Plasma Plume Effect in Laser Welding under Subatmospheric Pressure

In laser welding, the plasma plume often shields the input energy, causing laser beam defocusing and significantly impacting welding efficiency and quality. This paper elucidates experimental facts concerning the attenuation and dispersion of laser energy at varying ambient pressures, and derives the associated absorption and refraction mechanisms of the plasma plume. By analyzing experimental and simulation results from scholars, the mechanism by which laser-plasma interaction affects weld formation is illustrated. A comprehensive analysis is conducted on the impact of ambient pressure and welding speed on weld morphology. The conclusion drawn is that there is a good correspondence between the influence of ambient pressure on melting depth and plasma plume, with a material-dependent critical pressure value. Furthermore, higher welding speeds decouple ambient pressure from weld depth but contribute to reducing porosity defects. Therefore, appropriate welding speeds and ambient pressures should be selected based on actual industrial application scenarios. Finally, the paper suggests future research on LWSP should focus on real-time monitoring with multi-sensor fusion, optimizing machine learning models, exploring novel imaging techniques, and combining LWSP with hybrid welding.