Combined laser and plasma ARC welding torch and method

A welding torch which combines features of both laser and plasma-arc welding torches. A laser beam (114) is directed by an objective lens (112) so that it is co-linear with the central axis (41) of a plasma-arc torch. The laser beam (114) passes through a planar or conical cathode electrode (116) placed at the bottom orifice of the torch. A coaxial aperture (117) having a diameter less than that of the laser beam is drilled into the cathode (116) to allow the laser beam to pass through the cathode. A constricting nozzle (130) placed under the cathode (116), with the laser beam passing through the axis of the nozzle. As with standard plasma-arc torch, a gas is forced through a chamber having the cathode (116) and nozzle (130) at its bottom end. As the cathode (116) is heated by the laser radiation, the gas is ionized and a plasma-arc is formed. As the laser beam passes through the nozzle (130), it comes to a focus and interacts with the plasma-arc formed between the cathode and a workpiece. The resulting interactions between the plasma-arc and laser beam form a plasma-laser discharge which acts to additionally constrict the laser beam and plasma-arc and increase the energy density of the welding spot formed on the workpiece.