VC/Cr3C2添加剂与烧结温度对超细WC-12Co硬质合金的影响

为了有效控制烧结过程中WC晶粒的长大,获得高强度高硬度的超细硬质合金,采用扫描电镜、拉伸机和洛氏硬度仪研究了不同质量分数及配比的VC/Cr3C2晶粒长大抑制剂和烧结温度对超细WC-12Co硬质合金的显微组织及力学性能的影响,并结合试验结果分析了超细硬质合金中VC/Cr3C2晶粒长大抑制剂的作用机理.结果表明,添加适量VC/Cr3C2晶粒长大抑制剂的超细硬质合金中WC晶粒尺寸分布集中,不存在明显的组织缺陷,合金具有细而均匀的微观组织及优异的力学性能.当晶粒长大抑制剂(质量分数)为0.2%VC/0.5%Cr3C2,1450℃烧结制备WC-12Co超细硬质合金的抗弯强度为3710MPa,硬度(HRA)为91.5.VC/Cr3C2晶粒长大抑制剂的作用机理为:VC主要与WC反应生成(W,V)C固溶体聚集在WC/Co界面,降低WC/Co界面能,Cr3C2主要固溶在粘结相中,导致WC在粘结相中的溶解度降低,二者的综合作用减缓了粘结相中WC溶解-析出过程,从而抑制烧结过程中WC晶粒的长大.

Effect of VC/Cr3C2 inhibitors and sintering temperature on ultrafine WC-12Co alloys

In order to inhibit the grain growth of WC during the sintering process and obtain ultrafine WC-12Co alloys with high strength and hardness,the influence of VC/Cr3C2 inhibitors and sintering temperature on the microstructure and mechanical properties of ultrafine WC-12Co was investigated using JSM-5600LV scanning electron microscope,LJ-3000 stretcher and Rockwell HR-150 sclerometer.The mechanism of grain growth inhibition was also analyzed.The results show that alloys with homogeneous microstructure and excellent properties are obtained when the optimal proportion of additions is added.Sintered at 1450 ℃,the transverse rupture strength and hardness reach 3710 MPa and 91.5 HRA for the ultrafine WC-12Co alloy with 0.2% VC/0.5% Cr3C2(wt%).The mechanism of VC/Cr3C2 inhibitors is that the reaction between WC and VC leads to the presence of small(V,W) C precipitates on WC/Co interfaces,which decreases the interfacial energy;on the other hand,Cr3C2 mainly dissolved in the binder phase reduces the solubility of WC in the binder phase.The driving force for WC grain growth from reprecipitation process is decreased and WC grain growth is retarded.