A critical review of laser wire directed energy deposition: Toward large-scale metal additive manufacturing

The future of additive manufacturing (AM) is evolving beyond small-scale prototyping toward the production of large-scale, high-performance, and high-value metal components. Laser wire directed energy deposition (LW-DED) has emerged as a promising AM technology in this scenario, offering meter-scale builds, kilogram-per-hour productivity, near-zero material waste, and laser-based precision, with research activity having grown tenfold in the past few years. This comprehensive state-of-the-art review integrates the fragmented knowledge landscape of LW-DED, covering its historical evolution, process fundamentals, machine architectures, material–process–structure–property relationships, multi-physics modelling, sustainability and techno-economic considerations, and AI-driven in-situ monitoring, supporting the transition toward fully autonomous digital manufacturing. We critically assess demonstrated applications, ranging from titanium structures to tungsten components for fusion reactors, distinguishing between optimistic expectations and genuine industrial value. This work provides a framework for positioning LW-DED within the broader landscape of large-scale metal additive manufacturing, and identifies key unresolved challenges to outline a research roadmap for industrial deployment.