Effective monitoring of laser welding (LW) processes is crucial for ensuring consistent, high-quality welds. Traditional monitoring techniques, such as thermal imaging, vision systems, acoustic emissions, and optical signal analysis, offer insights into weld pool dimensions, keyhole stability, and vapor plume behavior. However, these methods often lack the temporal and spatial resolution necessary for comprehensive analysis.

This study introduces the application of transverse heat flux sensors (THFS), leveraging the transverse Seebeck effect to achieve nanosecond response times. Building upon our preliminary research, we have incorporated specialized optical filters to effectively isolate laser radiation from the reflected thermal emissions of the workpiece, enabling precise quantification of reflected energy.

Experiments were conducted on various metals with differing thicknesses under a range of laser power settings. The THFS were strategically positioned to capture the three-dimensional distribution of heat flux during LW. Our findings reveal distinct correlations between heat flux signatures and keyhole dynamics, as well as melt pool flow characteristics. Notably, in conduction mode at 1 kW, the vertical heat flux was observed to be twice as high as in keyhole mode at 10 kW, with a standard deviation over three times greater.

Furthermore, the study explores the potential of modulating laser power during welding to enhance weld quality. The insights gained underscore the applicability of heat flux sensing methodologies not only in LW but also in processes like Laser Powder Bed Fusion (LPBF), offering a pathway (including AI post-processing algorithms) to improved thermal management and process optimization in laser-based manufacturing.