切削淬硬钢用PCBN复合片的合成研究

Synthesis Research of Polycrystalline Cubic Boron Nitride Composite for Cutting Hardened Steels

本文以cBN为原料,以TiN和Al为黏结剂,在1450℃左右的高温和5.5GPa的高压下,在铰链式六面顶压机内合成了四种不同cBN体积百分含量(vol%)的PCBN复合片。对合成的四种PCBN复合片进行了显微结构、相结构、硬度、体电阻率及切削性能等性能检测。结果显示:四种PCBN复合片的显微结构有明显的网格结构,网线处为黏结剂以及反应生成的产物,网孔处为BN相;cBN与黏结剂TiN、Al在烧结过程中发生反应,反应后Al相消失,生成AlN和TiB_2新物相,而PCBN50和PCBN60还有Al_3Ti相生成;PCBN复合片的硬度、电阻率随cBN含量的增加而增加,当cBN含量低于70vol%时,PCBN复合片的电阻率变化趋势较慢;随着cBN含量下降,刀具的切削寿命延长;当cBN含量小于70vol%时,湿式切削时的刀具寿命高于干式切削时,当cBN含量高于70vol%时,刀具干切时比湿切时使用寿命更长。

The four PCBN composites with different eBN volume percentages （vol%） have been synthesized by hinged cubic press at about 1450℃ and 5.5GPa by using cBN as raw materials,TiN and Al as binders. The effects of cBN contents on the properties of the four PCBN composites, including the microstructures, phase structure, hardness bulk electrical resistivity and cutting performance are studied. The results show that, the four PCBN composites have obvious network micro-structures, the binders and reaction products are usually at the edges of the networks,while BN phases present at the holes of the networks. The reactions between cBN and TiN, Al occur in sintering and AI is disappeared while AlN,TiB2 are generated after reaction. In addition, the Al3 Ti phase is presented in PCBN50 and PCBN60. The hardness and the electrical resistivity of PCBN composite increase with the increase of the cBN contents but the increasing trend of resistivity becomes small when cBN content is below 70vol%. The life-span of cutting tool becomes longer with the decrease of cBN contents. The life-span of cutting tools in wet cutting is longer than that in dry cutting, when cBN content is lower than 70vol% but the life-span of cutting tools in dry cutting is longer than that in wet cutting if the cBN content is higher than 70vol%.