Recent progress in surface post-treatment techniques for additive manufactured alloy metal parts: A comprehensive review

Metal additive manufacturing has emerged as a transformative approach in advanced manufacturing, playing an increasingly pivotal role in the aerospace, automotive, medical, and electronics industries. However, the layer-by-layer deposition process inherently introduces surface defects, microstructural inhomogeneity, and residual stresses, which cannot be fully mitigated during fabrication and severely compromise the mechanical performance and fatigue reliability of the final product. Consequently, post-processing technologies have become a decisive enabler for industrial adoption, serving as a critical step to regulate surface integrity and service performance. This article provides a comprehensive review of the historical evolution and recent progress in metal AM post-processing techniques. A classification system is proposed based on material removal mechanisms in which these techniques are classified as contact- and non-contact-based approaches. Subsequent subdivisions are established based on the nature of the contact forces and energy sources. This review highlights the mechanistic principles that govern surface topography reconstruction, subsurface microstructural evolution, and performance enhancement in terms of fatigue or wear resistance. In addition, it summarizes notable advancements in each domain. Three cutting-edge research frontiers are identified, including the synergistic effects of hybrid multi-energy field post-processing, the challenges in adapting post-processing for novel AM alloys, and cross-disciplinary simulation-driven process optimization. Finally, future perspectives are presented, emphasizing the transition toward standardized, intelligent, green, and precision-oriented post-processing and the need for industry-wide benchmarks, digital twin-integrated technologies, and eco-friendly surface engineering strategies. Thus, the present work provides a theoretical framework and technical roadmap for the advancement of metal AM post-processing and the development of integrated AM post-processing systems.