| The sherardizing is widely used in the anti-corrosion field of steel products.It is a kind of surface protection method of forming Zn-Fe alloy layer on the steel surface by thermal diffusion.The surface hardness,corrosion resistance,and oxidation resistance of the steel after sherardizing treatment have been greatly improved.However,the production efficiency and yield percentage of sherardizing products are not high,and which restricts the use in extreme environments such as the ocean,it restricts the further development of sherardizing technology.In the face of these problems,ANN-BP model is used to establish the relationship between the parameters of sherardizing process and the thickness of the coating,it can guide the production of products that meet the requirements of different coating thicknesses.Based on the method of multi-component thermochemical treatment,combined with titanium's excellent anti-corrosion performance in the marine environment,the Zn-Ti coating is prepared by the pack cementation process,in order to improve the the marine anti-corrosion resistance of the zinc coating,The thickness of zinc coating is very important to its performance,so it is necessary to put forward a model to predict the thickness of zinc coating with different process parameters.Due to the complexity of the relationship between the thickness of coating and the process parameters of sherardizing,it is often difficult to accurately express it with a functional relation.Based on the three-layer BP neural network of Levenberg Marquardt algorithm,this paper establishes a model of the relationship between the technological parameters of sherardizing and the total thickness of the coating,the thickness of ? phase and ? phase.The results show that the BP neural network model has a good prediction effect on the total thickness of Fe Zn layer,the thickness of ? phase and ? phase,the error of model results is within 4.71%,and the correlation coefficient is 0.99974.It is possible to optimize the process parameters of sherardizing and control the thickness of the infiltration layer through this model,it has important guiding significance for the development of new processes,shortening the research and development cycle and reducing production costs.In order to improve the corrosion resistance of Zn coating,the microstructure and the corrosion resistance of the coating formed at 460?,480? and 500? for 2 hours are studied.The results show that when the Ti content of the permeating agent is higher than 6%,The prepared Zn-Ti coating has a double-layer structure,the outermost layer is Zn-Ti-Fe phase,and the innermost layer is Zn-Fe phase.The Zn-Ti-Fe layer is formed by replacing Zn in the Zn-Fe layer with Ti,and the Fe in the Zn-Fe layer diffuses into the Zn-Ti-Fe layer in a large amount.The higher the holding temperature or the more Ti content,the thickness of the prepared Zn-Ti coating is thinner.The surface of the Zn-Ti coating is relatively loose and porous,these holes are formed by the evaporation of Zn above the melting point.And with the increase of Ti content,the porous structure becomes more and more.It was found through electrochemical tests that the corrosion current density of the substrate,the Zn infiltration layer,and the Zn-Ti infiltration layer are decreased in sequence.This show that both Zn and Zn Ti coating can significantly improve the corrosion resistance of iron-based materials,and the corrosion resistance of Zn Ti coating is better than that of Zn coating... |
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