Tungsten Carbide - Wikipedia, The Free Encyclopedia
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Tungsten carbide
From Wikipedia, the free encyclopedia
Tungsten carbide (chemical formula: WC) is an inorganic chemical compound
(specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its
most basic form, tungsten carbide is a fine gray powder, but it can be pressed and
formed into shapes for use in industrial machinery, cutting tools, abrasives, other
tools and instruments, and jewelry.
Tungsten carbide is approximately two times stiffer than steel, with a Young's
modulus of approximately 550 GPa,[2] and is much denser than steel or titanium. It
is comparable with corundum (α-Al2O3) or sapphire/ruby in hardness and can only
be polished and finished with abrasives of superior hardness such as cubic boron
nitride and diamond, in the form of powder, wheels, and compounds.
Contents
Tungsten carbide
Tungsten carbide drilling/milling bits
Identifiers
CAS number 12070-12-1
PubChem
2724274
Jmol-3D
images
Image 1 (http://chemapps.stolaf.edu
/jmol/jmol.php?model=%5BC%5D%23%5BW%2B%5D)
1 Naming
SMILES
2 Synthesis
InChI
3 Chemical properties
4 Physical properties
5 Structure
6 Applications
6.1 Cutting tools for machining
6.2 Ammunition
6.3 Nuclear
6.4 Sports
Properties
Molecular
formula
WC
Molar mass
195.851 g/mol
Appearance Grey-black lustrous solid
Density
Melting point
15.63 g/cm3
2870 °C, 3143 K, 5198 °F
6.5 Surgical instruments
6.6 Jewelry
Boiling point
6000 °C, 6273 K, 10832 °F
6.7 Other
7 Toxicity
8 References
9 External links
Naming
Colloquially among workers in various industries (such as machining and
carpentry), tungsten carbide is often simply called carbide (without precise
distinction from other carbides). Among the lay public, the growing popularity of
tungsten carbide rings has led to some consumers calling the material just
tungsten, despite the inaccuracy of the usage.
Synthesis
WC can be prepared by reaction of tungsten metal and carbon at 1400–2000
°C.[3] Other methods include a patented lower temperature fluid bed process that
reacts either tungsten metal or blue WO3 with CO/CO2 mixture and H2 between
900 and 1200 °C.[4]
WC can also be produced by heating WO3 with graphite: directly at 900 °C or in
hydrogen at 670 °C following by carburization in Ar at 1000 °C.[5] Chemical vapor
deposition methods that have been investigated include:[3]
Solubility in
water
Insoluble
Structure
Crystal
structure
Hexagonal, hP2,
space group = P6m2, No. 187[1]
Hazards
EU
Not listed
classification
Related compounds
Other anions Tungsten boride
Tungsten nitride
Other cations Molybdenum carbide
Titanium carbide
Silicon carbide
(verify) (what is: / ?)
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C,
100 kPa)
Infobox references
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reacting tungsten hexachloride with hydrogen (as a reducing agent) and methane (as the source of carbon) at 670 °C
(1,238 °F)
WCl6 + H2 + CH4 → WC + 6 HCl
reacting tungsten hexafluoride with hydrogen (as reducing agent) and methanol (as source of carbon) at 350 °C (662 °F)
WF6 + 2 H2 + CH3OH → WC + 6 HF + H2O
Chemical properties
There are two well characterized compounds of tungsten and carbon, WC and tungsten semicarbide, W 2C. Both compounds
may be present in coatings and the proportions can depend on the coating method.[6]
At high temperatures WC decomposes to tungsten and carbon and this can occur during high-temperature thermal spray, e.g., in
high velocity oxygen fuel (HVOF) and high energy plasma (HEP) methods.[7]
Oxidation of WC starts at 500–600 °C.[3] It is resistant to acids and is only attacked by hydrofluoric acid/nitric acid (HF/HNO3)
mixtures above room temperature.[3] It reacts with fluorine gas at room temperature and chlorine above 400 °C (752 °F) and is
unreactive to dry H2 up to its melting point.[3] WC dissolves readily in diluted hydrogen peroxide.[8]
Physical properties
Tungsten carbide has a high melting point at 2,870 °C (5,200 °F), a boiling point of 6,000 °C (10,830 °F) when under a pressure
equivalent to 760mm of Hg,[9] a thermal conductivity of 84.02 W·m−1·K−1,[10] and a coefficient of thermal expansion of
5.8 µm·m−1·K−1.[11]
Tungsten carbide is extremely hard, ranking ~9 on Mohs scale, and with a Vickers number of 1700–2400.[12] It has a Young's
modulus of approximately 550 GPa,[2] a bulk modulus of 439 GPa,[13] and a shear modulus of 270 GPa.[11] It has a ultimate
tensile strength of 344.8 MPa.[14]
The speed of a longitudinal wave (the speed of sound) through a thin rod of tungsten carbide is 6220 m/s.[15]
With a low electrical resistivity of (~2×10−7 Ohm·m), tungsten carbide's resistivity is comparable with that of some metals (e.g.
vanadium 2×10−7 Ohm·m).[3][16]
WC is readily wetted by both molten nickel and cobalt.[17] Investigation of the phase diagram of the W-C-Co system shows that
WC and Co form a pseudo binary eutectic. The phase diagram also shows that there are so-called η-carbides with composition
(W,Co)6C that can be formed and the fact that these phases are brittle is the reason why control of the carbon content in WC-Co
hard metals is important.[17]
Structure
There are two forms of WC, a hexagonal form, α-WC (hP2, space group P6m2, No.
187),[1][18] and a cubic high-temperature form, β-WC, which has the rock salt
structure.[19] The hexagonal form can be visualized as made up of hexagonally close
packed layers of metal atoms with layers lying directly over one another, with carbon
atoms filling half the interstices giving both tungsten and carbon a regular trigonal
prismatic, 6 coordination.[18] From the unit cell dimensions [20] the following bond
lengths can be determined; the distance between the tungsten atoms in a
hexagonally packed layer is 291 pm, the shortest distance between tungsten atoms
in adjoining layers is 284 pm, and the tungsten carbon bond length is 220 pm. The
tungsten-carbon bond length is therefore comparable to the single bond in W(CH3)6
(218 pm) in which there is strongly distorted trigonal prismatic coordination of
tungsten.[21]
α-WC structure, carbon atoms are gray.[1]
Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for 184W 12C.[22]
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Applications
Cutting tools for machining
See also: Cemented carbide
Sintered tungsten carbide cutting tools are very abrasion resistant and can also withstand higher temperatures than standard high
speed steel tools. Carbide cutting surfaces are often used for machining through materials such as carbon steel or stainless
steel, as well as in situations where other tools would wear away, such as high-quantity production runs. Because carbide tools
maintain a sharp cutting edge better than other tools, they generally produce a better finish on parts, and their temperature
resistance allows faster machining. The material is usually called cemented carbide, hardmetal or tungsten-carbide cobalt: it is a
metal matrix composite where tungsten carbide particles are the aggregate and metallic cobalt serves as the matrix.
Manufacturers use tungsten carbide as the main material in some high-speed drill bits, as it can resist high temperatures and is
extremely hard.[23][24]
Ammunition
Tungsten carbide is often used in armor-piercing ammunition, especially where depleted uranium is not available or is politically
unacceptable. W 2C projectiles were first used by German Luftwaffe tank-hunter squadrons in World War II. Owing to the limited
German reserves of tungsten, W 2C material was reserved for making machine tools and small numbers of projectiles. It is an
effective penetrator due to its combination of great hardness and very high density.[25][26]
Tungsten carbide ammunition can be of the sabot type (a large arrow surrounded by a discarding push cylinder) or a subcaliber
ammunition, where copper or other relatively soft material is used to encase the hard penetrating core, the two parts being
separated only on impact. The latter is more common in small-caliber arms, while sabots are usually reserved for artillery
use.[27][28]
Nuclear
Tungsten carbide is also an effective neutron reflector and as such was used during early investigations into nuclear chain
reactions, particularly for weapons. A criticality accident occurred at Los Alamos National Laboratory on 21 August 1945 when
Harry K. Daghlian, Jr. accidentally dropped a tungsten carbide brick onto a plutonium sphere, causing the subcritical mass to go
supercritical with the reflected neutrons.
Sports
Hard carbides, especially tungsten carbide, are used by athletes, generally on poles
that strike hard surfaces. Trekking poles, used by many hikers for balance and to
reduce pressure on leg joints, generally use carbide tips in order to gain traction
when placed on hard surfaces (like rock); carbide tips last much longer than other
types of tip.[29]
While ski pole tips are generally not made of carbide, since they do not need to be
especially hard even to break through layers of ice, rollerski tips usually are. Roller
skiing emulates cross country skiing and is used by many skiers to train during warm
weather months.
A Nokian bicycle tire with tungsten carbide
Sharpened carbide tipped spikes (known as studs) can be inserted into the drive
spikes. The spikes are surrounded by
tracks of snowmobiles. These studs enhance traction on icy surfaces. Longer
aluminum.
v-shaped segments fit into grooved rods called wear rods under each snowmobile
ski. The relatively sharp carbide edges enhance steering on harder icy surfaces. The
carbide tips and segments reduce wear encountered when the snowmobile must cross roads and other abrasive surfaces.[30]
Some tire manufacturers offer bicycle tires with tungsten carbide studs for better traction on ice. These are generally preferred to
steel studs because of their superior resistance to wear.[31]
Tungsten carbide may be used in farriery, the shoeing of horses, to improve traction on slippery surfaces such as roads or ice.
Carbide-tipped hoof nails may be used to attach the shoes,[32] or alternatively borium, tungsten carbide in a matrix of softer metal,
may be welded to small areas of the underside of the shoe before fitting.[33]
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Surgical instruments
It is also used for making surgical instruments meant for open surgery (scissors, forceps, hemostats, blade-handles, etc.) and
laparoscopic surgery (graspers, scissors/cutter, needle holder, cautery, etc.). They are much costlier than their stainless-steel
counterparts and require delicate handling, but give better performance.[34]
Jewelry
Tungsten carbide, typically in the form of a cemented carbide (carbide particles held together by a metal), has become a popular
material in the bridal jewelry industry due to its extreme hardness and high resistance to scratching. Even with high-impact
resistance, this extreme hardness also means that it can occasionally be shattered under certain circumstances.[35] Tungsten
carbide is roughly 10 times harder than 18k gold. In addition to its design and high polish, part of its attraction to consumers is its
technical nature.[36]
Other
Tungsten carbide is widely used to make the rotating ball in the tips of ballpoint pens and other roller ballpoint pens that disperse
ink during writing.[37]
Tungsten carbide is a common material used in the manufacture of gauge blocks, used as a system for producing precision
lengths in dimensional metrology.[citation needed]
English guitarist Martin Simpson is known to use a custom made tungsten carbide guitar slide.[38] The hardness, weight, and
density of the slide give it superior sustain and volume compared to standard glass, steel, ceramic, or brass slides.
WC has been investigated for its potential use as a catalyst and it has been found to resemble platinum in its catalysis of the
production of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the
presence of water, and the isomerisation of 2,2-dimethylpropane to 2-methylbutane.[39] It has been proposed as a replacement
for the iridium catalyst in hydrazine powered satellite thrusters.[40]
Toxicity
The primary health risks associated with carbide relate to inhalation of dust, leading to fibrosis.[41] Cobalt–Tungsten Carbide is
also reasonably anticipated to be a human carcinogen by the National Toxicology Program.[42]
References
1. ^ a b c Krawitz, Aaron D.; Reichel, Daniel G.; Hitterman, Richard
6. ^ Jacobs, L.; M. M. Hyland; M. De Bonte (1998). "Comparative
(1989). "Thermal Expansion of Tungsten Carbide at Low
study of WC-cermet coatings sprayed via the HVOF and the
Temperature". Journal of the American Ceramic Society 72 (3):
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/10.1111%2Fj.1151-2916.1989.tb06169.x).
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(http://www.google.com/patents/US6447742) (2002)
Hydrogen Peroxide Characterized by 183W Nuclear Magnetic
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Resonance and Raman Spectroscopy". Chemistry of Materials
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16. ^ Kittel, Charles (1995). Introduction to Solid State Physics (7
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17. ^ a b Ettmayer, Peter; Walter Lengauer (1994). Carbides:
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(http://books.google.com/books?id=c0MUESWJo2oC&
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Publishing Company. pp. 13–. ISBN 978-0-913875-02-5.
31. ^ Hamp, Ron; Gorr, Eric and Cameron, Kevin (2011).
—Carbon". Journal of the American Ceramic Society 48 (5):
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(http://books.google.com/books?id=24kHuJV2LcAC&pg=PA69).
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20. ^ Rudy, E.; F. Benesovsky (1962). "Untersuchungen im System
32. ^ "Road nail" (http://www.mustadhoofnails.com/subcat
Tantal-Wolfram-Kohlenstoff". Monatshefte für chemie 93 (3):
/40/product/1369/page/0/road_nail/). Mustad Hoof Nails.
1176–1195. doi:10.1007/BF01189609 (http://dx.doi.org
Retrieved July 2011.
/10.1007%2FBF01189609).
21. ^ Kleinhenz, Sven; Valérie Pfennig; Konrad Seppelt (1998).
"Preparation and Structures of [W(CH3)6], [Re(CH3)6],
[Nb(CH3)6]−, and [Ta(CH3)6]−". Chemistry—A European
33. ^ Breningstall, F. Thomas. "Winter shoes"
(http://www.wiwfarm.com/wntrs.htm). Windt im Wald Farm.
Retrieved July 2011.
34. ^ Reichert, Marimargaret and Young, Jack H. (1997).
Journal 4 (9): 1687–91.
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(http://books.google.com/books?id=HDzcboqJR9kC&pg=PA30).
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Jones & Bartlett Learning. pp. 30–. ISBN 978-0-8342-0838-4.
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/the-new-luxury/breaking-tungsten-carbide/).
cherylkremkow.com (2009-10-29)
36. ^ Tungsten Carbide Manufacturing
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(http://books.google.com/books?id=3sS5a4jqzS8C&pg=PA30).
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38. ^ "Wolfram Martin Simpson Signature Slide"
http://en.wikipedia.org/wiki/Tungsten_carbide
communication". Catalysis Letters 45: 1–2.
(http://www.wolframslides.com/mssig.php). Wolfram Slides.
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/10.1023%2FA%3A1019059410876).
39. ^ Levy, R. B.; M. Boudart (1973). "Platinum-Like Behavior of
41. ^ Sprince, NL.; Chamberlin, RI.; Hales, CA.; Weber, AL.;
Tungsten Carbide in Surface Catalysis". Science 181 (4099):
Kazemi, H. (Oct 1984). "Respiratory disease in tungsten carbide
547–549. doi:10.1126/science.181.4099.547 (http://dx.doi.org
production workers". Chest 86 (4): 549–57.
/10.1126%2Fscience.181.4099.547). PMID 17777803
doi:10.1378/chest.86.4.549 (http://dx.doi.org
(//www.ncbi.nlm.nih.gov/pubmed/17777803).
/10.1378%2Fchest.86.4.549). PMID 6434250
40. ^ Rodrigues, J.A.J.; G.M. Cruz; G. Bugli; M. Boudart; G. DjégaMariadassou; (1997). "Nitride and carbide of molybdenum and
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External links
International Chemical Safety Card 1320 (http://www.inchem.org/documents/icsc/icsc/eics1320.htm)
NIOSH Pocket Guide to Chemical Hazards (http://www.cdc.gov/niosh/npg/npgd0647.html)
Retrieved from "http://en.wikipedia.org/w/index.php?title=Tungsten_carbide&oldid=577722659"
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Tungsten carbide
From Wikipedia, the free encyclopedia
Tungsten carbide (chemical formula: WC) is an inorganic chemical compound
(specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its
most basic form, tungsten carbide is a fine gray powder, but it can be pressed and
formed into shapes for use in industrial machinery, cutting tools, abrasives, other
tools and instruments, and jewelry.
Tungsten carbide is approximately two times stiffer than steel, with a Young's
modulus of approximately 550 GPa,[2] and is much denser than steel or titanium. It
is comparable with corundum (α-Al2O3) or sapphire/ruby in hardness and can only
be polished and finished with abrasives of superior hardness such as cubic boron
nitride and diamond, in the form of powder, wheels, and compounds.
Contents
Tungsten carbide
Tungsten carbide drilling/milling bits
Identifiers
CAS number 12070-12-1
PubChem
2724274
Jmol-3D
images
Image 1 (http://chemapps.stolaf.edu
/jmol/jmol.php?model=%5BC%5D%23%5BW%2B%5D)
1 Naming
SMILES
2 Synthesis
InChI
3 Chemical properties
4 Physical properties
5 Structure
6 Applications
6.1 Cutting tools for machining
6.2 Ammunition
6.3 Nuclear
6.4 Sports
Properties
Molecular
formula
WC
Molar mass
195.851 g/mol
Appearance Grey-black lustrous solid
Density
Melting point
15.63 g/cm3
2870 °C, 3143 K, 5198 °F
6.5 Surgical instruments
6.6 Jewelry
Boiling point
6000 °C, 6273 K, 10832 °F
6.7 Other
7 Toxicity
8 References
9 External links
Naming
Colloquially among workers in various industries (such as machining and
carpentry), tungsten carbide is often simply called carbide (without precise
distinction from other carbides). Among the lay public, the growing popularity of
tungsten carbide rings has led to some consumers calling the material just
tungsten, despite the inaccuracy of the usage.
Synthesis
WC can be prepared by reaction of tungsten metal and carbon at 1400–2000
°C.[3] Other methods include a patented lower temperature fluid bed process that
reacts either tungsten metal or blue WO3 with CO/CO2 mixture and H2 between
900 and 1200 °C.[4]
WC can also be produced by heating WO3 with graphite: directly at 900 °C or in
hydrogen at 670 °C following by carburization in Ar at 1000 °C.[5] Chemical vapor
deposition methods that have been investigated include:[3]
Solubility in
water
Insoluble
Structure
Crystal
structure
Hexagonal, hP2,
space group = P6m2, No. 187[1]
Hazards
EU
Not listed
classification
Related compounds
Other anions Tungsten boride
Tungsten nitride
Other cations Molybdenum carbide
Titanium carbide
Silicon carbide
(verify) (what is: / ?)
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C,
100 kPa)
Infobox references
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reacting tungsten hexachloride with hydrogen (as a reducing agent) and methane (as the source of carbon) at 670 °C
(1,238 °F)
WCl6 + H2 + CH4 → WC + 6 HCl
reacting tungsten hexafluoride with hydrogen (as reducing agent) and methanol (as source of carbon) at 350 °C (662 °F)
WF6 + 2 H2 + CH3OH → WC + 6 HF + H2O
Chemical properties
There are two well characterized compounds of tungsten and carbon, WC and tungsten semicarbide, W 2C. Both compounds
may be present in coatings and the proportions can depend on the coating method.[6]
At high temperatures WC decomposes to tungsten and carbon and this can occur during high-temperature thermal spray, e.g., in
high velocity oxygen fuel (HVOF) and high energy plasma (HEP) methods.[7]
Oxidation of WC starts at 500–600 °C.[3] It is resistant to acids and is only attacked by hydrofluoric acid/nitric acid (HF/HNO3)
mixtures above room temperature.[3] It reacts with fluorine gas at room temperature and chlorine above 400 °C (752 °F) and is
unreactive to dry H2 up to its melting point.[3] WC dissolves readily in diluted hydrogen peroxide.[8]
Physical properties
Tungsten carbide has a high melting point at 2,870 °C (5,200 °F), a boiling point of 6,000 °C (10,830 °F) when under a pressure
equivalent to 760mm of Hg,[9] a thermal conductivity of 84.02 W·m−1·K−1,[10] and a coefficient of thermal expansion of
5.8 µm·m−1·K−1.[11]
Tungsten carbide is extremely hard, ranking ~9 on Mohs scale, and with a Vickers number of 1700–2400.[12] It has a Young's
modulus of approximately 550 GPa,[2] a bulk modulus of 439 GPa,[13] and a shear modulus of 270 GPa.[11] It has a ultimate
tensile strength of 344.8 MPa.[14]
The speed of a longitudinal wave (the speed of sound) through a thin rod of tungsten carbide is 6220 m/s.[15]
With a low electrical resistivity of (~2×10−7 Ohm·m), tungsten carbide's resistivity is comparable with that of some metals (e.g.
vanadium 2×10−7 Ohm·m).[3][16]
WC is readily wetted by both molten nickel and cobalt.[17] Investigation of the phase diagram of the W-C-Co system shows that
WC and Co form a pseudo binary eutectic. The phase diagram also shows that there are so-called η-carbides with composition
(W,Co)6C that can be formed and the fact that these phases are brittle is the reason why control of the carbon content in WC-Co
hard metals is important.[17]
Structure
There are two forms of WC, a hexagonal form, α-WC (hP2, space group P6m2, No.
187),[1][18] and a cubic high-temperature form, β-WC, which has the rock salt
structure.[19] The hexagonal form can be visualized as made up of hexagonally close
packed layers of metal atoms with layers lying directly over one another, with carbon
atoms filling half the interstices giving both tungsten and carbon a regular trigonal
prismatic, 6 coordination.[18] From the unit cell dimensions [20] the following bond
lengths can be determined; the distance between the tungsten atoms in a
hexagonally packed layer is 291 pm, the shortest distance between tungsten atoms
in adjoining layers is 284 pm, and the tungsten carbon bond length is 220 pm. The
tungsten-carbon bond length is therefore comparable to the single bond in W(CH3)6
(218 pm) in which there is strongly distorted trigonal prismatic coordination of
tungsten.[21]
α-WC structure, carbon atoms are gray.[1]
Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for 184W 12C.[22]
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Applications
Cutting tools for machining
See also: Cemented carbide
Sintered tungsten carbide cutting tools are very abrasion resistant and can also withstand higher temperatures than standard high
speed steel tools. Carbide cutting surfaces are often used for machining through materials such as carbon steel or stainless
steel, as well as in situations where other tools would wear away, such as high-quantity production runs. Because carbide tools
maintain a sharp cutting edge better than other tools, they generally produce a better finish on parts, and their temperature
resistance allows faster machining. The material is usually called cemented carbide, hardmetal or tungsten-carbide cobalt: it is a
metal matrix composite where tungsten carbide particles are the aggregate and metallic cobalt serves as the matrix.
Manufacturers use tungsten carbide as the main material in some high-speed drill bits, as it can resist high temperatures and is
extremely hard.[23][24]
Ammunition
Tungsten carbide is often used in armor-piercing ammunition, especially where depleted uranium is not available or is politically
unacceptable. W 2C projectiles were first used by German Luftwaffe tank-hunter squadrons in World War II. Owing to the limited
German reserves of tungsten, W 2C material was reserved for making machine tools and small numbers of projectiles. It is an
effective penetrator due to its combination of great hardness and very high density.[25][26]
Tungsten carbide ammunition can be of the sabot type (a large arrow surrounded by a discarding push cylinder) or a subcaliber
ammunition, where copper or other relatively soft material is used to encase the hard penetrating core, the two parts being
separated only on impact. The latter is more common in small-caliber arms, while sabots are usually reserved for artillery
use.[27][28]
Nuclear
Tungsten carbide is also an effective neutron reflector and as such was used during early investigations into nuclear chain
reactions, particularly for weapons. A criticality accident occurred at Los Alamos National Laboratory on 21 August 1945 when
Harry K. Daghlian, Jr. accidentally dropped a tungsten carbide brick onto a plutonium sphere, causing the subcritical mass to go
supercritical with the reflected neutrons.
Sports
Hard carbides, especially tungsten carbide, are used by athletes, generally on poles
that strike hard surfaces. Trekking poles, used by many hikers for balance and to
reduce pressure on leg joints, generally use carbide tips in order to gain traction
when placed on hard surfaces (like rock); carbide tips last much longer than other
types of tip.[29]
While ski pole tips are generally not made of carbide, since they do not need to be
especially hard even to break through layers of ice, rollerski tips usually are. Roller
skiing emulates cross country skiing and is used by many skiers to train during warm
weather months.
A Nokian bicycle tire with tungsten carbide
Sharpened carbide tipped spikes (known as studs) can be inserted into the drive
spikes. The spikes are surrounded by
tracks of snowmobiles. These studs enhance traction on icy surfaces. Longer
aluminum.
v-shaped segments fit into grooved rods called wear rods under each snowmobile
ski. The relatively sharp carbide edges enhance steering on harder icy surfaces. The
carbide tips and segments reduce wear encountered when the snowmobile must cross roads and other abrasive surfaces.[30]
Some tire manufacturers offer bicycle tires with tungsten carbide studs for better traction on ice. These are generally preferred to
steel studs because of their superior resistance to wear.[31]
Tungsten carbide may be used in farriery, the shoeing of horses, to improve traction on slippery surfaces such as roads or ice.
Carbide-tipped hoof nails may be used to attach the shoes,[32] or alternatively borium, tungsten carbide in a matrix of softer metal,
may be welded to small areas of the underside of the shoe before fitting.[33]
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Surgical instruments
It is also used for making surgical instruments meant for open surgery (scissors, forceps, hemostats, blade-handles, etc.) and
laparoscopic surgery (graspers, scissors/cutter, needle holder, cautery, etc.). They are much costlier than their stainless-steel
counterparts and require delicate handling, but give better performance.[34]
Jewelry
Tungsten carbide, typically in the form of a cemented carbide (carbide particles held together by a metal), has become a popular
material in the bridal jewelry industry due to its extreme hardness and high resistance to scratching. Even with high-impact
resistance, this extreme hardness also means that it can occasionally be shattered under certain circumstances.[35] Tungsten
carbide is roughly 10 times harder than 18k gold. In addition to its design and high polish, part of its attraction to consumers is its
technical nature.[36]
Other
Tungsten carbide is widely used to make the rotating ball in the tips of ballpoint pens and other roller ballpoint pens that disperse
ink during writing.[37]
Tungsten carbide is a common material used in the manufacture of gauge blocks, used as a system for producing precision
lengths in dimensional metrology.[citation needed]
English guitarist Martin Simpson is known to use a custom made tungsten carbide guitar slide.[38] The hardness, weight, and
density of the slide give it superior sustain and volume compared to standard glass, steel, ceramic, or brass slides.
WC has been investigated for its potential use as a catalyst and it has been found to resemble platinum in its catalysis of the
production of water from hydrogen and oxygen at room temperature, the reduction of tungsten trioxide by hydrogen in the
presence of water, and the isomerisation of 2,2-dimethylpropane to 2-methylbutane.[39] It has been proposed as a replacement
for the iridium catalyst in hydrazine powered satellite thrusters.[40]
Toxicity
The primary health risks associated with carbide relate to inhalation of dust, leading to fibrosis.[41] Cobalt–Tungsten Carbide is
also reasonably anticipated to be a human carcinogen by the National Toxicology Program.[42]
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External links
International Chemical Safety Card 1320 (http://www.inchem.org/documents/icsc/icsc/eics1320.htm)
NIOSH Pocket Guide to Chemical Hazards (http://www.cdc.gov/niosh/npg/npgd0647.html)
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