Consider the multi-field coupling influence mechanism of different spot sizes in the laser cladding process of Fe31 under the effect of light powder

Abstract To address the unclear mechanisms regarding how different spatial energy distributions of laser spots affect powder-laser interaction and multi-physical field responses in the melt pool during off-axis powder feeding laser cladding on curved substrates, this study conducted a comparative investigation on powder transport and cladding processes under rectangular and circular laser spot conditions. Continuous-discrete phase and thermo-fluid-stress multi-field coupled numerical model was established for laser cladding of Fe31 powder with off-axis powder feeding on a Q235 curved substrate. The model employs a 1200 W laser power, a scanning speed of 6 mm/s, and a powder feed rate of 10 g/min. Considering the particle size distribution and the temperature-dependent thermal properties of the material, it conducts a comparative analysis of the transient evolution of powder temperature, concentration, flow velocity, as well as the temperature field, flow field, and stress field in the melt pool under both rectangular and circular beam spot conditions. The results show that, under the same total laser power, the rectangular light spot has a wider and more uniform energy distribution area, reducing the concentration of local heat input. When the laser irradiation lasts for 2 seconds, the maximum flow velocity of the rectangular light spot increases by approximately 21.1%; the maximum transient thermal stress decreases by approximately 7.9%. The rectangular light spot model was subjected to 12 repeated measurements using infrared thermal imaging experiments, and the relative error between the simulated temperature and the experimental measurement results was 1.47%. The calculations show that, rectangular light spots have a more uniform distribution of heat input, which can reduce local peak temperatures and alter the flow and stress distribution characteristics of the molten pool. This study provides a theoretical reference for the selection of different light spot shapes and the optimization of process parameters in oblique-axis powder-fed laser cladding.