WC–xVC复合粉的制备及高含量VC对WC–Co基硬质合金微观结构和力学性能的影响

Preparation of WC-xVC composite powders and the effect of high content VC on microstructure and mechanical properties of WC-Co based cemented carbides

采用两步碳热还原法合成了WC–xVC复合粉,并以此为原料通过真空烧结法制备了不同Co含量(6%和10%,质量分数)的WC–Co–VC硬质合金,研究了烧结温度(1420℃、1440℃和1460℃)对硬质合金致密化过程的影响,分析了Co和VC含量对WC晶粒尺寸以及硬质合金维氏硬度和断裂韧性的影响。结果表明,随着烧结温度的升高,合金的相对密度增大,当烧结温度为1460℃时,所有合金试样的相对密度均大于98.5%。此外,随着VC含量的增加,WC的平均晶粒尺寸减小,这导致样品的硬度提高,断裂韧性降低。当VC质量分数为6%时,WC–6Co硬质合金和WC–10Co硬质合金的硬度均达到最大值,分别为HV301941和HV301838。在烧结温度和VC含量一定的情况下,试样的断裂韧性随着Co含量的增加而增加,试样的硬度随着Co含量的增加而减小。

The WC–xVC composite powders were synthesized by two-step carbothermal reduction process,and the WC–Co–VC cemented carbides with different mass fraction of Co(6%and 10%)were prepared by vacuum sintering method using the WC–xVC composite powders as the raw materials.The effect of sintering temperature(1420℃,1440℃,and 1460℃)on the densification process of the cemented carbides was studied.Meanwhile,the effects of Co and VC content on the grain size,hardness,and fracture toughness of the WC samples were investigated.The experimental results show that the relative density of the alloys increases with the increase of sintering temperature.When the sintering temperature is 1460℃,the relative density of each sample is greater than 98.5%.With the increase of VC addition amount,the average grain size of WC decreases,which leads to the increase of hardness and the decrease of fracture toughness.When the VC mass fraction is 6%,the hardness of the WC–6Co cemented carbides and the WC–10Co cemented carbides reaches the maximum as HV301941 and HV301838,respectively.In addition,under the certain condition of sintering temperature and VC content,the fracture toughness of the samples increases with the increase of Co content,and the hardness of the samples decreases.