Plasma welding with a superimposed coaxial fiber laser beam

A new laser-assisted plasma arc welding process with a coaxial arrangement of arc and plasma was developed. A low-power fiber laser beam (lYb = 1.07 mm) with maximum power of 300 W is guided through a hollow cathode. This combined process is of special interest regarding the costs and power input. Experiments show higher arc stability and welding efficiency due to the additional laser power. Of special interest for the investigations were the reasons for the synergic effects. Therefore, the experimental setup was enhanced by a laser displacement inside the hollow plasma cathode. The laser spot can lead or trail the arc, but the laser beam remains virtually coaxial to the arc. The different spot positions influence laser absorption on the surface and the creation of the weld seam. In order to maximize the effect of different temperature distributions due to the laser, stainless steel AISI 304 (X5CrNi18-10) was used as base material. Different plasma nozzle diameters were investigated on their influence on arc stabilization and melting efficiency by additional laser radiation. Hypothesis of the work presented is that higher arc stability and weld efficiency is caused by effects at the work piece and not in the arc column.