Nano Tungsten Carbide Has Some Difficulties in Industrialization
Compared with tungsten carbide material with common grains (micron scale), nano-crystalline tungsten carbide has remarkable improvements in density, hardness, fracture toughness and wear resistance, etc. This is due to the grain size reaches nano scale, the volume of the grain decreases, the specific surface area becomes larger, the arrangement of atoms on the interface relative out of order, it will immigrate easily under deformation external interference and the material shows excellent toughness and ductility. Especially in nano tungsten carbide cutting tools, nano-scale microstructure phase due to the size effect, the grain boundary area increases, anti-crack propagation resistance improved, which is beneficial for obtaining excellent mechanical properties and machinability.
However, since the difficulties in manufacturing process, higher cost and nano grains grow easily in the process of sintering, tungsten carbide less than 100nm can not reach the level of industrial production. So the researchers have found that add nano grains in tungsten carbide matrix with fine grains, it can effectively improve the hardness and toughness of the matrix materials. Now the enterprises use nano composite reinforced method to improve the properties of tungsten carbide material with fine grains. The principle of nano tungsten carbide composite strengthening mechanism is nano grain dispersed in the matrix has dispersed toughening effect. When added to a high elastic modulus of the matrix material in the second phase particles (nano particles), these particles in the matrix material by stretching action will prevent the transverse cross-section contraction, but to achieve the same substrate transverse shrinkage, the increase in the large longitudinal tensile stress, so that the material can consume more energy, toughening effect works. At the same time, high modulus particles crack can act as a "pinning" effect, so that the crack deflection, deviation, thereby dissipating power forward crack, so the toughening effect works. In addition, the dispersed nano grains in tungsten carbide matrix can inhibit the growth of carbide grains during the sintering process and greatly improve the mechanical properties of tungsten carbide materials.
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