Product Code: ICAL06_1005

Improving Laser Cladding Process Conditions by Inducing Skin Effect through High Frequency Magnetic Field
Authors:
Jean Pierre Bergmann, TU Ilmenau; Ilmenau Germany
Johannes Wilden, TU Ilmenau; Ilmenau Germany
Markus Dolles, TU Ilmenau; Ilmenau Germany
Presented at ICALEO 2006

Laser beam cladding represents a technology, which allows high quality coating technique 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 ensuring 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. 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 in order to improve process properties. 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. Lorentz forces can be induced when a magnetic field is set and contemporarily a current flows through the processed area. First investigations with a permanent magnet are already published and show the success of the strategy, even if the effect are restricted due to the fact, that a part of the current flows in the cold material. The set of high frequency magnetic fields allows inducing a current flow on the surface due to the skin effect. The current interacts with the magnetic field and generates magnetic forces in the surface layer of the melt pool. These additional forces make it possible to adapt the coating geometry to the requirements of the application. The paper will deal with the experimental set up as well as with the optimization of form and geometry of the inductor. Further more the physical background of the technique, the influence of different process conditions will be discussed and confirmed through experimental investigation.