Defect Formation, Detection, and Quality Assurance in Additive Manufacturing: A Systematic Review

Additive manufacturing (AM) enables the production of geometrically complex components but introduces process-dependent defects that may compromise dimensional accuracy, surface integrity and mechanical reliability. This systematic review examines defect formation, defect-sensitive quality phenomena, detection and quality assurance across the principal AM process categories, distinguishing discrete manufacturing discontinuities from geometrical deviations, surface-quality attributes and process-dependent material responses. Literature published between 2010 and 2025 was retrieved through CrossRef and screened using a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-informed procedure, resulting in 134 publications included in the final analytical corpus. The synthesis shows that defect formation is governed by interacting material, process and thermal-history variables and that apparently similar defect manifestations can arise from substantially different mechanisms across AM processes. Inspection capability is likewise process- and defect-dependent: X-ray computed tomography (XCT), including micro-computed tomography (µCT), is particularly suited to internal volumetric discontinuities, whereas optical and three-dimensional scanning primarily address external geometry and surface conformity. The principal contribution of the review is an integrated process–material response–quality manifestation–performance–inspection–qualification framework that connects process-dependent defect and quality formation with engineering consequences, inspection capability, quality-assurance decision-making and industrial qualification.