激光表面淬火对材料疲劳性能的影响研究

发布时间：2018-03-25 02:14

本文选题：激光淬火　切入点：Basquin模型　出处：《西南石油大学》2015年硕士论文

【摘要】：井下工具的疲劳给油田生产带来严重的经济损失,如何提高其疲劳性能是一项亟待解决的问题。激光表面淬火是近年来新兴的一项表面处理技术,无论是其理论研究发展或实际生产应用,都已经较为成熟。激光表面淬火使金属表面迅速加热至相变点以上,金属组织奥氏体化,而后随着材料的自身冷却,奥氏体迅速转变为马氏体。在这整个过程中,材料心部组织不变,因此得到了心部韧性好而表面硬度较高的组织。国内外生产已经将激光表面淬火用于航天、汽车、冶金、磨具、机械生产等各行业,一些石油工具也用激光淬火来优化其性能。激光淬火技术应用广泛,然而影响激光淬火质量的工艺参数有多个,若想要得到预期的强化效果,应对各种工艺参数的影响规律进行具体的研究。本文研究了激光淬火对某井下工具用钢的疲劳性能的影响规律。激光淬火处理的工艺参数主要包括激光功率P、扫描速度v和光斑大小D等。本文根据实际调研情况,具体研究了激光功率和扫描速度对材料疲劳性能的影响。文中采用CO2激光器对旋转弯曲疲劳试样进行激光淬火处理,而后在PQ-6旋转弯曲疲劳试验机上进行疲劳实验；按照数理统计方法对疲劳实验结果进行分析,对比不同激光淬火工艺参数处理的试样与原始试样S-N曲线的差异；利用扫描电子显微镜对疲劳试样的断口进行分析,对比不同工艺试样疲劳裂纹源区、扩展区和瞬断区的差异；利用金相显微镜和显微硬度分析仪确定淬硬层组织及其厚度。实验发现,激光淬火功率对材料的疲劳性能的影响较大,淬火功率过低,材料表面达不到强化效果,功率太高,淬火层厚度太厚,反倒使得疲劳极限降低,因此在实际操作中要选择使淬硬层厚度在1.5mm左右的功率；在同样功率下,不同扫描速度对激光淬火材料的疲劳性能影响较小,淬硬层厚度随着扫描速度的增加略有减小。
[Abstract]:Fatigue of downhole tools brings serious economic losses to oil field production. How to improve their fatigue performance is an urgent problem to be solved. Laser surface quenching is a new surface treatment technology in recent years. The laser surface quenching makes the metal surface rapidly heated above the transformation point, and the structure of the metal becomes austenitic, and then with the cooling of the material itself, The austenite was rapidly transformed into martensite. During the whole process, the core structure of the material remained unchanged, so the microstructure with good core toughness and high surface hardness was obtained. Laser surface quenching has been used in aerospace, automotive, metallurgical, domestic and foreign production. In various industries such as grinding tools and mechanical production, some petroleum tools also use laser quenching to optimize their performance. Laser quenching technology is widely used, but there are many technological parameters that affect the quality of laser quenching. The influence law of various technological parameters should be studied concretely. The effect of laser quenching on fatigue properties of a underground tool steel is studied in this paper. The technological parameters of laser quenching mainly include laser power, scanning speed v and spot size D etc. The influence of laser power and scanning speed on the fatigue properties of the material was studied. In this paper, CO2 laser was used to quench the rotating bending fatigue specimen, and then the fatigue test was carried out on the PQ-6 rotating bending fatigue tester. The fatigue test results were analyzed according to the mathematical statistics method, the differences of S-N curves between the samples treated with different laser quenching process parameters and the original samples were compared, and the fracture surface of the fatigue specimen was analyzed by scanning electron microscope (SEM). The microstructure and thickness of hardened layer were determined by metallographic microscope and microhardness analyzer. The influence of laser quenching power on the fatigue properties of the material is great, the quenching power is too low, the surface of the material can not be strengthened, the power is too high, the thickness of the quenched layer is too thick, and the fatigue limit is reduced. Therefore, in practice, we should choose the power to make the thickness of hardened layer about 1.5mm, and at the same power, the different scanning speed has little effect on the fatigue properties of laser quenched material, and the thickness of hardened layer decreases slightly with the increase of scanning speed.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG665

【参考文献】