As a synthetic superhard material, cubic boron nitride single crystals have become a key material in modern precision machining and advanced manufacturing due to their diamond-like hardness and unique physicochemical properties. Its crystal structure consists of boron and nitrogen atoms forming a covalent bond network through sp³ hybridization. With a Mohs hardness of 9.7 and a Vickers hardness exceeding 7000 HV, it maintains structural stability at temperatures up to 1200°C while exhibiting chemical inertness toward iron-group metals. These properties grant it irreplaceable advantages across multiple industrial applications.
In precision grinding, fine-grained cubic boron nitride single crystals are combined with ceramic or resin binders to create high-performance grinding wheels. For example, when machining high-speed steel hob teeth, ceramic-bonded CBN wheels achieve over 30% higher grinding efficiency than traditional alumina wheels while extending wheel life by 2-3 times. In automotive camshaft machining, CBN grinding wheels achieve operating speeds exceeding 160 m/s, reducing single-piece processing time from 5 minutes to under 2 minutes and significantly boosting production line cycle times. Their self-sharpening design enables abrasive grains to shed automatically after wear, maintaining sustained sharpness. This makes them particularly suitable for precision forming of high-toughness materials like hardened steel and titanium alloys.
As the fundamental raw material for cutting tools, micron-sized CBN single crystals are sintered under high temperature and pressure to form polycrystalline cubic boron nitride (PCBN), effectively overcoming the anisotropic defects of single crystals. In the automotive manufacturing industry, PCBN tools can directly machine hardened gears exceeding HRC 60, achieving a surface roughness of Ra 0.4 μm, with tool life 50 times that of cemented carbide. In the mold industry, PCBN machines HRC55 cold-worked mold cavities, enabling turning-instead-of-grinding processes that boost efficiency by 40%. For hard-face turning of bearing rings, PCBN tools ensure IT5 dimensional accuracy, reducing subsequent grinding operations.
Applications in electronics highlight its material advantages. As a wide-bandgap semiconductor, CBN features a bandgap of 6.4 eV and thermal conductivity of 79.54 W/m·K, enabling the fabrication of high-temperature-resistant, radiation-tolerant vacuum ultraviolet photodetectors. Research institutions are developing CBN-based MSM detectors with potential applications in aerospace thermal protection system monitoring. Its amber-to-black crystalline appearance has also been adopted by luxury brands for watch inlays, achieving a cross-disciplinary fusion of technology and aesthetics.
