(1) high hardness and wear resistance.
CBN single-crystal microhardness of HV8000 ~ HV9000 is the second known high hardness material. The hardness of PCBN tool materials with different bonding amounts is between HV4000 ~ 6000, while the hardness of carbide tool materials is only between HV1100 ~ 1800.
The hardness of Al2O3 ceramic tool material is HV2000. It can be seen that PCBN tool has higher wear resistance than cemented carbide and ceramic when used for processing high hardness materials, which can reduce the size deviation or size dispersion in the processing of large parts, and reduce the time for tool changing and adjusting, so as to give full play to its efficiency.
(2) high thermal stability and high-temperature hardness.
The heat resistance of CBN can generally reach 1400 ~ 1500 ℃, while the normal temperature hardness of Al2O3 / TiC composite ceramic is 800 ℃. When the cutting temperature increases, the processed material will soften. The hardness difference between the tool and the tool will increase, which is beneficial to the cutting process but has little effect on the tool life.
(3) it has good thermal conductivity.
The thermal conductivity of CBN is up to 1300W/ (m ·K), which is 3.5 times that of purple steel. The thermal conductivity of cemented carbide is only 35 ~ 75W/ (m·K). The thermal conductivity of CBN material is lower than that of the diamond, but much higher than that of cemented carbide. In addition, the thermal conductivity of the PCBN tool increases with the improvement of cutting temperature. So the heat at the tooltip can be transferred quickly, which is conducive to the improvement of workpiece processing accuracy.
(4) high young’s modulus.
The young’s modulus of PCBN is about 750GPa, higher than WC, TiC, Al2O3, and other materials.
(5) has a small thermal expansion.
The thermal expansion coefficient of PCBN is about (2.1 ~ 2.3) ×10-6/K, while the thermal expansion coefficient of cemented carbide is (5 ~ 7) ×10-6/K.
(6) it has a small density.
The density of PCBN is 3.48g/cm3, which is close to that of Al2O3 and Si3N4.
(7) it has low fracture toughness.
The fracture toughness of PCBN is about (3.5 ~ 5) Pa·m0.5, which is only half of that of ceramic tool materials. This is the only shortcoming of PCBN.
(8) excellent chemical stability.
CBN has a high antioxidant capacity, in the atmosphere, 1000℃ does not produce an oxidation phenomenon, PCBN in 1300 ~ 1500℃ is still no a solution. Not corroded in acid. It is inert to iron group materials and does not produce a biochemical reaction at 1200 ~ 1300℃.
