WC-Co硬质合金的小能多冲与静疲劳性能研究

发布时间：2018-05-22 11:46

本文选题：硬质合金 + 小能多冲　；参考：《湖南大学》2016年硕士论文

【摘要】：硬质合金以其优良的综合性能被广泛用于工业上,被誉为工业上的牙齿。硬质合金工具常处于小能量多次冲击碰撞的工况,所以研究硬质合金工具在小能量下服役的性能意义重大。本文以株洲硬质合金集团有限公司提供的六种WC-Co硬质合金为研究对象,对硬质合金进行两种实验方案的小能多冲实验以及硬质合金材料研究较少的静疲劳实验。另外分析了断口的宏观与微观断裂行为并探讨了粉末冶金缺陷对硬质合金性能的影响。主要研究结论如下：(1)实验合金力学性能测试结果表明：相同WC晶粒尺寸的硬质合金,随着Co含量的增多,其冲击韧性、抗弯强度与断裂韧性得到提高,硬度下降。相同Co含量的硬质合金,随着WC晶粒尺寸的增大,其硬度、冲击韧性、抗弯强度反而减小,断裂韧性得到提高。(2)两种小能多冲实验方案结果表明：实验合金在相同能量下冲击,Co含量越高,硬质合金小能多冲寿命越长,WC晶粒尺寸越大,小能多冲寿命越短：实验合金在相同的λ值(冲击能量与一次冲断能量的比值)对应能量下冲击,Co含量越高,小能多冲寿命越短,WC晶粒尺寸越大,小能多冲寿命短。Co含量最高的218#合金具有较高的疲劳敏感性,抗疲劳裂纹扩展能力较弱：Co含量最低的211#合金具有较低的疲劳敏感性,抗疲劳裂纹扩展能力较强。在工程技术上,这也表明高钴合金在服役条件下需要选择更高的安全系数。(3)通过对三种不同钴含量(11wt%,15wt%,18wt%)的硬质合金进行缺口样和光滑样的静疲劳性能研究对比,得出：合金在相同应力下静压,Co含量越高,静疲劳寿命越长,在相同θ值(施压在样品上的静态应力与该样品的抗弯强度之比)下静压,Co含量越高,静疲劳寿命越短,Co含量较低的211#合金有较低的疲劳敏感性,抗疲劳裂纹扩展能力较强。三种带缺口试样静疲劳寿命明显低于光滑试样,且在θ值为0.8时,钴含量为18wt%,15wt%,11wt%的三种合金光滑样与缺口样的静疲劳寿命比值分别约为1：2：7与1：1：2,这说明了缺口预制试样掩盖了硬质合金的缺陷。(4)硬质合金在小能量下服役(小能多冲与静疲劳试验)导致其断裂是由于内部孔洞(或粗大WC之类的缺陷)与实验过程中产生的缺陷在累积受力情况下慢慢长大,孔洞相互连接形成微裂纹,微裂纹慢慢长大达到临界裂纹长度时导致材料断裂。
[Abstract]:Cemented carbides are widely used in industry because of their excellent comprehensive properties. Cemented carbide tools are often in the condition of low energy impact and collision, so it is of great significance to study the performance of cemented carbide tools under low energy. In this paper, six kinds of WC-Co cemented carbides provided by Zhuzhou cemented Carbide Group Co., Ltd are taken as the research object. The small energy multi-impact experiments of two experimental schemes and the static fatigue tests of cemented carbide materials are carried out. In addition, the macroscopic and microscopic fracture behavior of fracture surface was analyzed and the influence of powder metallurgy defects on the properties of cemented carbide was discussed. The main conclusions are as follows: (1) the mechanical properties of the alloy show that the impact toughness, flexural strength and fracture toughness of the cemented carbide with the same WC grain size increase with the increase of Co content, and the hardness decreases. The hardness, impact toughness and bending strength of cemented carbides with the same Co content decrease with the increase of WC grain size. The experimental results of two kinds of small energy multiple impact test schemes show that the higher the impact Co content at the same energy, the longer the small energy multi-impact life of cemented carbides and the larger the WC grain size. The shorter the small energy multi-impact life is, the higher the impact Co content is at the same 位 value (the ratio of impact energy to primary thrust energy), and the smaller the small energy multi-impact life is, the larger the WC grain size is. The 218# alloy with the highest content of low energy multi-impact life has higher fatigue sensitivity, and the 211# alloy with the weakest crack growth resistance has lower fatigue sensitivity and stronger anti-fatigue crack propagation ability than the 211# alloy with the lowest fraction of small energy and multi-impact life, and the fatigue crack growth resistance of 218# alloy is higher than that of 211# alloy with the lowest fraction of small energy multi-impact life. In engineering technology, this also indicates that the high cobalt alloy needs to select a higher safety factor under service conditions.) by comparing the static fatigue properties of three kinds of cemented carbides with different cobalt contents of 11 wtt and 15 wtt and 18 wtts, the static fatigue properties of notched and smooth samples are studied and compared. It is concluded that the higher the content of Co under the same stress, the longer the static fatigue life of the alloy, and the higher the content of Co in the static pressure at the same 胃 value (the ratio of the static stress applied on the sample to the bending strength of the sample). The shorter the static fatigue life, the lower the fatigue sensitivity of 211# alloy, and the stronger the fatigue crack growth resistance. The static fatigue life of three notched specimens is obviously lower than that of smooth specimens, and when 胃 value is 0.8, The ratios of static fatigue life of three kinds of alloys with cobalt content of 18 wt% and 11wt% are about 1:2:7 and 1: 1: 2, respectively, indicating that the notched prefabricated specimens cover the defects of cemented carbides. Static fatigue test) the fracture is caused by internal holes (or defects such as large WC) and the defects produced in the course of experiments, which grow slowly under cumulative stress. The pores are connected to each other to form microcracks, and when the microcracks grow up to the critical crack length, they lead to the fracture of the material.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG135.5

【相似文献】