微弧氧化技术实验设备的研制及其反应机理研究

发布时间：2018-06-13 13:52

本文选题：微弧氧化 + 电参数　；参考：《清华大学》2015年硕士论文

【摘要】：地球上可开发的矿产资源日益短缺,提高材料利用率及使用寿命成为材料研究领域的重要课题。微弧氧化技术处理材料的对象主要有铝、镁、锆、钛及其合金,将这些金属作为阳极置于强电场的电解液中,其表面与溶液准阴极在强电压作用下发生弧光放电,局部产生高温高压,使金属原子与溶液中的氧结合,最终在金属表面形成一层坚固的陶瓷氧化膜,该膜层可以极大地改善金属材料本身的耐磨、耐热、耐腐蚀性能。微弧氧化技术工艺简单,不引入毒害物质,对加工零件形状没有特殊要求,所制备的陶瓷氧化膜兼具阳极氧化膜和陶瓷喷涂层的优点,作为防腐蚀膜层可应用在航空航天,造船、化学设备、建筑、泵体等关键部位;作为耐磨膜层可应用在机械轴承,汽车发动机,纺织机械,管道等;作为热防护层可应用在电器电子,化工,能源工业设备等;作为功能性膜层,可应用于生物催化,医疗设备,医用材料等,微弧氧化技术在各工业领域有着良好的应用前景。本文总结了微弧氧化技术机理,将微弧氧化过程分为阳极氧化、电击穿起弧、膜层增厚、断电冷却四个阶段。分析了溶液中各溶质成分对微弧氧化过程的影响,确定了选取适当的主盐,pH调节剂,络合增厚剂,成膜促进剂为添加剂的微弧氧化溶液体系。本文设计了一套微弧氧化设备,针对LY12铝合金,采用正负脉冲电源,通过一系列微弧氧化实验,首先确定了铝合金与溶液形成阳极氧化膜的击穿电压,然后研究了各电参数如电压幅值,实验时间,电源频率,占空比以及反向脉冲对微弧氧化成膜结果的影响。针对不同功能要求的膜层,提出了定性的电参数设置方案,并在此基础上分析了各电参数对微弧氧化过程的作用机理。本文研究结果表明:1.LY12铝合金在硅酸钠溶液体系中的击穿电压为300V,在较低电压下虽能形成氧化膜层,但是膜层厚度不连续,在金属表面附着不均匀。在300V及以上电压中,均能得到连续均匀的膜层。2.微弧氧化膜层性能取决于每次脉冲提供的能量大小、频率以及持续时间,能量越大,膜层生长越快越厚,但膜层多孔疏松;频率越高,膜层生长速率有所下滑,但膜层内部结构更加致密;持续时间越长,膜层生长快,但膜层致密性不好。3.根据微弧氧化过程的四个阶段,提出了变电参数的加工模式。前期电击穿起弧阶段采用低频率,低电压,适中的占空比的加载模式,后期膜层生长阶段采用高频率,高电压,低占空比的加载模式,膜层性能比单一电参数得到了极大改善。
[Abstract]:There is a growing shortage of mineral resources on the earth. Improving the utilization ratio and service life of materials has become an important subject in the field of materials research. The main objects of micro-arc oxidation technology are aluminum, magnesium, zirconium, titanium and their alloys. When these metals are used as anode in the electrolyte with strong electric field, arc discharge occurs between the surface and the quasi-cathode of the solution under the action of strong voltage. A strong ceramic oxide film is formed on the metal surface which can greatly improve the wear resistance heat resistance and corrosion resistance of the metal material. The micro-arc oxidation technology is simple, does not introduce toxic substances, and has no special requirements for the shape of machining parts. The prepared ceramic oxide film has the advantages of both anodic oxide film and ceramic spray coating, so it can be used in aerospace as an anticorrosive film. Shipbuilding, chemical equipment, building, pump body and other key parts; as wear-resistant film layer can be used in mechanical bearings, automobile engines, textile machinery, pipes, etc.; as thermal protection layer can be used in electrical, electronic, chemical, energy industry equipment, etc. As a functional film, it can be used in biocatalysis, medical equipment, medical materials and so on. The technology of micro-arc oxidation has a good application prospect in various industrial fields. In this paper, the mechanism of micro-arc oxidation is summarized. The process of micro-arc oxidation is divided into four stages: anodic oxidation, electric breakdown of arc, thickening of film, and cooling of power off. The effect of solute composition on the process of micro-arc oxidation was analyzed. The solution system of micro-arc oxidation was determined by selecting appropriate pH regulator of main salt, complexing thickening agent and film forming accelerator as additives. In this paper, a set of micro-arc oxidation equipment is designed. For LY12 aluminum alloy, the breakdown voltage of anodic oxide film formed by aluminum alloy and solution is determined by a series of micro-arc oxidation experiments using positive and negative pulse power supply. Then the effects of various electrical parameters such as voltage amplitude, experimental time, power frequency, duty cycle and reverse pulse on the results of micro-arc oxidation film formation are studied. According to the different functional requirements of the film, a qualitative electric parameter setting scheme is proposed, and on this basis, the action mechanism of each electric parameter on the micro-arc oxidation process is analyzed. The results show that the breakdown voltage of 1% LY12 aluminum alloy in sodium silicate solution system is 300V. Although the oxide film can be formed at a lower voltage, the thickness of the film is not continuous and the coating is not uniform on the surface of metal. At the voltage of 300V and above, a continuous and uniform film layer of. 2 can be obtained. The performance of the micro-arc oxide film depends on the energy supply, frequency and duration of each pulse. The larger the energy, the faster and thicker the film is, but the more porous the film is, the lower the growth rate of the film is. However, the inner structure of the film is denser, and the longer the duration is, the faster the film grows, but the denser the film is, the smaller the density of the film is. According to the four stages of the micro-arc oxidation process, the processing mode of the transformer parameters is put forward. The loading mode of low frequency, low voltage and moderate duty cycle is used in the early stage of electric breakdown and starting arc, and the loading mode of high frequency, high voltage and low duty cycle is adopted in the later growth stage of the film. The performance of the film is greatly improved compared with a single electric parameter.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ153

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