Monte Carlo simulation of plasma spray coating microstructure

Based on the analysis of the electronic scanning microstructure of plasma sprayed coatings, a set of basic rules for layer formation, interaction and pore formation are formulated, and a numerical model for plasma sprayed coating formation is established by Monte Carlo method to predict the microstructure and microstructure of the coating. Its porosity and surface roughness characteristics, and discuss the influence of powder particle size and speed, spray gun moving speed and spraying distance. The simulation results show that the pore distribution in the coating microstructure predicted by the model is uneven, which is consistent with the experimental results; the porosity and roughness of the coating decrease with the increase of droplet impact speed and diameter, but when When the impact speed exceeds 160 m/s, the effects of both are reduced; changing the scanning speed of the spray gun during the spraying process, the porosity and roughness of the coating do not change significantly; the increase of the spraying distance will make the porosity of the coating And the roughness is reduced.

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Plasma spraying technology is widely used in various industrial fields due to its advantages of wide range of sprayable materials, high spraying efficiency, and good coating quality. The performance of plasma spray coating directly determines its final use conditions, and porosity and roughness are one of the most important factors affecting the quality of the coating. Therefore, it is important to study the influence of process parameters on the porosity and roughness of the coating. significance. The porosity and roughness of the coating are related to many process parameters of the spraying process, such as the powder particle size, the scanning speed of the spray gun, and the distance between the spray gun and the substrate. The traditional method is to obtain empirical data through repeated trials to select process parameters, which is time-consuming and costly.

With the development of computer technology, many researchers in recent years have begun to use numerical simulation methods for research and have made substantial progress. Cirolini et al. established a set of rules for coating growth and pore formation to simulate the microstructure and porosity of thermal barrier coatings. Chen et al. considered the spraying angle not 90°, and predicted the effect of spraying angle on the porosity of the coating. influences. The pores inside the actual coating often form a network structure, and it is difficult to fully present the internal structure information of the coating in a two-dimensional cross-section. Ghafouri-Azar et al. extended the model to a three-dimensional situation and assumed that the pores were formed only by Due to the warpage of the laminate, Xue et al. believed that the warpage of the laminate was only applicable to metal laminates, and then extended the model of Ghafouri-Azar et al. to the application range of ceramic coatings. Bobzin et al. used the coupling of CFD and FEM models to predict the coating deposition process, and got rid of too many assumptions about coating accumulation and pore formation. However, due to the limitation of computer computing power, their model can only predict coatings in the micrometer range. This paper uses the Monte Carlo method to establish a random model to predict the microstructure, porosity and roughness of plasma sprayed coatings, and study the influence of process parameters on the porosity and surface roughness of the coating.

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In the plasma spraying process, the metal or non-metal powder material is fed into the high temperature and high speed plasma jet under the action of the powder carrier gas, is heated, accelerated, and hits the substrate at a very high speed to spread and solidify to form a layer Then the plies are stacked to form a coating. According to the formation process of spray coating, the establishment of the model is summarized in the following three processes: ①Powder parameter model———The heating and acceleration process of powder particles; ②Layer formation model——— Spreading and solidification process of layers; ③Layer stacking model———Layer stacking and coating forming process.

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Under proper process parameters, most powder particles can be heated to a molten state by the jet before reaching the substrate. Therefore, this article assumes that the molten droplet is in a completely melted state before hitting the substrate, and the substrate is preheated to above the critical temperature. After the droplet hits the substrate, it does not splash, and finally spreads and solidifies into a disc-shaped layer, as shown in. It is a scanning electron microscope (SEM) image of a typical molten droplet hitting the substrate and spreading to form a disc-like morphology.

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Based on the analysis of the coating formation mechanism, this paper uses the Monte Carlo method to establish a plasma sprayed YSZ coating formation process model, predict the microstructure of the coating and its porosity and roughness, and study the droplet diameter, velocity, The effect of spray gun scanning speed and spraying distance on the porosity and roughness of the coating. The results show that the microstructure predicted by the model is consistent with the experimental results; the porosity and roughness of the coating decrease with the increase of the droplet impact velocity, but this effect weakens when the impact velocity exceeds 160 m/s The increase of the spraying distance reduces the porosity and roughness of the coating; the scanning speed of the spray gun during the spraying process has no obvious regularity in the influence of the porosity and roughness of the coating.

Founded in 2015,Zunhua Baorui Titanium Equipment Co.,Ltd. is a manufacturer specializing in pvd vacuum ion coating equipment. The company’s products mainly include large plate coating machine, large tube collating machine, tool coating machine and LOW-E glass production line. Mr.Wang baijiang ,general manager of the company ,has been engaged in vacuum coating industry for more than 30 years. He continuously improve production technology, improve product performance and devote himself to provide customers with better product experience and higher production efficiency.