Effect of Repeated Powder Reuse on the Quality and Mechanical Properties of Ti-6Al-4V Fabricated by Laser Powder Bed Fusion

This study evaluated the effect of repeated powder reuse on the quality and mechanical properties of Ti-6Al-4V fabricated by laser powder bed fusion. Gas-atomized Ti-6Al-4V powder was repeatedly reused up to 15 build cycles, and changes in powder morphology, oxygen content, hardness, tensile properties, microstructure, and localized inclusions were examined. Repeated reuse progressively degraded the initially spherical powder morphology, as evidenced by the increased presence of satellite particles, irregular particles, and partially melted particles. The hardness of the fabricated specimens increased from approximately 375 HV in the virgin powder condition to approximately 411 HV after 15 reuse cycles. In contrast, the ultimate tensile strength and yield strength showed only limited variation, whereas elongation decreased from 10.7% to 7.4%. Optical microstructural observation revealed no significant change in the overall acicular α/α′-dominated microstructure, indicating that the ductility reduction could not be explained solely by microstructural variation. Oxygen content gradually increased with reuse cycles and exceeded the ASTM F2924 limit after more than six reuse cycles. In addition, SEM-EDS analysis of the specimen fabricated using powder reused for 15 cycles revealed a localized inclusion-like region enriched in O, C, and Si. Based on oxygen specification compliance, ductility retention, localized inclusion formation, and cumulative raw powder cost reduction, powder reuse up to six cycles was proposed as a practical reuse limit under the present LPBF conditions.