pcBN

PCBN stands for polycrystalline cubic boron nitride, a synthetic ultra-hard material used in cutting tools for machining ferrous metals. It is one of the hardest materials known, second only to diamond, and offers excellent hot hardness, high wear resistance, and good chemical stability at elevated temperatures. PCBN is produced by sintering boron nitride powders into dense polycrystalline compacts, typically with a ceramic or metallic binder, under high pressure and high temperature to form solid tool inserts.

The material’s performance derives from its cubic boron nitride grains, which retain hardness at high cutting temperatures and resist chemical interaction with iron-containing workpieces. PCBN tools are particularly effective for hard turning and milling of hardened steels and some cast irons, where traditional carbide tooling wears rapidly. However, PCBN is relatively brittle and can be sensitive to impact or interrupted cuts, making overly aggressive feeds or poor tool geometry a risk for chipping or fracture. Compared with diamond, PCBN is more chemically stable for ferrous materials, but it remains more expensive and requires careful handling and preparation.

Grades of PCBN vary in grain size and binder content, affecting hardness, toughness, and edge life. Fine-grain or binderless variants generally offer higher wear resistance and finer finishes, while higher binder content can improve fracture toughness for interrupted cutting. Typical applications include hard turning of hardened steel (often above 45–50 HRC), tool steels, and some cast irons, with selective use in certain nickel-based alloys under appropriate conditions. PCBN remains a key option when tool life and performance in ferrous materials justify its higher cost.