【作者】 白永兰；

【导师】 李伟善； 黄启明；

【作者基本信息】 华南师范大学 ， 物理化学， 2004， 硕士

【摘要】 ABS塑料具有质轻、可塑性好、表面细致、光滑等特点，并可以根据需要制成不同形状，但存在硬度低、不耐磨等缺点，限制了其应用。复合电镀是在普通电镀基础上，通过加入高硬度、高耐磨性的复合粒子发展起来的一种表面处理技术。对ABS进行复合电镀可以大大提高镀层的硬度及耐磨性，扩展ABS塑料的应用范围，延长材料的使用寿命。 本文采用大粒度SiC颗粒为分散粒子，以Ni为基质金属，以ABS塑料为基体，先后采用粗化、敏化、活化(离子型活化和胶态钯活化)、化学镀铜、化学镀镍、电镀(铜、镍)、复合电镀(Ni-SiC)、霍尔槽实验、磨擦实验等多种实验方法，筛选出在ABS塑料磨头上电镀Ni—SiC复合镀层的新工艺，将塑料电镀与复合电镀有机结合起来，将塑料的质轻、易加工和SiC微粒的高硬度、强磨削力结合起来，获得的复合镀层结合力好，硬度高，耐磨性强。 通过对每一道工序的系统研究和实验，并综合考虑经济技术可行性和易操作性，确定了较佳的工艺流程和工艺规范。 (1) 通过反复实验，确定工艺流程：首先通过粗化、敏化、活化和化学镀铜，使塑料表面金属化，再电镀铜加厚铜镀层，增强后续镀层与塑料基体的结合力，然后预镀镍，最后电镀Ni—SiC复合镀层。 (2) 对于常用的各种活化工艺进行实验，综合考虑成本和可操作性，确定活化采用硝酸银离子型活化液。 (3) 在塑料表面金属化方面，对化学镀铜和化学镀镍都进行了系统的实验，并分别探讨了镀液配方及化学镀工艺条件对稳定性和镀速的影响。根据实验结果和所用试样的材料，最终选择化学镀铜进行塑料电镀前处理。 (4) 根据挂具设计的基本原则以及实验所用塑料零件的实际形状设计摘要 了电镀挂具，并利用现有设备进行改造进行Ni一siC复合镀。(5)对所得镀层的性能进行了检测，镀层中SIC粒子含量为20.11 (Vol%)且均匀致密;镀层的硬度和耐磨性分别提高到纯镍镀层 的2.68倍和4.1倍;结合力实验也表明镀层与基体具有良好的结 合力。此外，也提出了工艺中值得注意的几个问题。(l)粗化要适度。粗化不足和粗化过度都会降低镀层结合力，粗化不 足还易显露塑料基体，粗化过度，塑料易产生裂纹。(2)电镀铜时铜镀层必须具有一定的厚度，不应低于5林m，防止镀镍 后镀层起皱，从而影响镀层与基体的结合力。(3)电镀时镍阳极必须使用阳极套，并要经常清洗阳极泥，防止阳极 泥转移到磨头表面产生镍瘤。(4)Ni一siC复合电镀宜使用较低的电流密度。由于siC微粒不导电， 磨头实际被镀覆的表面积低于宏观表面积。若电流密度过大，超 过所允许的上限值，会析出大量的氢气，可能冲散表面覆盖的siC 微粒，而且易使磨头表面镀液PH值急剧上升而形成氢氧化镍沉 淀，导致镀层质量恶化。(5)镀层厚度应与siC微粒粒度相当。既要使微粒牢固地固定在镀层 中，又要防止镀层过份包裹微粒，使失去磨削作用。更多还原

【Abstract】 ABS Plastics is light, plastic and smooth-skined. It can be made to different shapes. However, the applications of ABS plastics is limited due to its low-hardness and bad wear-resistance. Based on the ordinary electro-plating, composite plating has been developed as a new surface-treatment technology by adding high-hardness, high wear-resistant particles during plating. The hardness and the wear-resistance of ABS are evidently improved, and its serviceable life is prolonged by composite plating. Therefore, the application of ABS is expanded by composite plating..A novel process of Ni-SiC composite plating on ABS plastics grinding head was developed in this paper. Several methods including chemical coarsing, metal ion absorption, activated process, electroless plating, electroplating, composite plating, Hull cell, friction test, etc. are used. Large SiC particles were used as disperse medium, Ni as host metal, and ABS plastics as matrix. Lightweight and easy machinability of plastics were combined with high hardness and abrasion resistance of SiC particle in this process. The composite plating had good adhesion, high hardness and outstanding wear resistance.The best conditions for composite plating had been obtained by investigating in detail every working procedure. Economy and easy-to-operate were also considered.(1) First, Metallizing ABS plastics surface by chemical coarsing, metal ion absorption, metal ion reducing and chemical copper-plating. Then, the copper-coating was thickened by electroplating in order to improve adhesion between following-coating and plastics matrix, and nickel was preplating. Finally, Ni-SiC composite was plated.(2) By test various activated processes. Silver nitrate ionic activated process was choosed for its low cost and convenience.(3) Electroless copper plating was compared with electroless nickel plating about the metallizing technique of plastics surface. Influences of the component of plating solution and the chemical plating technology on stability and deposition rate of electroless plating were studied. It was found that electroless copper plating was better than electroless nickel plating.(4) A new rack was developed according to the principle of rack designing and actual shape of the plastics part. The equipment available was reformed for Ni-SiC composite plating.(5) SiC content in coating was 20.11(Vol%). Coating was fine and close. The hardness was 2.68 times pure Ni coating, and wear-resistance was 4.1 times pure Ni coating. The adhesion between the composite coating and the matrix was fine.In addition, there were several points should be mentioned in the proposed process.(1) Chemical coarsing should be moderate. The adhesion of coating would be depressed by both under-coarsing and over-coarsing. The plastics matrix might be exposed with under-coarsing. The cracks might appear on the coating with over-coarsing.(2) The thickness of copper coating should be over 5m for preventing coating wrinkle.(3) Anode envelope should be used during electroplating. Anode slime should be cleaned frequently in order to prevent Ni particle deposition on the plastics grinding head.(4) Low current density is better for Ni-SiC composite plating, the SiC particles is nonconductive. So the real surface area of the plastics grinding head is much less than the apparent area. Liberation of hydrogen gas would be increased rapidly and SiC particles on the surface might be dispersed if the current density exceed the upper limit. Furthermore, nickelous hydroxide wouldbe deposited because the pH of plating solution nearby the surface rapidly increased. All of above might result in coating deterioration.(5) The thickness of coating should be suitable with the size of SiC particles. On the one hand, the particles must be fixed on the coating. On the other hand, the grinding ability of the composite plating would be red更多还原