Key Process Variable Tolerances and Their Impact on the Tensile and Fatigue Performance of Additively Manufactured Ti-6Al-4V

Deviations of key process variables (KPVs) in laser powder bed fusion machines, such as laser power, scan speed, and hatch distance, from their nominal values can occur due to the drifts in machine conditions over time. These small KPV drifts may lead to changes in part quality and their mechanical properties. In this study, the impact of process variations within the tolerance limits of an EOS M290 system was investigated by emulating the individual and combined effects of ± 4% drifts in laser power and ± 2.4% drifts in hatch distance on the defect-structure and mechanical properties, including tensile and fatigue. The results showed that the tensile behavior was not significantly impacted by the KPV drifts at their tolerance limits. However, minor variations in fatigue lives were observed due to KPV drift. Furthermore, the fatigue behavior was more affected by the part location on the build plate than KPV drift, as specimens at the center exhibited smaller crack initiating defects, and consequently, had longer fatigue lives than those away from the center.