Effect of CNTs on properties of PcBN composites with mixed particle size

Abstract

To improve the performance of PcBN composites prepared under high temperature and high pressure, mixed cBN particle sizes ranging from 0 to 0.5 μm and 0.5 to 1.0 μm were used as the raw material, Al-Ti-Al2O3 was used as the binder and the carbon nanotubes with different contents were added. The PcBN composites were prepared by sintering under high temperature and high pressure conditions. The effect of carbon nanotube content on the structure and properties of PcBN composites was investigated. The results show that there is no chemical reaction between PcBN and carbon nanotubes after the addition of carbon nanotubes, and the carbon nanotubes exist in the form of reinforcement inside the composite. The composite material is relatively dense, and the relative density of PcBN increases first and then decreases with the addition of carbon nanotubes. When the mass fraction of carbon nanotubes added is 1.5%, the relative density of PcBN reaches its maximum value of 97.9%, while PcBN has the maximum microhardness and fracture toughness of 3 892 HV and 6.82 MPa·m1/2, respectively. When the mass fraction of carbon nanotubes added is 1.0%, PcBN has the maximum bending strength and wear ratio, which are 584 MPa and 6 873 MPa, respectively. The pull-out and bridging effects of carbon nanotubes improve the mechanical properties of PcBN composites.

Keywords

• polycrystalline cubic boron nitride (pcbn)
• mixed particle size
• carbon nanotubes (cnts)
• high temperature and high pressure (hthp)
• mechanical property