| Electro-spark deposition(ESD)is widely used in surface repair,coating preparation and other fields due to its flexible operation and firm bonding.The understanding of the micro process of deposition restricts the final deposition effect.In order to explore the mass transfer and coating fusion process of electro-spark deposition,the transition process of droplet dropping and droplet contacting,and the process of coating material fusion and solidification process in ESD were simulated and analyzed in this paper,and the simulation results were verified by ESD experiments.This has guiding significance for further revealing the mechanism of ESD and improving the deposition efficiency.(1)Study on the droplet drop process of ESD.Based on the analysis of material melting process in ESD,the geometric model of molten pool was obtained,and the droplet dropping process of ESD was analyzed.Considering the effects of gravity,plasma flow force and surface tension,the droplet dropping transition simulation model was established,and the surface deformation of droplets and the pressure distribution and velocity change in the gap region were analyzed.It is found that the neck velocity is obviously higher than other positions when the droplet falls off,and the highest velocity can reach 4.53 m/s.(2)Study on fusion and solidification process of coating-substrate material.Based on the simulation results of droplet dropping process,the electrode material is regarded as a component of the coating,and the fusion and solidification model of the molten material was established.The simulation of material fusion process was realized in the flow,and the distribution law of different materials in the coating was studied.Through the heat transfer between the molten material and the substrate,the solidification process of coating was simulated,the temperature change in the solidification process was analyzed,and the solidification law of molten materials was studied.The results show that the content of electrode material in the upper layer is higher than that in the bottom.(3)Study on droplet contact transition in ESD.Considering the situation that the electrode material is in direct contact with the molten pool,the droplet contact transition model of ESD was established.The separation of droplets was realized by the flow of materials and the effect of surface tension,and the flow law of materials in the contact process was studied.The flow and solidification process of the separated materials were simulated,the distribution of electrode materials after fusion was analyzed,and the temperature change at different times and the change law of solidification interface were studied.The results show that the material flowing out of the molten pool solidifies first,while the center of the molten pool near the upper surface solidifies finally.(4)Validation test analysis of the simulation model.The single-point experiment of ESD was carried out,the surface morphology of the deposition point was observed,the contours of the deposition area and the simulated coating were compared,and the element distribution on the surface and cross-section of the deposition point was analyzed.It was found that the material distribution in the deposition area was basically consistent with the simulation results.The shape and distribution of the material in the cross-section of the deposition area were observed,and the simulation results were verified laterally.In summary,this paper analyzed the mass transfer process of droplet dropping and droplet contact in ESD by simulation.The fusion and solidification process of coating materials were simulated,and the material distribution in the coating and the solidification law of the molten material were studied.The simulation results are verified by experiments,which contributes to the further study of the deposition process in ESD. |
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