Nanotwinned Cubic Boron Nitride: Synthesis, Characterization and Wear Performance

Ultrahard materials with exceptional hardness, chemical inertness, thermal stability and excellent wear resistance are desirable for advanced tooling applications. The most important superhard materials, diamond and cubic boron nitride (cBN), are widely used for cutting, grinding, drilling and other modern processing applications.

Despite its lower hardness compared with diamond, cBN outcompetes diamond in many applications because of its superior thermal and chemical stability. It also has less affinity for iron than diamond, thereby making it more suitable for cutting and processing of iron-based alloys.

However, the synthesis of cBN remains limited due to pressure requirements. Moreover, it is costly and difficult to mass produce large-scale single crystals of cBN.

This material gap has motivated researchers to search for alternative, ultrahard materials with exceptional properties. Recently, a new type of superhard boron nitride, hexagonal boron nitride (h-BN), has been synthesized.

H-BN has a unique microstructure characterized by high-density and ubiquitously-occurring nanotwin substructures. Its unique nanotwinned microstructure provides high hardness, wear resistance, fracture toughness and thermal stability, which are essential for advanced cBN tool materials.