磁化—激光熔覆复合技术强化与修复零部件表面性能的研究

发布时间：2018-03-18 08:31

本文选题：激光熔覆　切入点：磁化处理　出处：《江西理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：激光熔覆技术不仅可强化机械零件的表面,还可对表面失效的零部件进行修复,所以该技术在工业中的作用将会愈来愈明显。其显著特点是在不影响基材的整体使用性能的同时还提高了需要强化与修复区域的表面性能,甚至还赋予它新的性能。但是铁基涂层存在开裂、氧化、气孔等缺陷使得该项技术的发展受到制约。随着磁场辅助技术在各个技术复合应用中卓见成效,且磁场磁化技术操作简单,绿色无污染。因此,本文主要是应用激光熔覆基础上结合磁化的复合技术,研究此复合技术是否能够起到强化覆层以及修复零部件表面性能的效果。本文选用常用的45钢作为基体材料,经调质处理后,利用自制的磁化装置对其预先磁化处理,首先研究了磁化对基体材料摩擦学性能和组织的影响;其次,探讨了不同熔覆工艺参数的组合下所获得涂层宏观质量和性能的优异,以获得该实验条件下的最佳激光工艺参数;在获得激光工艺参数后,再重新对基体磁化,然后在其表面部位激光熔覆铁基涂层进行实验研究,探索预先磁化基材对覆层摩擦学性能以及组织产生的影响。实验研究结果表明:虽然经磁化处理后,基体的表面硬度并未有所提高,且磁化频率过高过低时,其硬度反而会有小幅的下降,但是所有经过磁化处理后的基材试样的耐磨性却优于未磁化的;同时,磁化还降低了摩擦系数,细化了基材组织。工艺参数对比试验表明熔覆层成形质量的优劣主要取决于扫描速度的快慢,而后是激光功率的大小;只有在参数组合较好的情况下,得到的涂层可见气孔少,成形质量和耐磨性也较好。磁化-激光熔覆复合实验结果表明基体经过磁化处理后的涂层硬度要略高于未磁化的,耐磨性也有明显的改善,晶粒组织得到了进一步的细化,硬质颗粒分布也更均匀。单独磁化基体和磁化-激光熔覆复合的实验结果都表明,磁化频率为25Hz的磁化效果最好,可认为25Hz是本实验条件下的最佳磁化频率。通过Matlab软件,根据w-m分形函数模型进行了二维轮廓曲线和三维轮廓曲面的模拟,探讨了轮廓形貌复杂程度与分形参数的关系,二维模拟结果表明分形维数和特征尺度系数是其主要影响参数,随分形维数由1.3变化到1.9,模拟表面轮廓曲线越来越趋于复杂,即曲线形状和幅值都在变化。对于三维轮廓曲面而言,随分形维数由2.1增大2.9,所获得表面轮廓形貌也越来越趋于复杂,模拟后的图形表明分形维数仍然是影响表面轮廓曲面形貌的主要参数。
[Abstract]:Laser cladding technology can not only strengthen the surface of mechanical parts, but also repair the surface failure parts. So the role of this technology in industry will become more and more obvious. Its remarkable feature is that it improves the surface properties of the areas that need to be strengthened and repaired while not affecting the overall performance of the substrate. It has even been given new properties, but the development of the technology has been constrained by the defects of the Fe-based coating such as cracking, oxidation, porosity and so on. The magnetic field magnetization technology is easy to operate and green without pollution. Therefore, this paper mainly uses the laser cladding technology combined with magnetization technology. This paper studies whether the composite technology can strengthen the coating and repair the surface properties of the parts. In this paper, 45 steel is used as the substrate material. After the tempering and tempering, the premagnetized steel can be premagnetized by the self-made magnetization device. Firstly, the effect of magnetization on the tribological properties and microstructure of the substrate is studied. Secondly, the excellent macroscopical quality and properties of the coatings obtained by the combination of different cladding process parameters are discussed in order to obtain the best laser processing parameters under the experimental conditions. After obtaining the laser process parameters, the substrate was magnetized again, and then laser cladding the iron-base coating on the surface of the substrate was studied experimentally. The effect of premagnetized substrate on the tribological properties and microstructure of the coating was explored. The experimental results showed that the surface hardness of the substrate did not increase after magnetization, and the frequency of magnetization was too high and too low. The hardness decreases slightly, but the wear resistance of all magnetized substrate samples is better than that of unmagnetized ones, and the coefficient of friction is reduced by magnetization. The microstructure of the substrate was refined. The comparison test of process parameters showed that the quality of the cladding coating was mainly determined by the speed of scanning and the laser power, and only when the parameters were well combined, the visible porosity of the coating was less. The results of the magnetization and laser cladding experiments show that the hardness of the coating after magnetization is slightly higher than that of the unmagnetized coating, and the wear resistance is obviously improved, and the grain structure is further refined. The results of the experiments of magnetization matrix alone and magnetization laser cladding show that the magnetization frequency of 25Hz is the best, and that 25Hz is the best magnetization frequency under the condition of this experiment. According to w-m fractal function model, the two-dimensional contour curve and three-dimensional contour surface are simulated, and the relationship between the profile complexity and fractal parameters is discussed. The results show that fractal dimension and characteristic scale coefficient are the main influencing parameters. With the change of fractal dimension from 1.3 to 1.9, the simulated surface contour curve becomes more and more complex, that is, the shape and amplitude of the curve are changing. With the increase of fractal dimension from 2.1 to 2.9, the surface contour morphology becomes more and more complex. The simulated figure shows that fractal dimension is still the main parameter affecting the surface contour surface morphology.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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