After more than 30 years of development, PCBN tools have gradually matured since the development of cubic boron nitride (CBN) single crystal powder by GE in 1957 and PCBN tools in the 1970s. Currently, PCBN tools are mostly made of PCBN inserts welded to tool bars or indexable inserts, and in recent years, there are more and more types of integral PCBN inserts. This material has both the high hardness, high thermal stability and high chemical stability of PCBN and the advantages of good strength and weldability of cemented carbide, making PCBN tools not only capable of cutting workpieces of various hardnesses, but also easy to produce. the quality of PCBN inserts directly affects the cutting performance of the tools. 2.1 Sintering of PCBN inserts There are two main methods of making PCBN inserts: one is the primary polymerization method, which is directly polymerized with hexagonal boron nitride (HBN) into a high-density sintered body; the other is the secondary polymerization method, which first synthesizes high-density cubic boron nitride (CBN), and then uses it as the raw material to be sintered into polycrystalline cubic boron nitride by high temperature and pressure. At present, the more common is the secondary polymerization method with the addition of binder.
(1) CBN sintering with the addition of metal binder There are many types of metal binders, mainly Ni, Co, Ti, Ti-Al, etc. At the sintering temperature, the metal binder becomes the liquid phase, and the appearance of the liquid phase has a certain promotion effect on CBN sintering, which can be carried out at a slightly lower temperature and pressure. In addition, since CBN is insoluble in the metal binder, no dissolution precipitation process occurs that can promote shrinkage and crystal growth. During the sintering process the cobalt in the cemented carbide penetrates into the CBN grain boundaries in a liquid state, bonding the carbide to the CBN sintered body. The hardness of PCBN tools with metal binder is lower than that of pure CBN sintered tools, but the toughness is better. Grades such as AMB90 from Element six (UK), BZN6000 from GE (USA) and MB710 from Mitsubishi (Japan) are sintered with metal binder.
(2) CBN sintering with ceramic binder The ceramic binder mainly includes TiN, TiC, Al2O3, etc. Since the sintering process is prone to cracking, the addition of iron group elements (Fe, Co, Ni) and Mo or Mo2C in the ceramic binder increases the strength of the ceramic ions, plays the role of a fluid pressure transfer medium, and is conducive to the formation of internal deformation-free sintered bodies. Ceramic binder PCBN in the binder content is generally higher, poorer toughness than metal binder tool, but its resistance to high temperatures is better. These products are DBA80, DBC50 of British Element six, BZN7000S and BZN8200 of American GE, NBX300 and NBX3200 of Japanese Sumitomo, etc.
(3) Pure CBN sintering The CBN polycrystals can also be sintered directly without binder to make polycrystalline cubic boron nitride (CBN). This PCBN tool has good wear resistance and long life, but is brittle and temperature conditions are harsh, difficult to make high toughness and large size inserts. Translated with www.DeepL.com/Translator (free version)
(1) CBN sintering with the addition of metal binder There are many types of metal binders, mainly Ni, Co, Ti, Ti-Al, etc. At the sintering temperature, the metal binder becomes the liquid phase, and the appearance of the liquid phase has a certain promotion effect on CBN sintering, which can be carried out at a slightly lower temperature and pressure. In addition, since CBN is insoluble in the metal binder, no dissolution precipitation process occurs that can promote shrinkage and crystal growth. During the sintering process the cobalt in the cemented carbide penetrates into the CBN grain boundaries in a liquid state, bonding the carbide to the CBN sintered body. The hardness of PCBN tools with metal binder is lower than that of pure CBN sintered tools, but the toughness is better. Grades such as AMB90 from Element six (UK), BZN6000 from GE (USA) and MB710 from Mitsubishi (Japan) are sintered with metal binder.
(2) CBN sintering with ceramic binder The ceramic binder mainly includes TiN, TiC, Al2O3, etc. Since the sintering process is prone to cracking, the addition of iron group elements (Fe, Co, Ni) and Mo or Mo2C in the ceramic binder increases the strength of the ceramic ions, plays the role of a fluid pressure transfer medium, and is conducive to the formation of internal deformation-free sintered bodies. Ceramic binder PCBN in the binder content is generally higher, poorer toughness than metal binder tool, but its resistance to high temperatures is better. These products are DBA80, DBC50 of British Element six, BZN7000S and BZN8200 of American GE, NBX300 and NBX3200 of Japanese Sumitomo, etc.
(3) Pure CBN sintering The CBN polycrystals can also be sintered directly without binder to make polycrystalline cubic boron nitride (CBN). This PCBN tool has good wear resistance and long life, but is brittle and temperature conditions are harsh, difficult to make high toughness and large size inserts. Translated with www.DeepL.com/Translator (free version)