As a tool material, the quality of polycrystalline cubic boron nitride composite sheet directly affects the cutting power and service life of PCBN tools.
The following polycrystalline cubic boron nitride composite sheet, polycrystalline diamond composite sheet and oil drill bit manufacturers talk about the primary research and development process of polycrystalline cubic boron nitride composite sheet.
(1) Binder. Polycrystalline cubic boron nitride composite sheet is formed by sintering cubic boron nitride particles and a certain proportion of binder under high temperature and high pressure. Binder plays an important role in the process of forming PCBN. Adding an appropriate amount of binder can reduce the sintering temperature and pressure and improve the performance of the sintered body. When selecting a binder, the following points should generally be followed:
a. The linear expansion coefficient should be as close as possible to that of cubic boron nitride to reduce temperature stress;
b. The binder should have a strong chemical affinity with nitrogen or boron elements to improve the bonding strength;
c. It can firmly connect the cemented carbide substrate;
d. When PCBN processes different metal materials, the content of the binder has a great influence on the cutting effect. Therefore, when making PCBN with a high binder content, the binder should have higher hardness and toughness.
(2) Sintering process. The main parameters in the sintering process of polycrystalline cubic boron nitride composite sheets are pressure, temperature and sintering time. Sintering should be controlled in the thermal stability zone of cubic boron nitride. During the sintering process, the temperature is generally marked by the heating power.
Because the optimal power value of sintering is very close to the power value of the reverse conversion of cubic boron nitride to hexagonal boron nitride, the selectable sintering temperature range is very narrow, generally 1400C ~ 1600°C, the pressure range is about 5.0~7.0GPa,
and the holding time is about 2~30 minutes. In addition, the uneven temperature distribution in the high-pressure container also affects the quality and performance of PCBN.
