Effects of gas shielding parameters on weld penetration of CO2 laser-TIG hybrid welding

Shielding gas is the crucial reason for the process stability and the efficient synergetic effects between the laser and arc of CO2 laser-tungsten inert gas (TIG) hybrid welding, resulting in deeper weld penetration depth. However, there have been few systemic reports about this experimental phenomenon. Then, a detailed experiment of CO2 laser-TIG hybrid welding with different shielding gas methods, is carried out on the 316L stainless plate. The results demonstrate that full weld penetration denoting efficient synergetic effect only can be obtained under the appropriate shielding gas parameters. The weld penetration of hybrid welding was determined by the plasma shape varying with the shielding gas parameters, especially the plasma height interacting with incident laser. The full penetrated weld cannot be generated by pure TIG torch method, but can be reached by the hybrid protecting method. The shielding gas parameter range with full penetration weld of the hybrid protecting method combining TIG torch and paraxial nozzle is very narrow, but that of the hybrid protecting method coupling TIG torch and coaxial nozzle is considerably wide.