【作者】 王玮琳；

【导师】 田宗军；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2006， 硕士

【摘要】 由于纳米材料具有与传统材料不同的独特性能,而倍受关注。本文在分析纳米晶材料的优异性能的基础上,采用直流和脉冲喷射电镀方法制备了纳米晶镍镀层,再针对喷射镀层的不足,对镀层进行激光重熔,通过选择优化的重熔工艺参数,细化镀层晶粒,提高镀层的致密性,增强镀层与金属基体的结合强度。所完成的主要工作有:1.利用喷射电镀试验系统,使用watts镀液在直流和脉冲电源的作用下在基材表面上喷镀纳米晶镍镀层,再采用激光扫描喷镀层以获得激光重熔喷射纳米晶镍镀层。2.采用现代分析手段,对制备的喷射纳米晶镍镀层的微观组织结构进行了详细分析。分析表明:电流密度对喷射纳米晶镍层表面形貌有很大的影响,晶粒大小随电流密度的变化趋势是先降后升;与直流相比,采用脉冲电流沉积能明显细化镀层晶粒,并能在较高的峰值电流密度下获得纳米晶镀层。对纳米晶镍镀层激光重熔后,发现镀层熔融区内的晶粒尺寸明显减小。3.利用测试设备对镀层的机械性能进行测试分析。激光重熔后的镀层显微硬度明显提高,而拉伸性能和耐腐蚀性能与喷射纳米晶镍镀层相比则有所下降。结果表明:激光重熔后试样出现较多的微观缺陷且在基体内部有较大面积的软化区存在,从而导致试件的拉伸性能下降以及腐蚀液渗入加速。4.将试验的分析结果与数值模拟温度场模型进行比较,验证试验结果与模型计算结果基本相符,并根据温度场模型进一步优化相关的试验参数。更多还原

【Abstract】 Nano-materials get more and more attention because its have many special quality compared as traditional materials.In this paper, the nanocrystalline nickel coating whose electrical source inevitably are direct and pulse current was made by jet electroforming, then remelted the coating in order to eliminate the limitations. 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 got in this dissertation are presented as follows:1. Deposited the nanocrystalline nickel coating on the base metal by jet electroforming system, direct and pulse supply, and watts deposition liquid, then laser remelted the coating, got the laser remelted nanocrystalline nickel coating by jet electroforming.2. Analyzed the coating’s microstructure by modern analysis methods,. And the analysis showed: electric current density have huge influence to the nanocrystalline nickel coating at direct current, the change trend about the size of crystal is increased d firstly decreased then; on the pulse condition, the coating’s size of crystal are obviously diminished, and the nanocrystalline coating can be get on the higher electric current density; after laser remelted, the coating’s size of crystal are obviously diminished on the remelted district.3. Analyzed the coating’s mechanism performance by testing equipment. Founded out: the coating’s microhardness profiles obviously increased but the strain-stress characterization and the corrosion resistance have a little of decrease compared as the coating only jet electroforming. The main cause are that there are many cracks in the remelted coating and the soft district plentyly exist in the base metal which made the mechanism performance decreased and corrosive liquid filtering increased.4. Compared with the analyzing result and the mathematics model’s calculation result. The calculation result was basic consistent of the analyzing result and got a series of laser process optimize parameter.更多还原