Recyclability in Metal Additive Manufacturing: Bridging Powder Lifecycle, Defect Evolution and Fatigue-Critical Reliability Across SLM and EBM

Powder recyclability in metal additive manufacturing has become a critical requirement for improving sustainability, cost-efficiency, and industrial scalability, particularly in powder bed fusion processes such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM). Despite growing interest in powder reuse, the available literature remains fragmented, often addressing powder degradation, process defects, or mechanical performance as isolated topics. This separation limits understanding of how powder lifecycle evolution affects fatigue-critical reliability, where small variations in powder condition may strongly influence long-term structural integrity. This review aims to establish a unified process–structure–performance perspective linking powder reuse, degradation mechanisms, defect evolution, and mechanical reliability in SLM and EBM. A structured literature analysis was conducted to examine changes in powder morphology, particle size distribution, chemical composition, oxygen uptake, moisture interaction, flowability, and thermal history across reuse cycles. Attention was given to the relationship between powder degradation mechanisms and defect formation during processing. The review shows that static mechanical properties, including tensile strength and hardness, may remain comparatively stable after multiple reuse cycles. In contrast, fatigue performance is markedly more sensitive to powder condition, owing to the accumulation of defects such as oxide inclusions, porosity, lack-of-fusion regions, and irregular melt-pool features. Distinct degradation pathways were identified: SLM is mainly governed by oxidation-related effects, whereas EBM is more strongly influenced by particle coarsening, morphology changes, and thermal exposure. Powder recyclability should be considered not only as a sustainability issue but also as a reliability-driven engineering challenge. The proposed framework supports reuse decisions by integrating powder lifecycle assessment with defect tolerance and fatigue-critical performance requirements.