多晶立方氮化硼在高压熔渗法烧结过程中的晶界键合机理研究

Study on CBN-CBN bonding mechanism in high pressure infiltration sintering of PCBN

为了探究多晶立方氮化硼（PCBN）在高压熔渗法烧结过程中的晶界键合机理，分别采用高压熔渗法和混合法，在烧结压力5．0～5．5GPa，温度1300～1600℃，加热时间10～15min条件下，对立方氮化硼（CBN）的烧结行为进行对比研究，并对烧结后的样品进行X射线衍射（XRD）物相分析，扫描电镜（SEM）分析和硬度测试。实验结果显示：在压力为5．5GPa，温度为1500℃条件下，利用熔渗法烧结的PCBN样品中出现了大量的CBN—CBN晶粒间键合；在同等压力温度条件下，利用熔渗法烧结样品的维氏硬度可达到CBN单晶硬度（45～50GPa）的80％以上，明显高于利用混合法烧结的样品。通过上述PCBN高温高压烧结行为的对比研究，系统分析高压熔渗法烧结过程中的CBN晶界键合机理。高压熔渗法有利于高温高压下CBN晶粒的塑性形变和晶粒间孔隙闭合，在CBN晶粒相互挤压处形成局部高应力区，从而在Si熔媒渗入CBN层后促进CBN—CBN晶粒间的键合。

Study on CBN-CBN bonding mechanism in the high pressure infiltration sintering of polycrystalline cubic boron nitride （PCBN） was carried out in the CBN-Si system. In the present study PCBN were sintered under high pressure and high temperature （HPHT） through infiltration method and mixed assembly method, respectively. The raw materials were sintered under 5.0--5.5 GPa, 1300 --1600 ℃ and 10--15 rain by the assembly through XRD, SEM, and hardness test. For methods mentioned above. The sampl CBN-Si system, results showed that C es were analyzed BN did not react with Si under the conditions of 5.0-- 5.5 GPa and 1300-- 1600 ℃ using either infiltration method or mixed assembly method. The samples sintered at 5.5 GPa and 1500 ℃ contained a large number of CBN-CBN bonding fabricated through the infiltration sintering process. PCBN with a much higher Vickers hardness could be obtain compared to the mixed assembly through method. infiltration sintering method at the same P-T conditions as The high pressure infiltration method was advantageous to plastic deformation sintered samples and The pore closing among the CBN grains, which could improve the grain 1o grain conlact during compression would form local densification of area with high stress, so as to promote molten Si layer infiltration CBN layer and fabricate CBN-CBN bonding among the CBN grain houndary