熔碳强化单元体对U71Mn钢疲劳磨损性能的影响

发布时间：2018-06-14 17:02

本文选题：激光熔碳 + 耦合仿生　；参考：《吉林大学》2017年硕士论文

【摘要】：铁路钢轨作为铁路运输中重要的组成部件,其质量和性能直接影响铁路运输的安全和效率。随着我国客运高铁的飞速发展和货运铁路运输量的逐渐提高,铁路钢轨的疲劳磨损日益严重,导致了其服役时间逐渐缩短。为了保证铁路运输的行车安全,并尽量降低铁路运营的成本,我们需要尽可能地提高铁路钢轨的抗滚动疲劳磨损性能,延长其服役时间。根据以往的研究,通过激光仿生熔凝技术在基体材料表面制备出高硬度的仿生单元体,高硬度的单元体和低硬度的基体材料形成一种类似于生物体表的软硬相间的耦合仿生结构,能有效提升基体材料表面抗滚动疲劳磨损性能。如果进一步提高仿生单元体的硬度,有可能进一步提高表面抗滚动疲劳磨损性能。本文采用激光熔碳的方式对U71Mn钢进行处理,制备比熔凝单元体硬度更高的熔碳单元体,使其在滚动磨损中承受更大的应力,从而进一步提高仿生试样表面的抗滚动疲劳磨损性能。研究表明:经过激光加工处理的仿生试样比未处理试样具有优异的抗滚动疲劳磨损性能。相比于激光熔凝处理的仿生试样,激光熔碳处理的仿生试样具有更好的抗滚动疲劳磨损性能。根据对生物模型的简化并再设计,可发现激光熔碳处理的具有网格状单元体的仿生试样抗磨损性能最佳,其磨损失重量相比于未处理试样降低了82%。由于激光熔碳处理,外部的碳元素进入到单元体内,使得单元体整体碳含量提升,从而造成晶格畸变。相比于熔凝单元体,熔碳单元体内碳含量高,易形成高碳马氏体组织,使其显微硬度更高,抗塑性变形能力更强,得到了进一步强化。在磨损实验中,高硬度的熔碳单元体能够承受更多的应力,使得基体部分所承受的应力减少,提升磨损试样的抗滚动疲劳磨损性能。当涂覆碳层厚度不变,激光参数逐步增大时,仿生试样的抗滚动疲劳磨损性能将会出现抛物线式的变化;同时,涂覆碳层厚度的减小会导致使用相同激光参数处理试样的抗滚动疲劳磨损性能得到提高。
[Abstract]:As an important component of railway transportation, rail quality and performance directly affect the safety and efficiency of railway transportation. With the rapid development of China's passenger high-speed rail and the gradual improvement of freight rail transport volume, the fatigue wear of railway rail is becoming more and more serious, which results in the shortening of service time. In order to ensure the safety of railway transportation and reduce the cost of railway operation as far as possible, we need to improve the rolling fatigue wear resistance of railway rail as much as possible and prolong its service time. Based on previous studies, a high hardness bionic unit was fabricated on the surface of the substrate by laser bionic solidification. The high hardness unit and the low hardness matrix form a kind of coupling bionic structure similar to the biological table, which can effectively improve the rolling fatigue wear resistance of the substrate surface. If the hardness of the biomimetic unit is further improved, the rolling fatigue wear resistance of the surface may be further improved. In this paper, the U71Mn steel was treated by laser melting carbon, and the melting carbon unit with higher hardness than the melting unit was prepared, which made it bear more stress in rolling wear. Thus, the rolling fatigue wear resistance of the biomimetic specimen surface is further improved. The results show that the biomimetic specimen processed by laser has better rolling fatigue wear resistance than the untreated sample. Compared with the biomimetic specimen treated by laser melting, the bionic specimen treated by laser melting carbon has better rolling fatigue wear resistance. According to the simplification and redesign of the biological model, it can be found that the biomimetic specimen with grid element treated by laser melting carbon has the best wear resistance, and its wear loss weight is reduced by 82% compared with the untreated sample. As a result of laser carbon melting, the external carbon elements enter into the unit, which makes the whole carbon content of the unit increase, resulting in lattice distortion. Compared with the melting unit, the carbon content in the carbon melting unit is high, and the high carbon martensite structure is easy to form, which makes it have higher microhardness and stronger resistance to plastic deformation, which has been further strengthened. In the wear test, the high hardness carbon melting unit can withstand more stress, which can reduce the stress of the matrix and improve the rolling fatigue wear resistance of the wear specimen. When the thickness of the coated carbon layer is constant and the laser parameters increase gradually, the rolling fatigue wear resistance of the biomimetic specimen will be changed in a parabolic manner. The decrease of the thickness of the coated carbon layer will improve the rolling fatigue wear resistance of the samples treated with the same laser parameters.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4;TG142.12

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