Superhard materials (Review). Part II. Preparation, properties and application of composites based on superhard materials

An overview of superhard composite materials (microhardness or Vickers hardness of which is more than 40 GPa), as well as promising high-hardness materials with hardness HV = 30÷40 GPa, is presented. Superhard materials, first of all, include the diamond-silicon carbide composite (the highest properties are observed in the «Ideal» material synthesized in accordance with the Turing reaction-diffusion process) are characterized by a hardness of 62‒68 GPa. Boron suboxide and composite materials based on it, characterized by a Vickers hardness of 35‒40 GPa. Boron carbide has a high hardness (H μ = 49 GPa), however, with the introduction of sintering additives (hot-pressed materials), the hardness decreases ― HV = 34÷36 GPa. Monocrystalline and polycrystalline AlMgB 14 are characterized by HV = 32÷35 GPa, while composite materials AlMgB 14 + 30 % TiB 2 have an increased hardness of HV = 40÷46 GPa. The hardness values of promising high-hardness materials are also shown: borides of alkaline earth metals, borides of transition metals, borides of lanthanides, carbides of refractory metals, cubic silicon nitride c-Si 3 N 4 and nano-composite material n-TiN– α Si 3 N 4 .