| The development of superhard cutting tools is rapidly, because universal application of CNC processing technology, especially the Pc BN tools. Polycrystalline cubic boron nitride(Pc BN) materials are sintered with c BN, Al, Ti C, Co and Al-Co alloy mixed bond system under high temperature and high pressure. And the impact of Pc BN performance with different binder content are investigated. Scanning electron microscope(SEM), energy dispersive spectrometer(EDS) and X-ray diffraction(XRD) are used to characterize the phase, microstructure and composition of the samples. Hardness and impact toughness testing of samples are measured with micro-hardness tester and the self-made ball impact tester, and its relationship with microstructure is analysed. The influence of Al-Co alloy on the comprehensive performance of sinter is analysed. The best ratio scheme of Al, Co content is got.The experimental results showed that, Al and c BN are react to new phase of Al N, Al B12 and Al B2, Ti C and c BN are react to new phase of Ti N and Ti B2, Co and c BN are react to new phase of Co N and Co2 B under conditions of 1400~1650 ℃and 90 MPa. The product of alloying Al-Co were Al5Co2 and Al13Co4, after HTHP they had not completely disappeared, but in the form of additional Al20Co4 exists, improve the hardness and impact toughness of sintered body to a certain extent. The best combination of selective binding agent are 10 wt%Al and 10 wt%Co by hardness and impact toughness test analysised.According to the best proportion of the binder, the effect of adding carbon nanotubes on the comprehensive property of Pc BN was studied. In the sintering process, CNT did not react with c BN and binder, but due to its strong adsorption capacity, c BN and binder were adsorbed on its surface. Also can promote c BN and binder bonding, to make sintered body microstructure more compact. Due to the difficulty of blending, the agglomeration phenomenon in sintered body became more obvious with the increase of the content of CNT, overall performance of the sintered body is reduced. When the content of CNT over the content of each bond element, a large number of CNT concentration under the action of HTHP, graphitization happende. When the content of CNT reaches 2 wt%, the comprehensive performance of hardness and impact toughness of sintered body reached the highest. The enhancement of CNT weakens the effect of pressure and temperature on hardness, improve the overall performance of the sintered body. |
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