Powder Flow Field and Light-powder Coupling Mechanism of Inclined Plane Laser Cladding

At present, the research on the numerical simulation of powder flow is mainly based on the working ranges of nozzles and flat substrates, which greatly limits the application of laser cladding in repairing inclined substrates. Meanwhile, the existing research on the powder flow field of laser cladding is based on the single factor way. The response surface methodology (RSM) was used to design the simulation scheme and process the data in the work. The mathematical model between the input and output parameters was fitted to explore the effects of powder feeding voltages, gas flow rate and inclination angles of substrates on the powder particle velocity, powder concentration, and powder spot diameter on inclined substrates. The convergence of powders was studied by numerical simulation and experiments to explore the coupling of optical powders and the effects of their balance relationships on coating morphologies. Ni35A powders (with an average particle size of 1 × 10–4 m) were used for simulation and experiments, and 45# steel (40 × 20 × 10 mm) was used as the base material in experiments. Powder beam conically converged and then conically diverged from the nozzle outlet in the simulation of the powder flow field. The convergence positions were consistent with actual powder flow fields captured by high-speed cameras, which verified the reliability of the model. Meanwhile, the simulation of the powder flow field was carried out according to the simulation scheme, and the powder-particle velocity increased with the increasing gas flow rate. Maximum powder concentration on inclined substrates decreased with the increasing gas flow rate, but increased with the increasing powder feeding voltage. The powder spot diameter on inclined substrates increased with the increasing inclination angles of substrates and gas flow rate. The simulation results were verified experimentally. When other process parameters were constant, the greater the powder concentration on the substrate was, the greater the cladding area was. When the powder feeding voltage increased from 10 to 26 V, the area of the cladding layer increased accordingly. When the gas flow rate decreased from 30 to 6 NL/min, the area of the cladding layer increased accordingly. When inclined substrate angle θ increased from 0° to 40°, the area of the cladding layer decreased accordingly. The law obtained from the simulation was consistent with that of the experiment. Therefore, the model had important guiding significance for selecting process parameters in the actual cladding process. The model had high prediction accuracy for maximum powder concentration and powder spot diameter on inclined substrates. The optimization objectives included the maximum powder concentration and the minimum powder spot diameter on inclined substrates. The errors between the simulated and predicted values of maximum powder concentration on 0°, 10°, 20°, and 30° inclined substrates were 4.34%, 3.61%, 5.82%, and 13.15%, respectively and those of powder spot diameters on the inclined substrates were 2.95%, 3.22%, 3.57%, and 4.10%, respectively. Optical powder coupling showed that when laser power was constant, the metal powders and laser energy densities were balanced with a high utilization rate of powders and a circular coating morphology. The powder utilization rate was low, and the coating morphology was oval for fewer metal powders. The laser energy density was not enough to melt too many metal powders, and coatings could not be combined with substrates and were easy to fall off. The results provide important guidance for selecting parameters in applying laser cladding to inclined part repairing. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.