Finite element analysis of effects of dynamic preheating on thermal behavior of multi-track and multi-layer laser cladding

Abstract

Laser cladding technologies has received wide attention since its low dilution and high deposition efficiency. However, the high cooling rate and the temperature gradient due to the rapid heating and cooling characteristic could cause excessive thermal stress and even crack in the coating. In this paper, a dynamic preheating method, in which an additional heat source is applied to heat the localized region ahead of the moving molten pool, was proposed with the intent of solving these problems. A three-dimensional finite element model was established to explore the effect of the dynamic preheating on the thermal behavior of the multi-track and multi-layer laser cladding. The laser cladding experiment was performed to verify the accuracy of the heat transfer model. The simulated thermal cycle curves are in agreement with the experimental thermal history. The calculated results show that the temperature gradient in the depth direction and the cooling rate decrease with the increasing layers. The appropriate process parameter, such as thermal flux density, interaction time, and preheating distance leads to the decrease of the cooling rate and the maximum temperature gradient. Thus it is illustrated that dynamic preheating is contributed to the reduction of the thermal stress and the cracking probability.