Product Code: PIC2008_206

Numerical and Experimental Investigation of Thermal Stresses and Distortions in the Induction Assisted Laser Cladding
Authors:
Dietrich Lepski, Fraunhofer Institute for Material and Beam Technology Iws; Dresden Germany
Frank Brückner, Fraunhofer IWS Dresden; Dresden Germany
Eckhard Beyer, Fraunhofer Institute for Material and Beam Technology Iws & Lot/Iof Dresden University of Technology; Dresden Germany
Presented at PICALO 2008

In the laser cladding process the powdery coating material is resorbed by the laser induced melt pool and strongly joint to the subjacent substrate. The very high gradients of the laser induced temperature field as well as density changes due to phase transformations in the substrate may result in high thermal stresses, which can cause cracking and delamination especially in the case of very hard coating materials. These stresses can be reduced by an improved process management including the integration of electro-magnetic heat sources for pre- and post-weld heating, which are able to decrease temperature gradients and cooling rates and even to suppress the undesired formation of martensite. Depending on the type of application the stress states of single beads, of surface coatings on bars and plates as well as of volume built-ups were simulated by finite element calculations, which enable an improved understanding of the process phenomena and of the stress reduction to be achieved by integrated inductors. These calculations have been validated by accompanying experiments, which especially deal with cracking, workpiece distortion, and metallurgical changes. The processing of the inductive pre- and post-weld heating was optimized with respect to the required input of heat into the workpiece.