【作者】 杨清；

【导师】 赵宇光；

【作者基本信息】 吉林大学 ， 材料加工工程， 2013， 硕士

【摘要】 轴承作为机械设备中重要的支撑部件,随着工作环境的复杂化,对其性能及寿命提出了更加严格的要求。GCr15钢作为滚动轴承的制造用钢,严重地影响轴承工作时的使用寿命,所以提高轴承的使用寿命势必要提高GCr15钢的性能。电脉冲处理作为近几年来发展的新兴技术,由于显著影响材料的组织与性能而被人们越来越多的关注。本论文是以GCr15钢作为基本研究对象,研究了瞬时高能量脉冲电流处理对其组织和性能的影响。研究发现,不同的脉冲电流参数以及冷却条件对GCr15钢的显微组织以及力学性能都有不同的影响。随着脉冲电流密度的增加或作用时间的延长,GCr15钢的组织由珠光体转变为马氏体,力学性能也随之提高,但是随着脉冲电流或作用时间的继续增加,由于过高的温度导致晶粒长大组织粗化,其力学性能也随之下降。在水冷条件下GCr15钢的马氏体组织要比油冷的组织细小,但是由于水冷冷速过快出现微裂纹,所以水冷的力学性能要比油冷的差。与传统热处理相比,经过优化参数的脉冲电流处理后,GCr15钢的抗拉强度提高了3%,延伸率提高了31.1%,并且它的耐磨性也相应提高。对于不同初始状态的GCr15钢,经过脉冲电流处理后,组织均发生马氏体转变,但是马氏体组织的细化程度不同,同时在基体中的碳化物也是以不同形态析出的,这就导致脉冲电流处理后不同初始状态的力学性能出现差异。结果表明,预处理的碳化物颗粒越细小越弥散,它的综合力学性能越好。经过脉冲电流处理后的GCr15钢,不同的后续处理也会使得显微组织与力学性能发生变化,其中经过二次小参数的脉冲电流处理后效果与回火处理相近,因此可以取代回火处理。对于GCr15钢脉冲电流表面处理,由于软硬相的有机结合,其耐磨性要比传统热处理的好,但是不同电极形状对GCr15钢耐磨性影响也不相同,矩形电极由于在处理区的尖端处产生应力集中,形成拉应力,而且不同方向的强化效果也不同,因此矩形电极处理后的耐磨性要比球形电极处理的差。通过这些理论研究可以为GCr15钢的脉冲电流处理在工程实践中的应用奠定基础。更多还原

【Abstract】 Bearing is an important support component in mechanical equipment. With applicationenvironment complicating, Bearing’s performance and life have been required more andmore severely. As rolling bearing manufacturing steel, GCr15steel seriously affected thelife of bearing, so increment of bearing life depends on the performance of GCr15steel.Since electropulsing has been regarded as a new technology to evidently influence materialmicrostructure and performance in recent years, it has caused more and more attention bypeople. In this paper, the studies focus on the influence of microstructure and mechanicalproperties for GCr15bearing steel by electropulsing.The research found that different electropulsing parameters and cooling conditionshave different effects on the microstructure and mechanical properties of GCr15steel. Asthe pulse current density or the duration of action increased, microstructure of GCr15steeltransforms from pearlite to martensite and mechanical properties also improve. However,with the pulse current continuously increasing, excessive heat leads to microstructurecoarsening and grain growth, therefore it’s mechanical properties decrease. Although themartensite for GCr15steel in the water-cooled condition is finer and smaller than in theoil-cooled condition, the mechanical properties in water-cooled condition is poorer than inoil-cooled condition due to the fast water cold speed forming micro-cracks. Compared withconventional heat treatment, the tensile strength and elongation increased to3%and31.3%respectively by electropulsing treatment of optimized parameters. And wear resistance alsois correspondingly improved.For GCr15steel of different initial state, the degrees of martensite refinement isdifferent, but also the carbide particles are in the different forms of precipitating in thematrix. These lead the mechanical properties of the different initial state to have differenceby electropulsing. The results show that, the finer and more diffused carbide particles of pre-treatment are, the better mechanical properties are.Meanwhile different post-treatment after electropulsing also makes microstructure andperformance change. As the effect of the secondary electropulsing treatment of smallparameters is similar to tempering treatment, it can replace tempering treatment. For GCr15steel electropulsing surface treatment, it is found that due to organic combination of hardand soft phase the wear resistance is better than traditional heat treatment. However,different electrode shape has not same influence on GCr15steel wear resistance. Forrectangular electrode, the tip treatment zone is emerged of stress concentration and tensilestress, and the strengthening effect in different directions is also different. Therefore thewear resistance after rectangular electrode treatment is poorer than spherical electrodetreatment. This laid a foundation for the further research about GCr15steel’s engineeringapplication after electropulsing treatment.更多还原