In-situ temperature and emissivity monitoring of blue laser powder-blown directed energy deposition of copper

Additive manufacturing (AM) of copper is challenging due to its high thermal conductivity, low absorptivity under infrared lasers, and oxidation sensitivity. This study newly presents an integrated in-situ melt pool monitoring framework for blue laser powder-blown directed energy deposition (LP-DED) using multispectral imaging and photodiode sensing. Multispectral thermometry (MST) provides spatially resolved temperature and emissivity maps, while photodiode-based Planck thermometry (PDPT) enables high-speed radiance tracking. The measured thermal responses are highly sensitive to laser power and shielding conditions. The combined MST-PDPT analysis reveals how variations in emissivity affect temperature interpretation. The proposed multi-sensor approach establishes a foundation for reliable real-time thermal assessment and future closed-loop control of blue laser copper deposition.