Role of side assisting gas on plasma and energy transmission during CO2 laser welding

In this paper, the effect of how the side assisting gas influences the laser-induced plasma and energy transmission in CO2 laser welding is studied. Under different configurations of the side assisting gas, the optical emission and spectrum signals from the laser-induced plasma were obtained and compared. From signal analysis and evaluation of weld results, it shows that the application of side assisting gas greatly suppresses the laser-induced plasma and enhances the efficiency of laser energy transmission, which in turn results in a sound weld quality with full penetration. A physical model of plasma consisting of diffusive plasma and residual plasma was also proposed and validated to illustrate the role of side assisting gas. The results suggest that the diffusive plasma can be blown away by the side assisting gas. This observation provides a promising solution to increase the absorption rate and utilization efficiency of the laser energy during laser welding by diminishing the diffusive plasma through side assisting gas. (C) 2010 Elsevier B.V. All rights reserved.