High-quality forming of laser DED components based on a multi-source sensing system

Laser directed energy deposition (LDED) is an additive manufacturing technology that uses a laser as the energy source to create a liquid melt pool in the deposition area, which rapidly moves it, melting powder and depositing layers sequentially. Given that the LDED process involves intense energy exchange and complex physicochemical changes, the quality control of the formed parts and the repeatability of the process are common technical challenges for its large-scale application. This paper establishes an integrated in situ monitoring system for LDED, which can monitor the geometric characteristics of the liquid melt pool, temperature, and high-temperature strain on the side walls of the formed parts, through a temperature sensing unit, a visual sensing unit, and a strain unit based on digital image correlation algorithm. Based on the information obtained from multi-source sensing of the cladding process, we compared the stability and forming quality of the cladding process under different process parameter paths and identified a process path that yields more stable melt pool temperatures, reduced fluctuations in melt pool dimensions, and lower peak strains on the build sidewalls; the maximum strain eyy and exx were 23% and 20% lower; and the strain fluctuation range of eyy and exx was found to be 45.65% and 26.49% lower compared to components built before process optimization, thereby achieving high-quality construction manufacturing when building cladding components of the same size.