Crushing Law of c'BN Particles under Ultra-High Pressure and Its Influence on Characteristics of Sintered PcBN
Cubic boron nitride(cBN)and carbon/nitride ceramic micro-powder were used as initial particles,and the extrusion experiment at room temperature and ultra-high pressure and sintering experiment at high temperature and high pressure were designed,respectively.Characterization was carried out using a laser particle size analyzer,SEM,and XRD.The study results show that the particle crushing and densification process of over 86.47%are completed within one minute under extrusion at ultra-high pressure.The particle crushing mechanism is manifested as brittle fractures and the formation of intragranular cracks.After crushing,it is easy to aggregate and has poor fluidity.The crushing rate of cBN particles is positively correlated with their grain size.Both cBN and ceramic micro-powder undergo two densification processes at ultra-high pressure,as well as high temperature and high pressure.The active surface and fine particles formed by particle crushing contribute to sintering densification.However,"internal injuries"such as cracks caused by particle crushing have a negative impact on the performance of the sintered body.
ultra-high pressurecrushing under extrusioncBNagglomerationcompression ratio
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