【作者】 毕泗庆；

【导师】 熊计；

【作者基本信息】 四川大学 ， 材料加工工程， 2007， 硕士

【摘要】 自德国人Karl Schroter于1923年用粉末冶金方法研制成WC-Co硬质合金以来，传统的硬质合金一直是以Co为主要粘结剂。但是Co是一种昂贵而稀缺的金属，世界储量极其有限。Fe、Ni与Co同属铁族金属，很多物理、化学性能相近，但Ni资源只是相对Co而言比较丰富，世界储量也很有限。Fe资源非常丰富，因此实现以Fe或部分Fe作硬质合金的粘结剂，具有重大的战略意义和经济意义。硬质合金按用途分为四个类别，分别以字母K，P，M和G表示。纯Fe代Co硬质合金应用很少，Fe部分代Co硬质合金一般都用于属于G类的矿山工具、石油钻探、地质勘探等，但在切削钢材等要求高硬度高耐磨性的场合研究很少。Fe基粘结剂硬质合金用于切削刀具时主要存在几个问题：①WC+Fe硬质合金的两相区太窄，控碳困难；②Fe基粘结剂硬质合金刀具易生锈③切削加工钢材时易与钢材粘结。本文通过添加Ni和TiC、优化控碳范围、优化烧结工艺和采用涂层技术来改善Fe代Co硬质合金的性能，并研究了这些因素对合金组织和性能的影响。首先通过配制5个不同碳含量的4种合金：WC+Fe、WC+TiC+Fe、WC+Ni+Fe和WC+TiC+Ni+Fe，来研究添加Ni和TiC对组织和性能的影响及最佳控碳范围。实验表明，添加Ni和TiC可以较明显地增大合金控碳范围，降低工艺的难度，而且添加Ni还可以明显提高合金的抗弯强度，添加TiC对硬度的提高也有一定的帮助。通过比较各种合金的组织和性能，得出WC+TiC+Ni+Fe系合金具有最佳的综合性能，其粉料的最佳控碳点在5.91％左右。然后针对WC+TiC+Ni+Fe合金，采用4种不同的烧结温度：1360℃、1400℃、1440℃和1480℃，研究烧结温度对合金组织和性能的影响。结果表明合金在1440℃达到“双高”，硬度为91.6HRA，强度为1720MPa，且组织正常，因此，烧结温度在1440℃左右适合此合金烧结。为了进一步考察WC+TiC+Ni+Fe合金的性能，制备了纯Fe和纯Co粘结剂合金：WC+TiC+Fe和WC+TiC+Co，以作对照。研究了它们涂层后的性能，包括切削性能。试验表明：Fe基粘结剂硬质合金的涂层结合强度良好，WC+TiC+Ni+Fe合金涂层前后的抗弯强度与传统的WC+TiC+Co合金相当，涂层技术有助于克服铁基粘结剂硬质合金刀具的锈蚀的问题。涂层前，WC+TiC+Ni+Fe和WC+TiC+Co合金刀片耐磨损和耐冲击性能相当。涂层后，在连续车削的初步试验中WC+TiC+Ni+Fe显示了较好的切削性能。涂层对于易与钢铁件粘结的Fe基粘结剂硬质合金刀具有较大的防护作用。更多还原

【Abstract】 Since Karl Schroter invented WC-Co cemented carbide by the powder metallurgy technology in 1923, cobalt is the main binder phase all along, but Co is expensive and rare and its’ reserves all over the world is very finite. Fe, Ni and Co all belongs to iron family metals in the periodic table of elements. Their physical and chemical properties are quite similar. The Ni resources are also not rich, but the Fe resources are very abundant. Therefore, Fe substitute for Co as the binder phase of cemented carbide has an important strategic and economic significance.According to the usage classification, the cemented carbide can be classified as four types: K, P, M and G. Fe replace entirely Co as binder phase is not often used, but Fe substitute for Co partly in G sort cemented carbide is generally used for mining tools, petroleum drilling, geological exploration etc. But if they are used to cut steel which need high hardness and abrasion performance, cemented carbides with Fe and Ni binder phase are confronted with the problems as follows:①The two phase zone of WC+Fe is too narrow to control the carbon content.②Tools with Fe binder phase is easy to be eroded seriously.③The tools and steels are easy adhere to each other at the cutting process. This paper researched on improving the performance of the cemented carbide tools with Fe binder phase prepared by adding Ni and TiC, optimizing carbon controlling range and sintering process and coating technology, and also studied the influences of these factors upon the microstructure and performance of the alloy.First of all, the influence of Ni and TiC on the structure and performance of cemented carbide and the best content of carbon were studied by preparing four kinds of cemented carbide with five grade carbon contents respectively. They were WC+Fe, WC+TiC+Fe, WC+Ni+Fe and WC+TiC+Ni+Fe cemented carbides. The results show that Ni and TiC can greatly enlarge carbon zone and reduce the difficulty of craft. The Ni can also obviously increase transverse rupture strength and TiC can increase hardness of the alloy. By comparing their structure and performance, we can conclude that WC+TiC+Ni+Fe cemented carbide has the best general performance among the four kinds of alloys. And the best content of carbon is around 5. 91%.Then we prepared the WC+TiC+Ni+Fe cemented carbide through sintering them at the temperature of 1360℃, 1400℃, 1440℃and 1480℃respectively to research the influence of the sintering temperature on the performance of the alloy. The results show that the alloy sintered at 1440℃has the best performance. The hardness and the transverse rupture strength are 91. 6HRA and 1720MPa respectively. Therefore the 1440℃is the best sintering temperature.Finally, in order to estimate the performance of the WC+TiC+Ni+Fe cemented carbide further, we prepared pure Fe binder cemented carbide and pure Co binder cemented carbide (WC+TiC+Fe, WC+TiC+Co). After coating the alloys, we studied their performance especially cutting performance. The results indicate that the cohesion strength between coating and substrate with Fe binder phase is better. The transverse rupture strength of WC+TiC+Ni+Fe cemented carbide with coating or not are as the same as WC+TiC+Co. And coating could prevent Fe binder phase cemented carbide from rust. And the abrasion resistance of WC+TiC+Fe, WC+TiC+Ni+Fe and WC+TiC+Co cemented carbide tools without coating are about the same. And the impact resistance increase as transverse rupture strength enhancing. Three kinds of coated tools’ machinability are good in the continuous cutting. And the coating can prevent the tools from adhering to the steels.更多还原