What is polycrystalline cubic boron nitride(CBN) cutting tool material?
What is polycrystalline cubic boron nitride(CBN) cutting tool material?Polycrystalline cubic boron nitride, CBN, is a cutting tool material with excellent hot hardness that can be used at very high cutting speeds. It also exhibits good toughness and thermal shock resistance.
Modern CBN grades are ceramic composites with a CBN content of 40–65%. The ceramic binder adds wear resistance to the CBN, which is otherwise prone to chemical wear. Another group of grades are the high-content CBN grades, with 85% to almost 100% CBN. These grades may have a metallic binder to improve their toughness.
CBN is brazed onto a cemented carbide carrier to form an insert.
CBN grades are largely used for finish turning hardened steels with a hardness over 45 HRC. Above 55 HRC, CBN is the only cutting tool that can replace traditionally used grinding methods. Softer steels, below 45 HRC, contain a higher amount of ferrite, which has a negative effect on the wear resistance of CBN.
CBN can also be used for the high-speed roughing of gray cast irons in both turning and milling operations.