提高TC4合金微弧氧化膜层显微硬度的研究

发布时间：2018-05-28 07:25

本文选题：TC4合金 + 微弧氧化　；参考：《长安大学》2017年硕士论文

【摘要】：微弧氧化技术可以在钛合金表面生长一层陶瓷膜层,且不会改变合金内部结构与力学性能。但是,目前所研究的膜层硬度偏低,而在剧烈摩擦环境下对膜层的硬度有较高的要求,因此需研究能够提高膜层显微硬度的微弧氧化处理工艺。本文通过在不同主盐溶液、不同电参数和不同有机添加剂的条件下,系统的研究了膜层显微硬度随参数的变化规律,并通过SEM、EDS、XRD等测试手段对膜层的微观形貌、元素分布和相组成进行分析。研究发现,膜层相组成是影响膜层显微硬度的主要因素之一。铝酸盐溶液中膜层的显微硬度最高,但膜基结合最差,锆盐溶液膜层显微硬度次之,磷酸盐和硅酸盐溶液中所得膜层硬度无明显区别。在硅酸盐、磷酸盐、铝酸盐和锆盐溶液中对TC4合金微弧氧化处理,锆盐溶液下的起弧电压相对最低,膜层表面粗糙度最小。起弧电压随主盐浓度的增大均逐渐减小。在锆盐溶液中,随时间的增长,微弧氧化膜层厚度逐渐增大,表面孔隙率和粗糙度也逐渐变大,膜层中ZrO2的含量逐渐减小,膜层表面显微硬度先增加后减小。随电压的增大,膜层表面微孔数量减小,孔径逐渐变大,表面致密性下降,显微硬度随电压升高呈先增后减趋势。锆盐溶液中制备高硬度微弧氧化膜层的最佳工艺参数为:氧化时间15 min,电压420 V,占空比15%,脉冲频率500 Hz。醇类添加剂和胺类添加剂均可使膜层表面结构致密,微孔分布均匀。在添加丙三醇、N,N-二甲基甲酰胺、脲的溶液中制备的微弧氧化膜层中生成新相TiC提高膜层显微硬度。醇类添加剂中丙三醇的加入对膜层硬度的提高有促进作用,胺类添加剂中N,N-二甲基甲酰胺、三乙醇胺、脲均可提高膜层显微硬度,其中脲的加入对膜层显微硬度的提高最显著。整体上,胺类添加剂比醇类添加剂更能有效提高膜层显微硬度。
[Abstract]:A ceramic film can be grown on the surface of titanium alloy by micro-arc oxidation without changing the internal structure and mechanical properties of the alloy. However, the hardness of the film studied at present is on the low side, and the hardness of the film is very high under the severe friction environment. Therefore, it is necessary to study the micro-arc oxidation process which can improve the microhardness of the film. In this paper, the variation of microhardness with different parameters was studied systematically under the conditions of different main salt solution, different electric parameters and different organic additives, and the microstructure of the film was measured by means of SEM EDS XRD and so on. Element distribution and phase composition were analyzed. It is found that the phase composition of the film is one of the main factors affecting the microhardness of the film. The microhardness of the film was the highest in the aluminate solution, but the lowest in the film base, followed by the microhardness in the zirconium salt solution, but there was no obvious difference between the hardness of the film in phosphate solution and that in the silicate solution. In silicate, phosphate, aluminate and zirconium salt solutions, the arc starting voltage and the surface roughness of TC4 alloy are the lowest and the lowest respectively. The arcing voltage decreases with the increase of the concentration of the main salt. In zirconium salt solution, with the increase of time, the thickness of micro-arc oxide film increases gradually, the surface porosity and roughness increase gradually, the content of ZrO2 in the film decreases gradually, and the surface microhardness of the film increases first and then decreases. With the increase of voltage, the number of micropores on the surface of the film decreases, the pore size becomes larger and the surface compactness decreases. The microhardness increases first and then decreases with the increase of voltage. The optimum process parameters for preparing high hardness microarc oxide film in zirconium salt solution are as follows: oxidation time 15 min, voltage 420 V, duty cycle 15, pulse frequency 500 Hz. Alcohol additives and amine additives can make the surface structure of the film compact, and the distribution of micropores is uniform. A new phase TiC was formed in the micro-arc oxide film prepared by adding N-dimethylformamide and urea in the solution of triglyceride to improve the microhardness of the film. The addition of glycerol in alcohol additives can promote the increase of film hardness. N- N- dimethylformamide, triethanolamine and urea can increase the microhardness of the film, and the addition of urea can increase the microhardness of the film. As a whole, amine additives are more effective than alcohol additives in improving the microhardness of the film.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.45

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