电弧喷涂固液复合工艺研究

发布时间：2018-03-20 06:47

本文选题：电弧喷涂　切入点：复合铸造　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：热喷涂作为表面工程领域里应用最多的技术之一,具有施工灵活,实用性强,应用面广,生产效率高等特点,在防腐、耐磨等领域得到广泛运用。但热喷涂涂层与基体结合方式一般是机械结合,很容易发生涂层剥落,限制了热喷涂技术的应用。为了提高涂层和基体的结合强度,本文采用复合铸造的技术来实现基体和涂层之间的冶金结合。首先通过热喷涂技术在型芯表面喷涂一层涂层,将熔融的金属液浇注到模具中实现涂层和基体的结合,该方法改变了传统热喷涂工艺先有产品本体后有喷涂层的观念束缚,为涂层和基体的连接提供了一种全新的思路。本文通过控制基体材料、预处理、铸造过程和后处理工艺,研究界面的结合情况,得到如下结果和结论:①通过固液复合铸造的方法,成功制备出了具有冶金结合界面的Al/Al、Al/A356和Al/AZ91复合铸件,说明该方法具有可行性并可应用于多种材料。②铝涂层表面氧化膜对界面的结合有重要的影响。在铝基体和铝涂层液固复合的过程中,该氧化膜将阻碍界面间的润湿,对涂层进行表面处理破碎这层氧化膜将促进界面生成冶金结合界面。在镁合金基体和铝涂层液固复合过程中,镁合金液可以与氧化膜发生反应而破碎该氧化膜,实现界面间的润湿,形成冶金结合界面。③界面两侧的元素对基体与涂层的结合产生重要的影响。和纯铝基体相比,A356基体中Si、Mg元素降低界面间的润湿角和合金熔点,促进界面的冶金结合,并在界面形成一个过渡区域。AZ91熔液中Mg可与铝涂层表面氧化物反应,并进行相互扩散,在界面形成三个扩散层,实现冶金结合。④随着浇注温度的升高,涂层和基体的结合方式由机械结合逐渐转化为冶金结合。一方面,温度的升高有利于界面间的润湿,另一方面,升高温度可增加界面间液固复合的时间,促进界面间发生熔合和扩散作用。⑤对于机械结合界面,热处理难以改变其结合状态。对于冶金结合界面,热处理可使基体组织更加细小,涂层和基体组织过渡更加平缓,增加扩散区域宽度。⑥对冶金结合界面的组织和成分进行了观察分析。纯铝涂层存在大量的片层状氧化物,这些氧化物之间的组织与纯铝基体一致并连为一体。铝涂层与A356的结合界面出现一个过渡区域,该区域组织比较细小。铝涂层和AZ91界面出现三个扩散层,这三个扩散层分别为Al12Mg17+?(Mg)、Al12Mg17和Al3Mg2+氧化物。⑦涂层和基体的结合机制可分为三个过程:润湿、熔合和扩散、渗透。润湿是实现冶金结合的先决条件,涂层表面状态、元素、温度等因素将影响界面润湿角。熔合和扩散将决定界面过渡层的宽度,温度和界面元素是主要影响因素。涂层喷涂工艺影响涂层孔隙率,使金属液渗透到涂层中。
[Abstract]:Thermal spraying, as one of the most widely used technology in surface engineering, has the characteristics of flexible construction, strong practicability, wide application and high production efficiency. Wear resistance and other fields have been widely used. However, the bonding mode between thermal spraying coating and substrate is generally mechanical, and it is easy to spalling, which limits the application of thermal spraying technology, in order to improve the bonding strength between coating and substrate, In this paper, the metallurgical bonding between the substrate and the coating is realized by the technology of compound casting. Firstly, a coating is sprayed on the core surface by thermal spraying, and the molten metal is poured into the mold to realize the combination of the coating and the substrate. This method has changed the traditional thermal spraying process which has the product body first and then the spray coating, and provides a new way of thinking for the connection between the coating and the substrate. In this paper, by controlling the substrate material, the pretreatment, the casting process and the post treatment process, The results and conclusions obtained from the study of interface bonding are as follows: by solid-liquid composite casting, Al / Al / Al / A356 and Al/AZ91 composite castings with metallurgical bonding interface have been successfully prepared. The results show that the method is feasible and can be used in many kinds of materials, that is, the oxide film on the surface of aluminum coating has an important influence on the interface bonding. In the process of liquid / solid composite of aluminum substrate and aluminum coating, the oxide film will hinder the wetting between interfaces. The surface treatment of the coating will promote the formation of metallurgical bonding interface at the interface. In the process of liquid-solid composite of magnesium alloy substrate and aluminum coating, the magnesium alloy solution can react with the oxide film and break the oxide film. The wetting between the interfaces is realized, and the elements on both sides of the interface form the metallurgical bonding interface .3 have an important effect on the bonding between the substrate and the coating. Compared with the pure aluminum matrix, the Si-mg element in the matrix of A356 reduces the wetting angle between the interfaces and the melting point of the alloy. Promoting the metallurgical bonding of the interface, and forming a transition region. AZ91 in the interface, mg can react with the oxide on the surface of the aluminum coating and diffuse with each other, forming three diffusion layers at the interface, and realizing the metallurgical bonding .4 with the increase of pouring temperature. On the one hand, the increase of temperature is beneficial to the wetting of interface, on the other hand, increasing temperature can increase the time of liquid-solid recombination between interfaces. For mechanical bonding interface, heat treatment is difficult to change its bonding state. For metallurgical bonding interface, heat treatment can make the matrix microstructure finer and the transition between coating and matrix structure more smooth. The microstructure and composition of metallurgical bonding interface were observed and analyzed by increasing the width of diffusion zone. The microstructure of these oxides is consistent with that of pure aluminum substrate. There is a transition area between the interface of aluminum coating and A356, and the structure of the region is smaller. There are three diffusion layers at the interface between aluminum coating and AZ91. The three diffusion layers are Al12Mg17? The bonding mechanism of Al 12 mg 17 and Al3Mg2 oxide 7. 7 coatings and matrix can be divided into three processes: wetting, fusion and diffusion, permeation. Wetting is a prerequisite for metallurgical bonding. Temperature and other factors will affect the wetting angle of the interface. The width of the interfacial transition layer will be determined by fusion and diffusion, and the temperature and interface elements are the main factors. The coating spray process affects the porosity of the coating and makes the liquid metal permeate into the coating.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

【相似文献】