Product Code: ICAL07_1301

Simulation of Thermal Stress in Induction-assisted Laser Cladding
Authors:
Dietrich Lepski, Fraunhofer IWS Dresden; Dresden Germany
Frank Brückner, Fraunhofer IWS Dresden; Dresden Germany
Eckhard Beyer, Fraunhofer IWS Dresden; TU Dresden LOT / IOF; Dresden Germany
Presented at ICALEO 2007

In laser cladding powder particles of wear and corrosion resistant materials are deposited on the workpiece and melted by the laser beam to get a strong weld joint. High temperature gradients and density changes due to phase transformations arising during cooling are responsible for the evolution of thermal stresses, which even may cause cracks and delamination. This effect becomes more pronounced at higher feed rates and restricts the efficiency of the cladding process and the use of hard coating materials. Tailored temperature fields consisting of a flat base and a steep peak lead to strongly reduced stresses without affecting the high precision of the laser process. To this end the laser cladding is accompanied by pre- or post-weld heating using electromagnetic heat sources. The influence of process parameters and material properties on the residual stresses can be better understood by simulating the stress evolution. Therefore, transient finite element stress calculations were performed for single weld beads as well as for coating layers and volumes built up of a large number of overlapping weld beads. From the results sets of process parameters were derived for the induction-assisted laser cladding which significantly reduce the stress levels and thus the danger of cracking.