Insights into Fatigue Damage in Additive Manufacturing through Process-Structure-Property Interactions

Additive manufacturing (AM) has transformed modern production by enabling complex geometries, reducing material waste, and shortening lead times. Yet, a central challenge in metal AM remains ensuring structural integrity and long-term performance under cyclic and monotonic loads, given the process-induced defects and heterogeneous microstructures inherent to layer-wise fabrication. Among metal AM routes, selective laser melting (SLM), a powder bed fusion process, dominates high-performance applications and presents distinctive damage-tolerance challenges arising from rapid thermal cycling and defect sensitivity. This review critically examines how SLM process parameters govern defect formation, microstructure evolution, and the resulting fatigue and fracture responses under mechanical loading. Particular emphasis is placed on the interplay among processing conditions, melt-pool dynamics, microstructural gradients, and property anisotropy. The role of gradient structures in crack initiation and propagation is assessed, highlighting mechanisms that control small-crack growth and thresholds. By synthesizing current evidence and exposing gaps, especially in quantitative links from process parameters to damage tolerance, this review provides guidance for designing more reliable, durable metal components manufactured via SLM.