Plasma behavior and control with small diameter assisting gas nozzle during CO2 laser welding

The laser-induced plasma is an important physical phenomenon during the process of penetration welding with high-power CO2 laser. To study the effect of assisting gas in the laser-induced plasma behavior and characteristics of weld formation, different configurations of heat input and side assisting gas were arranged to investigate the plasma behavior, and plasma images were recorded using high speed camera. By analyzing plasma images, spectrum intensity, and static pressure, the results have showed that the application of side assisting gas suppresses the laser-induced plasma significantly and improves the utilization of laser power, in which a sound weld quality is obtained. The combination of side nozzle used in the study with a gas flow rate around 20 L/min, the mixed gas composed of helium and argon in which helium accounted for 75%, and the position of side nozzle in which x and y were set at around 0 mm, h was set at around 6 mm could bring good controlling effect on plasma and well weld seam profile as well as deeper penetration. The reference value provides a promising solution to improve the absorption and efficiency of laser power during CO2 laser welding using side assisting gas.