In-situ process monitoring and control of laser directed energy deposition using thermal imaging and computer vision

1. Abstract Laser direct energy deposition (LDED) is a prominent additive manufacturing (AM) technique due to its high deposition rates, scalability, and material efficiency. However, maintaining consistent part quality remains a significant challenge due to complex thermal cycles inherent to high-deposition processes, where rapid heat accumulation and varying cooling rates lead to heterogeneous microstructures and residual stress. This work introduces a data-driven in-situ process monitoring and control (ISPMC) framework for wire-fed LDED that combines high-speed infrared (IR) tomography, computer vision, and real-time process parameter adjustment to improve print quality. Here, high-speed infrared (IR) thermography was used to capture optical heat mapping and temperature history data, providing real-time insights into heat transfer and microstructural evolution. By integrating the IR data with computer vision, a predictive framework was developed for real-time adaptive control of LDED process parameters. Experimental validation demonstrated significant improvements in thermal stability, visual quality, and microstructural homogeneity across complex geometries. Optical microscopy revealed that No ISPMC samples developed dendritic and cellular grain structures, whereas ISPMC samples produced consistent equiaxed cellular grains throughout the build. Mechanical testing showed up to a 90% reduction in ductility variance and a 49% reduction in ultimate tensile strength variance compared to the No ISPMC samples. Nano-indentation further confirmed reduced hardness and modulus gradients throughout the build height, demonstrating improved thermal and mechanical homogeneity. These results establish ISPMC as an effective closed-loop control framework for reliable production of high-quality metal AM components.