Laser beam cladding represents a technology, which allows high quality coating properties towards other thermal coating processes as for example a good metallic bonding between coating and base material, a fine microstructure and good mechanical properties due to the rapid cooling are reached. Moreover the very small dilution allows to ensure the desired metallurgic properties in for example a one layer cladding. Nevertheless the spreading of laser cladding in industrial production is very limited, as on the one side the process efficiency is very low and on the other hand the investment costs are very high compared to the actual benefits.
During cladding a coating material, which can be feed in form of powder or filler metal, is molten together with a restricted part of base material and the melt bath spreads on the surface of the component. If its possible during the short interval before solidification to actively form the melt bath, for example widening, flexibility as well as acceptance of laser cladding can be improved.
The application of additional forces, which are generated during process and actively influence processing conditions enhance the efficiency of industrial processes. Magnetic forces represent one example. Damping of the melt movement in steel casting or the stirring of electric conductive fluids through rotating magnetic fields are some applications, in which the potential of additional electromagnetic is set in industry.
The flexibility and the effectiveness of laser cladding can be widely increased through free forming (shaping) of the coating. The geometric shape of the coating seam is mainly defined by gravity and surface tension of the melt. An additional force, as for example Lorentz force, can optimize the geometry. Wide coatings allow for example a low number of overlapping layers when coating large areas. Slim coatings on the contrary are advantageous when generating 3-dimensional structures. The resulting claddings show due to the orientation of the induced forces a different cross section. Accordingly a flat geometry is useful to apply large coatings and a small and high geometry increases the efficiency for the generation of filigree structures.
Lorentz forces can be induced when a magnetic field is set and contemporarly a current flows through the processed area. The presented investigation clarifies physical background and suitability when processing technical coatings. Furthermore the paper reports about the different influences towards the process, for example cladding parameters, material properties and strength of the magnetic field.
Due to the easy variation of the magnetic field and the electric current it is possible to vary the geometry during the running process and to adjust the cladding towards the local requirements.