【作者】 蒋斌；

【导师】 丁培道； 徐滨士；

【作者基本信息】 重庆大学 ， 材料学， 2003， 博士

【摘要】 电刷镀技术从普通电刷镀、复合电刷镀到纳米颗粒复合电刷镀的发展，是为了使装备零件满足在高速、重载等恶劣工况下的服役要求。采用纳米颗粒复合电刷镀技术的目的是为了制备具有优良耐磨性能的纳米颗粒复合电刷镀层。 本文采用多种方法(超声波、机械、表面活性剂和高能机械化学法等)制备纳米颗粒复合电刷镀液，通过沉降试验优化镀液制备工艺并测试纳米颗粒在复合镀液中的粒度分布、Zeta电位以及复合镀液的pH值和电导率等特性。采用透射电子显微镜(TEM)结合扫描电子显微镜(SEM)、能谱仪(EDS)等分析手段研究纳米颗粒复合电刷镀层的微观结构和组织形貌，研究纳米颗粒复合电刷镀层的沉积机理及纳米颗粒对镀层的强化机理，还对纳米颗粒在复合镀层接触疲劳过程中的行为、从室温到500℃的微动磨损特性及抗微动磨损机理进行了研究。获得的主要成果如下： 提出了一种能有效地制备性能稳定的纳米颗粒复合电刷镀液的方法——高能机械化学方法。与普通超声波方法、机械方法和一般表面活性剂方法相比，高能机械化学方法能降低纳米颗粒的表面能，纳米颗粒在镍基镀液中充分润湿，其表面形成总体上带负电的双电层，产生较大的静电位阻作用；加入的活性剂同时又起到空间位阻的作用。静电位阻和空间位阻的协同作用使纳米颗粒在镀液中不易团聚，分散均匀，并使复合镀液的性能长期稳定。 优化了镀层制备工艺以及纳米颗粒在镀液中的添加量。当镀液中纳米颗粒含量为20g/L时，并采用高能机械化学法制备，采用一次活化工艺作为施镀工艺，可以得到镀层中纳米颗粒含量为1.5～3.5ω％(质量百分数)、组织均匀、纳米颗粒分布均匀的复合电刷镀层。复合镀层的显微硬度在600～700Hv范围内，最高达到692Hv，是普通快镍镀层的1.58倍。 用SEM和TEM观察了纳米颗粒复合电刷镀层的组织结构，探讨了纳米颗粒复合电刷镀层的强化机理，即：细晶强化、高密度位错强化和第二相质点强化。复合镀层表面形貌细腻平整，断面组织细小，镀层中基质金属镍晶粒细小。镀层中含有大量的位错和孪晶等晶体缺陷。纳米颗粒呈弥散分布，与基质金属结合紧密。指出了纳米颗粒复合电刷镀工艺对纳米颗粒粒径存在选择性，只有粒径小于或接近一次沉积厚度的纳米颗粒才能有效地与金属离子共沉积。 对纳米颗粒复合电刷镀层断面组织和表面形貌的分析，阐明了纳米颗粒复合电刷镀层的生长过程分为三个阶段：均匀生长阶段、微凸体形成阶段及树枝状单元形成阶段。复合镀液中纳米颗粒的Zeta电位值均小于零，证明纳米颗粒与基质重庆大学博士学位论文金属的共沉积机理是以力学机理为主。 首次对纳米颗粒复合电刷镀层接触疲劳变形层进行了TEM观察，表明在接触疲劳失效过程中，弥散分布的纳米颗粒通过阻碍位错的滑移来阻碍塑性变形的发生，并对复合镀层起到硬质强化作用，抑制疲劳裂纹的萌生和扩展，揭示了纳米颗粒复合电刷镀层具有优良抗接触疲劳性能的本质。复合镀层的接触疲劳寿命可超过100万次，显著高于普通快镍镀层。纳米颗粒复合电刷镀层的接触疲劳失效过程研究表明，该过程由裂纹萌生、裂纹扩展及镀层最后断裂三个阶段组成。 对纳米颗粒复合电刷镀层组织与抗微动磨损性能关系的研究阐明了纳米颗粒复合电刷镀层的抗微动磨损机理。纳米颗粒复合电刷镀层细腻的表面形貌、细小的组织结构、高硬度和弥散分布的纳米颗粒以及微动磨损过程中纳米颗粒对磨屑层的再强化，提高复合镀层磨损面的塑性变形抗力，降低材料的粘着和转移，抑制裂纹萌生和扩展，使纳米颗粒复合电刷镀层具有较高的抗微动磨损性能。 研究证明，采用高能机械化学方法对纳米颗粒与镍基电刷镀液的多相多离子体系处理后，能制备出性能稳定的纳米颗粒复合电刷镀液，并能通过优化的电刷镀工艺制备出组织结构细小均匀的纳米颗粒复合电刷镀层。纳米颗粒复合电刷镀层具有比普通快速镍镀层更加优良的抗接触疲劳性能和微动磨损性能。纳米颗粒复合电刷镀技术提升了传统电刷镀技术，在装备再制造工程中提高零件表面的综合性能方面显示出巨大的作用并产生了显著的经济效益。 本文主要实验研究工作在装甲兵工程学院装备再制造技术国防科技重点实验室完成。受到了国家973计划项目(材料的环境行为与失效机理)子课题(材料失效过程的基础研究和损伤控制方法，编号:G1999065009)、总装维修改革项目 (编号:200lZB06)、2002年中英政府科技合作项目(编号:2002M3)以及装甲兵工程学院装备再制造技术国防科技重点实验室基金的资助。更多还原

【Abstract】 To make the equipments meet the severe service requirement, the electro-brush plating technology has been developed from the single coating, to the composite coating, and to the nano-particle composite coating. The nano-particle composite electro-brush plating technology is used for preparing the composite coating with the distinctive anti-wear performance.Nano-particles were dispersed into the nickel brush-plating electrolyte by using ultrasonic, mechanical, surfactant and high energy mechanical and chemical techniques, for the purpose of preparing the nano-particle composite electro-brush electrolyte. Characteristics of the nano-particles in the composite elctrolytes such as size distribution and Zeta potential were tested as well as that of composite electrolytes such as pH value and conductance. Microstructure of nano-particle composite coatings was studied through TEM, SEM and EDS, and deposition mechanism of the composite coatings was investigated as well as their reinforcement mechanism. Contact fatigue resistance of composite coatings was studied as well as anti-fretting wear from room temperature to 500℃. The main results gained are as follows:A high energy mechanical and chemical technique was obtained which could effectively prepare nano-particle composite electrolytes based on the nickel electrolyte. Comparing with the general ultrasonic, mechanical and surfactant techniques, the high energy mechanical and chemical technique could reduce the surface energy of nano-particles and cause them to be soaked by the electrolyte. So a double electricity film was formed on the surface of nano-particles, taking on electronegative as a whole and could play a role as the static potential obstruction, and meanwhile the surfactant could play a role as the space obstruction. Therefore, conglomeration of nano-particles was in a light degree, uniformly dispersed in the composite electrolyte and properties of the composite electrolyte were steady for a long time.The preparation process of the composite coatings was optimized as well as the nano-particle content in the electrolyte. When the composite coatings were prepared by one-step activation process and from the electrolyte with the 20 g/L nano-particles content prepared by the high energy mechanical and chemical technique, the composite coatings had uniform microstructure and the nano-particle content of 1.5-3.5%. The nano-particles evenly dispersed in the coatings and adhere compactly to the nickelmatrix Micro-hardness of the composite coatings could reach to 700 Hv, over 1.5 times of that of the nickel coating.Micro-structure of nano-particles composite coatings was analyzed by means of SEM and TEM. Reinforcement mechanisms of composite coatings were as follows: fine crystals, high density dislocations and second phase particles. Nickel crystal grains in the composite coating were about at the size of 50 nm and the surface morphology of the coatings was fine, compact and smooth, and their structure was layer-like which thickness was about 50 nm. There were large amounts of dislocations and twin grains in the composite coating. The distribution of nano-particles was uniform and no agglomeration, and also the nano-particles adhered to nickel compactly. The nano-particle composite electro-brush plating deposited selectively the nano-particles which size were less than the thickness of the monolayer and therefore made the size of nano-particles in the coatings smaller.By analyzing the cross-section microstructure and surface morphology of composite coatings, it was elucidated that the deposition process of composite coatings was formed by continuous three stages as following: uniform growth, formation of little convex body and formation of dentritic crystals. According to the denotation of Zeta potential of the surface of nano-particles, it was clear that the co-deposition mechanism of nano-particles with nickel was mainly mechanics.Micro-structure of the contact fatigue deformation layer showed that in the process of contact fatigue, nano-pa更多还原