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45钢激光仿生强化工艺及性能研究

发布时间:2018-10-20 12:42
【摘要】:磨损、断裂是引起金属零部件失效的主要原因,且这些失效形式往往发生于材料表面,故提高金属零部件的表面性能,延长其使用寿命,具有重要的理论意义和实用价值。本文以工业中被广泛使用的45钢为试验材料,首先通过正交试验方法研究了离焦量、电流、扫描速度等工艺参数对淬火层硬度的影响,优化了激光淬火工艺。然后在仿生学研究的基础上,以叶片、土鳖虫鞘翅、蜻蜓翅膀、贝壳、蜥蜴角质鳞片等具有良好耐磨性或抵抗断裂能力的生物体表作为设计原型,设计并制备了激光仿生强化单元体,并研究了各种激光仿生强化单元体的磨损性能和拉伸性能。结果表明:1.影响淬火层硬度的主要因素是离焦量,其次是电流;最佳的激光淬火工艺参数为离焦量22.5mm、电流210A、扫描速度300mm/min;45钢经最佳激光淬火工艺,搭接率为44%的多道扫描激光淬火处理后,由表及里依次为完全相变硬化层、热影响区和基体,其中完全相变硬化层的组织为针状马氏体和残余奥氏体,深度为0.48 mm,硬度为842HV,比45钢整体淬火提高18%,热影响区的组织由完全马氏体逐渐转变为珠光体和铁素体组织,厚度为0.1~0.2mm,硬度从823HV到438HV呈梯度分布;相邻道与道之间的表面硬度从842HV到450HV呈梯度分布,热影响区宽度为0.3mm。2.点状、条纹状、网格状激光仿生强化单元体的磨损率分别为1.70×10-5mm3/(m·N)、 1.33×10-5 mm3/(m·N)、9.34×10-6 mm3/(m·N),基体的磨损率为2.38×10-5 mm3/(m·N),搭接试样的磨损率为1.54×10-5mm3/(m·N)。激光仿生强化试样和搭接试样的耐磨性均优于基体试样。从搭接试样和激光仿生强化试样的对比可见,搭接试样的耐磨性优于点状激光仿生强化试样,低于条纹状和网格状激光仿生强化试样。对比激光仿生强化试样的耐磨性可知,网格状激光仿生强化试样的磨损率最小,耐磨性最佳,条纹状激光仿生强化试样次之。3.激光仿生强化试样的抗拉强度和屈服强度均优于基体试样。在本文所研究的单元体形状中,条纹状试样的抗拉强度和屈服强度最高,较基体试样分别提高了10.8%和24.1%:网格状仿生强化试样次之,其抗拉强度和屈服强度分别提高了3.3%和16.7%;点状仿生强化试样的抗拉强度和屈服强度提高较低,分别为2.3%和12.2%。激光仿生强化处理的强化作用主要来源于单元体显微组织的变化和拉伸过程中拉应力由基体向单元体的传递。由于基体和单元体间的应力传递,故在相同载荷下,仿生强化试样基体中承受的拉应力要低于未处理试样,只有进一步增加载荷才能使其达到对应的临界应力,因此,激光仿生强化试样获得了更高的强度。
[Abstract]:Wear and fracture are the main causes of failure of metal parts, and these failure forms often occur on the surface of materials. Therefore, it is of great theoretical significance and practical value to improve the surface properties of metal parts and prolong their service life. In this paper, 45 steel, which is widely used in industry, is used as the experimental material. Firstly, the effects of defocusing, current and scanning speed on the hardness of quenching layer are studied by orthogonal test method, and the laser quenching process is optimized. Then on the basis of biomimetic research, the surface of the body with good wear resistance or resistance to breakage, such as leaves, hillbilly scabbard wings, dragonfly wings, shells, lizard horny scales, was used as the design prototype. A laser bionic strengthening unit was designed and fabricated. The wear and tensile properties of various laser bionic strengthening units were studied. The results show that: 1. The main factors affecting the hardness of the quenching layer are defocus, followed by electric current, and the optimum parameters of laser quenching are 22.5 mm, 210A, 300mm / min ~ (45) scanning speed and 44% lap ratio after laser quenching. The whole transformation hardening layer, the heat affected zone and the matrix are in order from the outside to the inside. The microstructure of the complete transformation hardening layer is acicular martensite and residual austenite. The hardness of 0.48 mm, is 842 HVV, which is 18% higher than that of 45 steel. The microstructure of the heat affected zone is gradually changed from complete martensite to pearlite and ferrite with a thickness of 0.1 ~ 0.2mm, and the hardness is distributed gradient from 823HV to 438HV. The surface hardness between adjacent channels is gradient distribution from 842HV to 450HV, and the width of heat affected zone is 0.3 mm. 2. The wear rate of point, stripe and grid laser biomimetic strengthening unit is 1.70 脳 10-5mm3/ (m N), 1.33 脳 10-5 mm3/ (m N), 9.34 脳 10-6 mm3/ (m N), matrix respectively. The wear rate of 2.38 脳 10-5 mm3/ (m N), lapping specimen is 1.54 脳 10-5mm3/ (m N). The wear resistance of the laser bionic strengthened specimen and the lapped specimen is better than that of the matrix sample. It can be seen from the comparison between the lapped specimen and the laser bionic strengthening specimen that the wear resistance of the lapped specimen is better than that of the point laser bionic strengthening specimen and is lower than that of the striped and grid laser bionic strengthening specimen. Compared with the wear resistance of the laser bionic strengthening specimen, the wear rate of the grid laser bionic strengthening specimen is the least, the wear resistance is the best, and the striped laser bionic strengthening specimen is the second. The tensile strength and yield strength of the laser bionic strengthening specimen are better than that of the matrix specimen. The tensile strength and yield strength of the striped specimen are the highest, which are 10.8% and 24.1% higher than that of the matrix sample, respectively. The tensile strength and yield strength were increased by 3.3% and 16.7%, respectively, and the tensile strength and yield strength of point bionic strengthening specimens were increased by 2.3% and 12.2%, respectively. The strengthening effect of laser bionic strengthening mainly comes from the change of microstructure and the transfer of tensile stress from the matrix to the unit during the tensile process. Because of the stress transfer between the matrix and the element body, the tensile stress in the matrix of the biomimetic strengthened specimen is lower than that in the untreated specimen under the same load, and the corresponding critical stress can be reached only by further increasing the load. The laser bionic strengthening specimen obtained higher strength.
【学位授予单位】:华东理工大学
【学位级别】:硕士
【学位授予年份】:2015
【分类号】:TG156.99

【参考文献】

相关期刊论文 前10条

1 张立文,裴继斌,陈,

本文编号:2283217


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