【作者】 朱军；

【导师】 黄因慧；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2007， 硕士

【摘要】 纳米晶沉积层与纳米材料一样,具有与传统材料不同的物理化学性能,而受到研究人员的关注。本文在探讨了纳米晶沉积层的制备技术,复合沉积层的应用与发展,电沉积原理及其相关研究现状后,提出了在喷射电沉积(简称喷镀)的基础上,结合脉冲电沉积的优势,制备纳米晶镍沉积层及其复合沉积层的方法,并引入激光重熔工艺,细化沉积层晶粒,提高沉积层的致密性,所完成的主要工作有:(1)自行设计、组装一套喷镀试验系统,使用传统瓦特镀液在脉冲电源的作用下在不锈钢和45钢基材表面上喷镀纳米晶镍沉积层,再激光扫描喷沉积层以获得激光重熔纳米晶镍沉积层。(2)本文研究了脉冲参数(占空比、频率、平均电流密度)对沉积层表面显微硬度的影响,并通过正交试验对工艺参数进行优化。结果表明,最佳脉冲工艺参数为:脉冲频率1000HZ、占空比20%、平均电流密度为39.8 A/dm~2,此时沉积层表面显微硬度最高(530.6HV)。(3)采用现代分析手段(SEM、XRD),对制备的喷镀纳米晶镍沉积层表面的外观形貌特征和微观组织结构进行观察。分析表明:在本试验条件下,电流密度为39.8A/dm2时,电沉积速率较快,而且复合沉积层表面质量较好。与直流相比,采用脉冲电流沉积能明显细化沉积层晶粒,并能在较高的峰值电流密度下获得纳米晶沉积层。对纳米晶镍沉积层激光重熔后,发现沉积层熔融区内的晶粒尺寸明显减小。通过XRD观察发现沉积层表现出明显的沿晶面(111)择优取向。(4)利用测试设备对沉积层的性能进行测试分析,激光重熔后试件在显微硬度、抗拉伸性能和耐腐蚀性能与喷镀纳米晶镍沉积层相比均有所提高。更多还原

【Abstract】 Nanocrystalline coatings get more and more attention same as nano-materials because of owning many special physical and chemical quality compared as traditional materials. In this paper, the nanocrystalline coating preparation method, nano compound coatings application and development, electroplating theory and its current research situation are discussed. The preparation of nanocrystalline nickel coating and compound coatings is introduced, which based on jet electrodeposition(Simplified as JED), and combined with the advantage of pulse electrodeposition. Strengthen process on coating by laser remelting is introduced, because of the disadvantage of combination intensity between JED coating and substrate. Choose propriety remelting process parameters, which diminished the surface crystal, increased the coating’s compact quality, improved the combination between coatings and the base metal, and implemented the transformation form mechanism combination to metallurgy combination. The major conclusions gotten in this dissertation are presented as follows:(1) Design and assembly a jet electrodeposition system. Deposited the nanocrystalline nickel coating on the base metal(SUS304L and 45 Steel) using direct and pulse supply, and watts plating bath, then laser remelting the coating, got the laser remelted nanocrystalline nickel coating.(2) Research on the effect of pulse electrodeposition process parameters including duty ratio, frequency, current intensity, on the microhardness of nanocrystalline nickel coating. The process parameter was optimized by orthogonal method. Reaults showed that the optimum process parameters to obtain nanocrystalline nickel coating by pulse plating process are as follows: duty ratio of 20%, frequency of 1000HZ, current intensity of 39.8 A/dm~2, the microhardness of nanocrystalline nickel coating is the best (530.6HV).(3) Observed the surface morphology and microstructure of nanocrystalline nickel coating by SEM and XRD. SEM results of this experiment show that the current density has huge influence to the nanocrystalline nickel coating, the electrodeposition speed was rapid and the coating quality was good at the current intensity of 39.8 A/dm2. The size of crystal are decreased more on the pulse condition, compared as the direct current, and the coating’s size of crystal are obviously diminished on the remelted district when the nanocrystalline nickle coating was strengthening processed by laser remelting. XRD results show that the nanocrystalline nickel coating is preferred orientation of (111).(4) Research on the coating’s mechanism performance by testing equipment. Results showed: The size of crystal of anocrystalline nickel coating are diminished after laser remelting, and the coating’s microhardness, the strain-stress characteristic and the corrosion resistance obviously increased.更多还原