含纳米金刚石的立方氮化硼聚晶的制备

Preparation of Cubic Boron Nitride Polycrystalline Containing Nanodiamond

采用在cBN表面进行镀钛、并在PcBN结合剂中加入纳米金刚石的方法,对静压法合成的PcBN的组织结构进行研究。通过对镀钛后的cBN和合成的PcBN样品进行XRD、SEM、显微硬度、致密度分析和热稳定性分析,并与结合剂中不含纳米金刚石的PcBN样品进行对比,研究纳米金刚石的添加对合成PcBN的组织结构和性能的影响。实验结果表明,在有镀钛cBN、Al和Si存在的环境中,采用先升压至5.5 GPa,然后升温至1 400℃,保温保压500 s的合成工艺,在PcBN中未发现纳米金刚石发生石墨化;作为碳源,与Si、Ti、Al等共同作用,在PcBN组织中形成多种耐热、高硬、稳定的化合物。适当过量地加入使得PcBN组织中残留部分未反应的纳米金刚石,不仅提高了PcBN的致密性,而且提高了PcBN的硬度,更为重要的是消除和减轻了"架桥"现象。在合成PcBN的过程中,Ti和纳米金刚石的反应活性最强。结合真空微蒸发镀钛技术,cBN表面镀钛和加入纳米金刚石使PcBN中的各组分之间充分反应形成的多种化合物过渡层,使得PcBN中各相之间有良好的相容性,PcBN的热稳定性得到提高。

The polycrystalline cBN was prepared at 5.5 GPa and 1 400℃ for 500 s. The cBN was coated with titanium by vacuum slow vaporizing technology, and nanodiamond, aluminum and silicon were also used as additives to binding components. By SEM and XRD inspections,the structure and phases of PcBN were identified. The density, microhardness and heat endurance of PcBN were also tested. The effects of Ti-coating and nanodiamond in PcBN were studied. The results showed that nanodiamond could be used as carbon source to react with silicon, titanium and aluminum to form various compounds with super hardness,high heat resistance and high stability. These compounds improved the structure consistency and eliminated the extra residual stress between different substances. The residual nanodiamond in PcBN was still in diamond structure,and was not graphitized during the sintering. It not only increased the density and hardness of PcBN,but also reduced the ＂bridging effect＂. As there were so many kinds of compounds distributed in the binder,the compatibility was improved and the heat endurance of PeBN was increased.