| Sherardizing is a process in which the steel matrix is embedded in the penetrant and then the Fe-Zn alloy layer is obtained by thermal diffusion.The process is mainly used for protection of steel parts.The zinc coating obtained by sherardizing is superior to other zinc coatings in terms of corrosion resistance,and the Fe-Zn alloy coating has a strong binding force with the substrate,so this technology has been widely used.However,the production efficiency and yield of the sherardizing are not high,and most of the quality tests are destructive tests.In addition,the anti-corrosion effect of the zinc coating is limited.For the above problems,the finite element method is used to simulate the distribution of zinc concentration field in the process of sherardizing,and the phase content of the zinc coating is quantitatively analyzed based on the Rietveld method.The two calculation processes are used to guide the production of sherardizing products that meet different phase content.Based on the excellent anti-corrosion effect of manganese in a variety of zinc coatings,Zn-Mn coating is obtained by the pack cementation process and mechanical energy aided diffusing process,and it is expected to improve the anti-corrosion effect of the zinc coating.In this paper,the finite element method is used to simulate the distribution of zinc concentration field in the process of sherardizing.The results show that the simulation results of the finite element method is consistent with the experimental results.This model is more accurate when sherardizing for a short time at low temperature.In addition,the Rietveld method is used to refine the ?,?,? phases contained in the zinc coating,and the refined structural model is used for the quantitative analysis of the phase content of the zinc coating.The error between the quantitative phase analysis results obtained by Rietveld method and the experimental values is less than 8.2%.Compared with other detection methods,this method is relatively simple and highly accurate,which can be used as a non-destructive detection method.The finite element simulation of zinc concentration field and the Rietveld quantitative phase analysis method can guide the production process of sherardizing to some extent.In order to improve the corrosion resistance of the zinc coating,firstly,the Zn-Mn coating obtained by the pack cementation process at 410?,440? and 470? for 3 hours are studied.The results show that the Zn coating obtained at 470? can detect the presence of Mn,while the Zn coating obtained at 410? and 440? does not detect the presence of Mn.When the Zn-Mn coating is prepared by the pack cementation process,the pack powder has been bonded into blocks,which affects the surface quality of the sample.Secondly,the Zn-Mn coating is obtained by means of mechanical energy aided diffusing process.The results show that the Zn-Mn coating with better surface quality can be obtained by means of mechanical energy aided diffusing process,and the adhesion degree of the pack powder is reduced.In the way of mechanical energy aided diffusing,the Zn-Mn coating obtained by one-step temperature increase has many cracks,and the thickness is smaller than the other coating which obtained by the two-step temperature increase.The presence of Mn element in the pack powder can inhibit the rapid growth of the Zn-Mn coating.Through XRD characterization and EDS analysis of the Zn-Mn coating,it is known that the Mn element exists in the ? phase and the ? phase in the form of solid solution.According to the electrochemical test results,the presence of Mn element in the Zn-Mn coating can increase the self-corrosion potential,and reduce the corrosion current density and corrosion rate,that indicating the infiltration of Mn element can better improve the corrosion resistance of the Zn-Mn coating. |
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