor failure. It is economically desirable to continue a build after the issue is resolved. The effect on part quality, namely microstructure, surface roughness, geometric features, and the impact on the fatigue performance is not well understood. This study considers parts fabricated with a 2-hour build pause in the center of the gauge section. Comparisons of the dimensions, as-printed surface features, microstructure, and fatigue performance are determined. Geometric deviation from part shift during the build pause is significant, however other flaws inherent to AM can also dominate failure depending on severity. A stress intensity factor approach is utilized to determine the influence that the geometric variation and the individual flaws had on the fatigue life. A model is developed to predict and determine part performance after a build pause. Understanding the effect of mechanical changes and geometric shifts from a build pause can help reduce scrap from unintended build interruptions.