There are two main methods for manufacturing PCBN blades: one is a one-time polymerization, that is, directly using hexagonal boron nitride (HBN) to polymerize into a high-density sintered body. The other is a secondary polymerization method. This method first synthesizes high-density cubic boron nitride (CBN), and then uses high temperature and high pressure as a raw material to form polycrystalline cubic boron nitride. At present, secondary polymerization methods with added binders are more common:
1. Add metal binder CBN sintering
There are many kinds of metal binders, mainly Ni, Co, Ti, ti-al, etc. At the sintering temperature, the metal binder becomes the liquid phase. The appearance of the liquid phase has a certain promoting effect on CBN sintering, and the sintering can be carried out at a slightly lower temperature and pressure. In addition, since CBN is insoluble in the metal binder, dissolution and precipitation process that can promote shrinkage and crystal growth will not occur. During the sintering process, cobalt in the cemented carbide penetrates into the CBN grain boundary in a liquid state, and the cemented carbide is closely bonded to the CBN sintered body. The hardness of the PCBN tool with a metal binder is lower than that of pure CBN sintered tool, but its toughness is good. Brands such as Element six’s AMB90, GE’s BZN6000 and Mitsubishi’s MB710 are all made of the sintered metal binder.
2. The addition of ceramic binder CBN sintering
Ceramic binder mainly includes TiN, TiC, Al2O3, etc. Crack due to sintering process, so much in the vitrified bond of iron group elements (iron, cobalt, nickel) and Mo or Mo2C increase strength between ceramic ion, have the effect of the medium of fluid transmitting pressure, is conducive to form internal sintered body without deformation, such as molybdenum can also improve the wettability between ceramic particles and iron. Ceramic binder PCBN binder content is generally higher, toughness than metal binder tool is poor, but its high-temperature resistance performance is better. Such products include DBA80 and DBC50 of British Element six company, BZN7000S and BZN8200 of American GE company, and NBX300 and NBX3200 of Sumitomo Japan.
3. Pure CBN sintering
Polycrystalline cubic boron nitride can also be formed by a direct sintering method so that a binder is not used in the CBN polycrystal. Recrystallization and grain growth occur during CBN sintering. The grains of CBN polycrystalline after sintering are not the original CBN single-crystal particles. This kind of PCBN tool has good wear resistance and long service life, but it is difficult to make the blade with high toughness and large size due to its brittleness and harsh temperature conditions.
Demina tool grinding machine can grind the PCBN blades with high efficiency. It can grind the edge and the circular arc of PCBN blades.