What is tungsten heavy alloy?
Tungsten heavy alloy illustrate the advantages of microencapsulated powders. A brief background of this alloy system follows.
Tungsten alloygenerally are refractory metal, which have two-phase composites consisting of W-Ni- Fe or W-Ni- Cu or even W-Ni-Cu-Fe, some tungsten alloy is added Co、Mo、Cr, etc. They have very high melting point and have a density twice that of steel and are more than 50% heavier than lead. Tungsten content in conventional heavy alloys varies from 90 to 98 weight percent and is the reason for their high density (between 16.5 and 18.75 g/cc). Nickel, iron and copper serve as a binder matrix, which holds the brittle tungsten grains together and which makes tungsten heavy alloy ductile and easy to machine. Nickel-iron is the most popular additive, in a ratio of 7Ni:3Fe or 8Ni:2Fe (weight ratio). The conventional processing route for tungsten heavy alloy includes mixing the desired amount of elemental powders, followed by cold pressing and liquid phase sintering to almost full density. The matrix alloy melts and takes some tungsten into solution during liquid phase processing, resulting in a microstructure through which large tungsten grains (20–60µm) are dispersed in the matrix alloy. The as-sintered material often is subjected to thermo mechanical processing by swaging and aging, which results in increased strength and hardness in the heavy alloys.
The majority of current uses for WHAs (tungsten heavy alloy) are best satisfied with the W-Ni-Fe system. Alloys such as 93W-4.9Ni-2.lFe and 95W-4Ni-lFe represent common compositions. The addition of cobalt to a W-Ni-Fe alloy is a common approach for slight enhancement of both strength and ductility. The presence of cobalt within the alloy provides solid-solution strengthening of the binder and slightly enhanced tungsten-matrix interfacial strength. Cobalt additions of 5 to 15% of the nominal binder weight fraction are most common.
Some photos of tungsten alloy products from Chinatungsten
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As to is special properties, tungsten alloy material is usually used for tungsten alloy radiation shielding,tungsten alloy crankshaft, tungsten alloy counterweight, fishing sinkers, etc..
Tungsten Alloy Products v.s.Tungsten Carbide Products
Tungsten material is also made into tungsten carbide product, which is a chemical compound that contains carbon and tungsten and is similar to titanium carbide. It was originally developed for use as a cutting tool, in machine tools applications, where it still finds wide use today. Cemented tungsten carbide is neither a metal nor is it a ceramic. It is a cerametal although this isn't a widely used term. In most cases, tungsten carbide is simply referred to as carbide. Tungsten carbide alloys are prepared by reacting carbon and tungsten at a temperature of between 1400-2000ºC. With its highest hardness as 86~93 HRA (68~81HRC), excellent hot working performance, superior wear resistance and high cutting speed, but it is easily brickle, so tungsten carbide is widely used as cutting blade, drill, bits, nozzles, etc.
Compared with tungsten carbide, tungsten alloy have special properties as good elongation, small capacity with high density, good corrosion resistance, wonderful shock resistance, high radiation adsorption capability, minimal extruded metal pick-up and high impact resistance and crack resistance, tungsten alloy usually widely used as tungsten alloy radiation shielding, tungsten alloy crankshaft, tungsten alloy counterweight, etc.
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