Tungsten carbide - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Tungsten_carbide
Tungsten carbide From Wikipedia, the free encyclopedia
Tungsten carbide (chemical formula: WC) is an inorganic chemical compound Tungsten carbide (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 [2] modulus of approximately 550 GPa, and is much denser than steel or titanium. It Tungsten carbide drilling/milling bits is comparable with corundum (α Al O ) or sapphire/ruby in hardness and can only 2 3 Identifiers be polished and finished with abrasives of superior hardness such as cubic boron nitride and diamond, in the form of powder, wheels, and compounds. CAS number 12070 12 1 PubChem 2724274 Jmol 3D Image 1 (http://chemapps.stolaf.edu Contents images /jmol/jmol.php?model=%5BC %5D%23%5BW%2B%5D) 1 Naming SMILES 2 Synthesis InChI 3 Chemical properties Properties 4 Physical properties Molecular WC 5 Structure formula 6 Applications Molar mass 195.851 g/mol 6.1 Cutting tools for machining Appearance Grey black lustrous solid 6.2 Ammunition Density 15.63 g/cm 3 6.3 Nuclear Melting point 6.4 Sports 2870 °C, 3143 K, 5198 °F 6.5 Surgical instruments Boiling point 6.6 Jewelry 6000 °C, 6273 K, 10832 °F 6.7 Other Solubility in Insoluble 7 Toxicity water 8 References Structure 9 External links Crystal Hexagonal, hP2, structure space group = P 6m2, No. 187 [1] Naming Hazards EU Not listed Colloquially among workers in various industries (such as machining and classification carpentry), tungsten carbide is often simply called carbide (without precise Related compounds distinction from other carbides). Among the lay public, the growing popularity of Other anions Tungsten boride tungsten carbide rings has led to some consumers calling the material just tungsten , despite the inaccuracy of the usage. Tungsten nitride Other cations Molybdenum carbide Synthesis Titanium carbide Silicon carbide WC can be prepared by reaction of tungsten metal and carbon at 1400–2000 (verify) (what is: / ?) °C. [3] Other methods include a patented lower temperature fluid bed process that Except where noted otherwise, data are given for reacts either tungsten metal or blue WO 3 with CO/CO 2 mixture and H 2 between materials in their standard state (at 25 °C, [4] 900 and 1200 °C. 100 kPa) Infobox references WC can also be produced by heating WO 3 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]
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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)
WCl 6 + H 2 + CH 4 → WC + 6 HCl
reacting tungsten hexafluoride with hydrogen (as reducing agent) and methanol (as source of carbon) at 350 °C (662 °F)
WF 6 + 2 H 2 + CH 3OH → WC + 6 HF + H 2O 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]
[3] Oxidation of WC starts at 500–600 °C. It is resistant to acids and is only attacked by hydrofluoric acid/nitric acid (HF/HNO 3) mixtures above room temperature. [3] It reacts with fluorine gas at room temperature and chlorine above 400 °C (752 °F) and is [3] [8] unreactive to dry H 2 up to its melting point. WC dissolves readily in diluted hydrogen peroxide. 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 m 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 P 6m2, 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(CH 3)6 α WC structure, carbon atoms are gray. [1] (218 pm) in which there is strongly distorted trigonal prismatic coordination of tungsten. [21]
Molecular WC has been investigated and this gas phase species has a bond length of 171 pm for 184 W12 C. [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.
Sharpened carbide tipped spikes (known as studs) can be inserted into the drive A Nokian bicycle tire with tungsten carbide tracks of snowmobiles. These studs enhance traction on icy surfaces. Longer spikes. The spikes are surrounded by v shaped segments fit into grooved rods called wear rods under each snowmobile aluminum. 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): HVAF Process". Journal of Thermal Spray Technology 7 (2): 515. doi:10.1111/j.1151 2916.1989.tb06169.x (http://dx.doi.org 213–218. doi:10.1361/105996398770350954 (http://dx.doi.org /10.1111%2Fj.1151 2916.1989.tb06169.x). /10.1361%2F105996398770350954). 2. ^ a b Elastic Properties and Young Modulus for some Materials 7. ^ Nerz, J.; B. Kushner; A. Rotolico (1992). "Microstructural (http://www.engineeringtoolbox.com/young modulus d_417.html) evaluation of tungsten carbide cobalt coatings". Journal of 3. ^ a b c d e f Pierson, Hugh O. (1992). Handbook of Chemical Thermal Spray Technology 1 (2): 147–152. Vapor Deposition (CVD): Principles, Technology, and doi:10.1007/BF02659015 (http://dx.doi.org Applications . William Andrew Inc. ISBN 0 8155 1300 3. /10.1007%2FBF02659015). 4. ^ Lackner, A. and Filzwieser A. "Gas carburizing of tungsten 8. ^ Noritaka Mizuno, Hitoshi Nakajima; Tetsuichi Kudo (1999). carbide (WC) powder" U.S. Patent 6,447,742 "Reaction of Metal, Carbide, and Nitride of Tungsten with (http://www.google.com/patents/US6447742) (2002) Hydrogen Peroxide Characterized by 183W Nuclear Magnetic 5. ^ Zhong, Y.; et al. (2011). "A study on the synthesis of Resonance and Raman Spectroscopy". Chemistry of Materials nanostructured WC–10 wt% Co particles from WO3, Co3O4, 11 (3): 691–697. doi:10.1021/cm980544o (http://dx.doi.org and graphite". Journal of Materials Science 46 (19): 6323. /10.1021%2Fcm980544o). doi:10.1007/s10853 010 4937 y (http://dx.doi.org 9. ^ Pohanish, Richard P. (2012). Sittig's Handbook of Toxic and /10.1007%2Fs10853 010 4937 y). Hazardous Chemicals and Carcinogens
4 of 6 26/10/2013 2:53 PM Tungsten carbide - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Tungsten_carbide
(http://books.google.com/books?id=RYt0Wzb60b4C& 24. ^ Davis, Joseph R., ASM International. Handbook Committee pg=PA2670). Sixth Edition. Kidlington, UK: Elsevier, Inc. (1995). Tool materials (http://books.google.com p. 2670. ISBN 978 1 4377 7869 4. /books?id=Kws7x68r_aUC&pg=PA289). ASM International. 10. ^ "Material: Tungsten Carbide (WC), bulk" pp. 289–. ISBN 978 0 87170 545 7. (http://www.memsnet.org/material/tungstencarbidewcbulk/). 25. ^ Ford, Roger (2000). Germany's Secret Weapons in World MEMSnet. Retrieved 3 April 2013. War II (http://books.google.com/books?id=lU8xBhe9ntsC& 11. ^ a b Roylance, David. "Material Properties" (http://web.mit.edu pg=PA125). Zenith Imprint. pp. 125–. ISBN 978 0 7603 0847 9. /course/3/3.11/www/modules/props.pdf). Massachusetts Institute 26. ^ Zaloga, Steven J. (2005). US Tank and Tank Destroyer of Technology. Retrieved 4 April 2013. Battalions in the ETO 1944–45 (http://books.google.com 12. ^ CRC Materials Science and Engineering Handbook (2001). /books?id=sCdlGIbmHjoC&pg=PA37). Osprey Publishing. 13. ^ Lalena, John N.; Cleary, David A. (2010). Principles of pp. 37–. ISBN 978 1 84176 798 7. Inorganic Materials Design (http://books.google.com 27. ^ Green, Michael and Stewart, Greg (2005). M1 Abrams at War /books?id=FhZwYudTCsQC&pg=PA422) (Second ed.). (http://books.google.com/books?id=M1P6jT8_yrgC&pg=PA66). Hoboken, New Jersey: John Wiley & Sons, Inc. p. 422. Zenith Imprint. pp. 66–. ISBN 978 0 7603 2153 9. ISBN 978 0 470 40403 4. 28. ^ Tucker, Spencer (2004). Tanks: an illustrated history of their 14. ^ CRC Materials Science and Engineering Handbook, p.405 impact (http://books.google.com/books?id=N481TmqiSiUC& 15. ^ "Velocity of Sound in Various Media" (http://www.rfcafe.com pg=PA348). ABC CLIO. pp. 348–. ISBN 978 1 57607 995 9. /references/general/velocity sound media.htm). RF Cafe. 29. ^ Connally, Craig (2004). The mountaineering handbook: Retrieved 4 April 2013. modern tools and techniques that will take you to the top 16. ^ Kittel, Charles (1995). Introduction to Solid State Physics (7 (http://books.google.com/books?id=c0MUESWJo2oC& ed.). Wiley India. ISBN 81 265 1045 5. pg=PA14). McGraw Hill Professional. pp. 14–. a b 17. ^ Ettmayer, Peter; Walter Lengauer (1994). Carbides: ISBN 978 0 07 143010 4. transition metal solid state chemistry encyclopedia of inorganic 30. ^ Hermance, Richard (2006). Snowmobile and ATV accident chemistry . John Wiley & Sons. ISBN 0 471 93620 0. investigation and reconstruction (http://books.google.com a b 18. ^ Wells, A. F. (1984). Structural Inorganic Chemistry (5 /books?id= msCn1jK8z8C&pg=PA13). Lawyers & Judges ed.). Oxford Science Publications. ISBN 0 19 855370 6. Publishing Company. pp. 13–. ISBN 978 0 913875 02 5. 19. ^ Sara, R. V. (1965). "Phase Equilibria in the System Tungsten 31. ^ Hamp, Ron; Gorr, Eric and Cameron, Kevin (2011). —Carbon". Journal of the American Ceramic Society 48 (5): Four-Stroke Motocross and Off-Road Performance Handbook 251–257. doi:10.1111/j.1151 2916.1965.tb14731.x (http://books.google.com/books?id=24kHuJV2LcAC&pg=PA69). (http://dx.doi.org/10.1111%2Fj.1151 2916.1965.tb14731.x). MotorBooks International. pp. 69–. ISBN 978 0 7603 4000 4. 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). 33. ^ Breningstall, F. Thomas. "Winter shoes" 21. ^ Kleinhenz, Sven; Valérie Pfennig; Konrad Seppelt (1998). (http://www.wiwfarm.com/wntrs.htm). Windt im Wald Farm.
"Preparation and Structures of [W(CH 3)6], [Re(CH 3)6], Retrieved July 2011. − − [Nb(CH 3)6] , and [Ta(CH 3)6] ". Chemistry—A European 34. ^ Reichert, Marimargaret and Young, Jack H. (1997). Journal 4 (9): 1687–91. Sterilization technology for the health care facility doi:10.1002/(SICI)1521 3765(19980904)4:9<1687::AID (http://books.google.com/books?id=HDzcboqJR9kC&pg=PA30). CHEM1687>3.0.CO;2 R (http://dx.doi.org/10.1002 Jones & Bartlett Learning. pp. 30–. ISBN 978 0 8342 0838 4. %2F%28SICI%291521 3765%2819980904%294%3A9%3C168 35. ^ Breaking Tungsten Carbide (http://cherylkremkow.com 7%3A%3AAID CHEM1687%3E3.0.CO%3B2 R). /the new luxury/breaking tungsten carbide/). 22. ^ Sickafoose, S.M.; A.W. Smith; M. D. Morse (2002). "Optical cherylkremkow.com (2009 10 29) spectroscopy of tungsten carbide (WC)". J. Chem. Phys. 116 36. ^ Tungsten Carbide Manufacturing (3): 993. doi:10.1063/1.1427068 (http://dx.doi.org (http://www.forevermetals.com/jewelry tungsten carbide ring/). /10.1063%2F1.1427068). forevermetals.com (2005 06 18) 23. ^ Rao (2009). Manufacturing Technology Vol-Ii 2E 37. ^ "How does a ballpoint pen work?" (http://books.google.com/books?id=3sS5a4jqzS8C&pg=PA30). (http://science.howstuffworks.com/question683.htm). Tata McGraw Hill Education. pp. 30–. ISBN 978 0 07 008769 9. Engineering . HowStuffWorks. 1998 2007. Retrieved 2007 11 16.
5 of 6 26/10/2013 2:53 PM Tungsten carbide - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Tungsten_carbide
38. ^ "Wolfram Martin Simpson Signature Slide" communication". Catalysis Letters 45 : 1–2. (http://www.wolframslides.com/mssig.php). Wolfram Slides . doi:10.1023/A:1019059410876 (http://dx.doi.org Retrieved 6 August 2013. /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. Djéga (//www.ncbi.nlm.nih.gov/pubmed/6434250). Mariadassou; (1997). "Nitride and carbide of molybdenum and 42. ^ "12th Report on Carcinogens" (http://ntp.niehs.nih.gov tungsten as substitutes of iridium for the catalysts used for space /go/roc12). National Toxicology Program. Retrieved 2011 06 24.
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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