What are PCBN Inserts? And what are the production methods?

PCBN (Polycrystalline Cubic Boron Nitride) is a new type of tool material whose hardness is second only to natural diamond by artificial methods. It is the most suitable tool material for high-speed cutting of iron-based metals.

There are two main methods for making PCBN blades: one is a one-time polymerization method, that is, hexagonal boron nitride (HBN) is directly polymerized into a high-density sintered body at one time;

The other is the secondary polymerization method. First, high-density cubic boron nitride (CBN) is synthesized, and then it is sintered into polycrystalline cubic boron nitride by high temperature and high pressure as raw material. The most common is the secondary polymerization method with the addition of a binder:

⑴ CBN sintering with metal binder

There are many types of metal binders, mainly Ni, Co, Ti, Ti-Al and so on. At the sintering temperature, the metal binder becomes a liquid phase, and the appearance of the liquid phase has a certain promotion effect on the sintering of CBN, and the sintering can be carried out at a slightly lower temperature and pressure. In addition, since CBN is insoluble in metal binders, the dissolution process that can promote shrinkage and crystal growth does not occur. During the sintering process, the cobalt in the cemented carbide penetrates into the CBN grain boundary in a liquid state, and the cemented carbide and the CBN sintered body are closely bonded together. The hardness of PCBN tool using metal binder is lower than that of pure CBN sintered tool, but the toughness is good. Brands such as AMB90 of Element six of the United Kingdom, BZN6000 of GE of the United States and MB710 of Mitsubishi of Japan are all sintered by metal binders.

(2) CBN sintering with ceramic binder added

Ceramic binders are mainly TiN, TiC, Al2O3 and so on. Since cracks are easy to occur during the sintering process, iron group elements (iron, cobalt, nickel) and Mo or Mo2C are often added to the ceramic binder to increase the strength between ceramic ions and act as a fluid pressure transfer medium, which is beneficial to To form a sintered body without internal deformation, molybdenum, etc. can also improve the wettability between the ceramic particles and the iron element. The content of the binder in the ceramic binder PCBN is generally higher, and the toughness is worse than that of the metal binder tool, but its high temperature resistance is better. Such products include DBA80 and DBC50 from Element six in the United Kingdom, BZN7000S and BZN8200 from GE in the United States, and NBX300 and NBX3200 from Sumitomo in Japan.

(3) Pure CBN sintering

In the CBN polycrystal, it can also be directly sintered without binder to form polycrystalline cubic boron nitride. During sintering, CBN undergoes a process of recrystallization and grain growth, and the grains of the sintered CBN polycrystals are no longer the original CBN single crystal grains. This kind of PCBN tool has good wear resistance and long life, but it is brittle and has harsh temperature conditions, so it is difficult to make high toughness and large-sized blades.