Plasma characteristics of a novel coaxial laser-plasma hybrid welding of Ti alloy.

• A novel laser-plasma arc hybrid welding system is developed, which solves the dilemma that coaxial recombination is challenging to achieve before. • The composite plasma in coaxial laser-plasma hybrid welding can make the heat redistribution. • The plasma morphology of hybrid welding turns to be drum-shaped from bell shape, indicating heat redistribution between heat sources. • The electron temperature Te and ion density Ni of the plasma arc is calculated and analyzed by Langmuir double probe. A novel coaxial laser-plasma hybrid welding method defined as "laser-soft plasma coaxial hybrid welding" was developed and studied. The plasma characteristics evolution, including plasma morphology, static electrical characteristic, and physical information of this welding method, was studied with the based material of TC4 alloy. Laser welding and plasma welding were carried out and used as comparative experiments. The plasma morphology of hybrid welding combines the characteristics of laser-induced plasma and arc plasma. The static electrical characteristic indicates that laser and plasma interact and influence each other but with different mechanisms under different current conditions. Physical information such as plasma electron temperature and ion density show that composite plasma can rapidly increase the heat source energy and ionization rate. To sum up, the coaxial plasma arc can increase the laser effect and redistribute the heat of the compound heat source, leading to a widened bead weld and better welding gap adaptability. This work provides an effective method and reference for hybrid welding process design and control in the practical industry. [Display omitted] [ABSTRACT FROM AUTHOR]