FEM calculations of thermally induced stresses in laser cladded coatings

Laser cladding is a modern technology for the precise generation of coatings, for the repair and maintenance of tools, and for rapid prototyping. Thereby the molten coating material is welded on the substrate without large dilution of the coating with substrate material. Thermal contraction during cooling leads to tensile stresses in the coating which may cause cracks and delamination, in particular in the case of very hard coating materials and at high feed rates as required for the efficient generation of wear and corrosion resistant coatings. Aim of this work is a better understanding of the influence of various parameters such as temperature-time cycles, phase tansformations, and the geometrical conditions on the stress and strain evolution. This opens possibilities to minimize the danger of cracking by an appropriate process management. First stress and strain fields at a single weld bead were calculated numerically for various process parameter sets. Thereafter stress states have been calculated for overlaying weld beads since the coating stresses depend strongly on the mutual interaction of these beads and on the track pattern chosen. Tensile stresses can be reduced by using additional inductive heat sources for pre- and post-weld heating, which decrease the high laser-typical temperature gradients. Entnommen aus <a_href="http://www.fiz-technik.de/db/b_tema.htm" target="_blank">TEMA</a>