Characterization of low-power pulsed laser-induced single/double arc hybrid heat source bottoming welding of medium-thick plate titanium alloy

In order to study the heat source characteristics and discharge mechanism of low power pulse laser induced arc/ double arc hybrid welding technology in the narrow gap backing welding process of titanium alloy medium-thick plate, laser-TIG (L-TIG) hybrid welding and laser-double TIG (L-DTIG) hybrid welding technology were used in this paper. Welding experiments were carried out under different blunt edge thicknesses. Two kinds of welding methods were used to compare the influence of the temperature field of the weld, the morphology of the coupled plasma and the energy distribution of the plasma, the coupling driving force and the force state of the plasma, and the influence of the microstructure and properties of the weld. The results show that the welding heat input of L-DTIG is significantly lower than that of L-TIG hybrid heat source, and there is a larger process interval in the backing welding of different blunt edge thicknesses. Under the action of pulsed laser, the L-DTIG hybrid heat source plasma has a larger central conductive area and electron density, which are 1.68 times and 1.42 times of the L-TIG hybrid heat source, respectively. Due to the small heat input of L-DTIG hybrid welding, the grain size is significantly reduced, so that the hardness of the weld zone and the heat affected zone is slightly higher than that of the L-TIG hybrid heat source, and the hardness distribution from the weld center to the base metal shows a downward trend. Due to the stronger induction and compression ability of the pulsed laser to the double TIG arc, the energy density of the L-DTIG hybrid heat source is more concentrated, which is beneficial to reduce the welding heat input and improve the welding efficiency and the overall performance of the welded joint.