【作者】 辛铁柱；

【导师】 赵万生；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2006， 博士

【摘要】 微弧氧化技术又称为微等离子体氧化技术或阳极火花沉积技术,这是一种在阀金属及其合金表面通过微等离子体放电,进行复杂的电化学、等离子化学和热化学过程,原位生长氧化物陶瓷膜的新技术。利用此项技术形成的表面膜层与基体的结合力强、硬度高、耐磨性、耐蚀性、抗热震性高,膜层电绝缘性好、击穿电压高。不仅如此,该技术采用能量密度极高的微等离子弧加热的先进加热方法,基体组织结构不受影响,且工艺不复杂,不造成环境污染,是一项很有前途的材料表面处理新技术,正成为国际材料表面工程技术领域的研究热点。俄罗斯、美国、英国及日本等国对这项新技术的研究十分重视。铝合金表面的微弧氧化是一个十分复杂的过程,包含初期氧化膜的电化学形成,以及后续的陶瓷膜击穿,其中包含热化学、电化学以及光、电、热等物理作用,并且这一过程受基体本身的材质、电源参数以及电解液的参数影响,很难在线监测,这就为理论研究带来困难。因此,到目前为止,仍没有一种理论模型能圆满地解释各种实验现象,对其机理研究仍需进一步的探索和完善。本文通过对铝合金表面微弧氧化陶瓷膜的生成机理、工艺规律、工艺试验及生成陶瓷膜特性的系统研究,以求进一步掌握和了解铝合金表面微弧氧化加工新技术,为推进该技术的产业化和深层次的研究打下良好的基础。微弧氧化过程的机理是这一技术的理论基础,本文首先对铝合金表面微弧氧化生成陶瓷膜的机理进行了深入研究,提出了微弧氧化过程的机理模型。认为由于在微弧放电通道内气体压力较高,在此压力范围内电子不可能被电场充分加速,其能量经碰撞被高密度的气体分子有效地吸收而变成热能,使体系达到热平衡,此时电子的温度Te和气体的温度Tg相同,即Te=Tg。微弧氧化过程中产生的等离子体主要为氧的等离子体,孔底的氧气泡首先被击穿,产生氧的等离子体,这一过程产生的自由电子和焦耳热,又引发孔底氧化膜的雪崩击穿,氧化膜的击穿可以认为发生在阻挡层有瑕疵的弱斑上,这个弱斑是阳极氧化时氧化膜产生晶格缺陷的地方。整个放电通道的等离子体在电场的作用下发生正离子的迁移,在阴极处(溶液与陶瓷膜的界面)留下正的空间电荷,这些空间电荷增大了阴极的电子场发射,以此来保证电流的连续性并且使雪崩可能发展到足以引起持续的击穿。氧等离子体中存在着激发态的氧分子和氧原子,这些都是活性物质,在微弧氧化过程中起着重要的作用。用高速快门的照相机(快门速度为1s/1000)拍下了阳极表面的放电点状况。可以看出,工件表面同时放电的通道数量很多。更多还原

【Abstract】 Micro-arc oxidation (MAO) also prefered to as micro plasma oxidation or anode spark deposition, is a new complex plasma-discharge process, involving electrochemical, plasma chemical, and thermochemical processes, which is used to produce ceramic film in situs on the surface of valve metal or their alloy’s. The coatings prepared by this process have excellent performances in terms of adhesion, hardness, friction, corrosion-resistance and dielectric properties. This technique adopts an advanced heating up method employing micro-plasma with ultra high energy density, and does not affect the structure of substrate; it is not a difficult process and does not induce environmental pollution as well. At present, Russia takes the lead not only in academic research but also in application. This technology also draws close attention of western countries. China has developed this technique in recent years.Micro-arc oxidation is a compelx process, which involves electrochemical chemical, optical, electrical and thermal processes. It is combined with the formation of oxide film formed by electro-chemistry and the following breakdown of ceramic coating, and influenced by parameters of substrates, power supply and electrolyte. It is too complex to inspect online, so there is no academic model that can explain various experiment phenomena. Research on mechanism should be conducted further and perfectly.In this dissertation, the mechanism of MAO, technical regularity, technical experiments and the characteristics of MAO coating were studied systemically for the purpose of the grasp, further research and industrialization of this technology.Formation mechanism is a theoretical foundation of MAO process. So at first the mechanism of MAO was analyzed, and the mechanism and academic model of MAO was also studied. The result shows that in discharge channel the temperature of electron (Te) is equal to that of gas (Tg), because electron can’t be accelerated enough under the high pressure in the channel, and the energy was absorbed as heat efficiently through collision.The plasma produced in MAO process is mainly consisted of oxygen. The oxygen bubble in the hole was firstly broke down, and the oxygen plasma is produced. The ceramic coating was broke down by the joule heat and free electron更多还原