{{Short description|Compound of iron and carbon}}{{chembox| verifiedrevid = | Name = Iron carbide| ImageFile = Iron carbide.jpg| ImageCaption = Iron carbide plates | ImageFile1 = Kristallstruktur Zementit.png| ImageName1 =Orthorhombic Fe3C. Iron atoms are blue| IUPACName = Iron carbide| OtherNames = Cementite|Section1={{Chembox Identifiers

correct|chemspider}}| ChemSpiderID = | EINECS = 234-566-7| SMILES = [C].[Fe].[Fe].[Fe]| InChIKey = | StdInChI=1S/C.3Fe| StdInChIKey = TXAHJXBWFZQNQY-UHFFFAOYSA-N

correct|CAS}}| CASNo = 12011-67-5

correct|FDA}}| UNII = | PubChem = }}|Section2={{Chembox Properties| Formula = Fe3C| MolarMass = 179.546 g/mol| Appearance = dark gray or black crystals, odorless| Density = 7.694 g/cm3, solidHaynes, p. 4.67| Solubility = insoluble| MeltingPtC = 1227| MeltingPt_ref = | pKa =}}|Section3={{Chembox Structure

YEAR=1964

FIRST1=F. H.

FIRST2=J.

VOLUME=17

PAGES=1331â€“1332

BIBCODE=1964ACCRY..17.1331H, | MolShape = | Coordination =

Orthorhombic crystal system> Orthorhombic, oP16| SpaceGroup = Pnma, No. 62| LattConst_a = 0.509 nm| LattConst_b = 0.6478 nm| LattConst_c = 0.4523 nm| UnitCellFormulas = 4| Dipole =}}| Section4 = {{Chembox Thermochemistry| Thermochemistry_ref =Haynes, p. 5.23| HeatCapacity = 105.9 JÂ·molâˆ’1Â·Kâˆ’1| Entropy = 104.6 JÂ·molâˆ’1Â·Kâˆ’1| DeltaHform = 25.1 kJÂ·molâˆ’1| DeltaGfree = 20.1 kJÂ·molâˆ’1| DeltaHcombust =| DeltaHfus =| DeltaHvap =}}|Section7={{Chembox Hazards| ExternalSDS = | MainHazards = }}|Section8={{Chembox Related| OtherAnions =| OtherCations =| OtherCompounds = }}}}Cementite (or iron carbide) is a compound of iron and carbon, more precisely an intermediate transition metal carbide with the formula Fe3C. By weight, it is 6.67% carbon and 93.3% iron. It has an orthorhombic crystal structure.{{harvnb|Smith|Hashemi|2006|p=363}} It is a hard, brittle material, normally classified as a ceramic in its pure form, and is a frequently found and important constituent in ferrous metallurgy. While cementite is present in most steelsBOOK, Verhoeven, John D., Steel Metallurgy for the Non-Metallurgist, 2007, ASM International, 978-1-61503-056-9, 35,books.google.com/books?id=brpx-LtdCLYC&pg=PA35, en, and cast irons, it is produced as a raw material in the iron carbide process, which belongs to the family of alternative ironmaking technologies. The name cementite originated from the theory of Floris Osmond and J. Werth, in which the structure of solidified steel consists of a kind of cellular tissue, with ferrite as the nucleus and Fe3C the envelope of the cells. The carbide therefore cemented the iron.

Metallurgy

In the ironâ€“carbon system (i.e. plain-carbon steels and cast irons) it is a common constituent because ferrite can contain at most 0.02wt% of uncombined carbon.JOURNAL,www.researchgate.net/publication/277605401, Cementite Formation from Hematiteâ€“Graphite Mixture by Simultaneous Thermalâ€“Mechanical Activation, Metallurgical and Materials Transactions B, 46, 2, 813â€“823, 10.1007/s11663-014-0228-3, Ashrafzadeh, Milad, Soleymani, Amir Peyman, Panjepour, Masoud, Shamanian, Morteza, 2015, 2015MMTB...46..813A, 98253213, Therefore, in carbon steels and cast irons that are slowly cooled, a portion of the carbon is in the form of cementite.{{harvnb|Smith|Hashemi|2006|pp=366â€“372}} Cementite forms directly from the melt in the case of white cast iron. In carbon steel, cementite precipitates from austenite as austenite transforms to ferrite on slow cooling, or from martensite during tempering. An intimate mixture with ferrite, the other product of austenite, forms a lamellar structure called pearlite.(File:Iron carbon phase diagram.svg|thumb|left|The iron-carbon phase diagram)While cementite is thermodynamically unstable, eventually being converted to austenite (low carbon level) and graphite (high carbon level) at higher temperatures, it does not decompose on heating at temperatures below the eutectoid temperature (723 Â°C) on the metastable iron-carbon phase diagram.Mechanical properties are as follows: room temperature microhardness 760â€“1350 HV; bending strength 4.6â€“8 GPa, Young’s modulus 160â€“180 GPa, indentation fracture toughness 1.5â€“2.7 MPaâˆšm.JOURNAL, Bhadeshia, H. K. D. H., 2020, Cementite, International Materials Reviews, 10.1080/09506608.2018.1560984, 65, 1, 1â€“27, 2020IMRv...65....1B, free,

Pure form

{{Steels}}Cementite changes from ferromagnetic to paramagnetic upon heating to its Curie temperature of approximately {{convert|480|K|C}}.JOURNAL,zenodo.org/record/1431493, Smith, S.W.J., White, W., Barker, S.G., The Magnetic Transition Temperature of Cementite, Proc. Phys. Soc. Lond., 24, 1, 62â€“69, 1911, 10.1088/1478-7814/24/1/310, 1911PPSL...24...62S, A natural iron carbide (containing minor amounts of nickel and cobalt) occurs in iron meteorites and is called cohenite after the German mineralogist Emil Cohen, who first described it.Buchwald, Vagn F. (1975) Handbook of Iron Meteorites, University of California Press

Other iron carbides

There are other forms of metastable iron carbides that have been identified in tempered steel and in the industrial Fischerâ€“Tropsch process. These include epsilon (Îµ) carbide, hexagonal close-packed Fe2â€“3C, precipitates in plain-carbon steels of carbon content > 0.2%, tempered at 100â€“200 Â°C. Non-stoichiometric Îµ-carbide dissolves above ~200 Â°C, where HÃ¤gg carbides and cementite begin to form. HÃ¤gg carbide, monoclinic Fe5C2, precipitates in hardened tool steels tempered at 200â€“300 Â°C.JOURNAL, 10.1524/zkri.1934.89.1.92, HÃ¤gg, Gunnar, Pulverphotogramme eines neuen Eisencarbides, Zeitschrift fÃ¼r Kristallographie - Crystalline Materials, 1934, 89, 1â€“6, 92â€“94, 100657250, BOOK, Smith, William F., Structure and properties of engineering alloys, 1981, McGraw-Hill, New York, 978-0-07-0585607, 61â€“62, It has also been found naturally as the mineral Edscottite in the Wedderburn meteoriteWEB,www.theage.com.au/national/victoria/this-meteorite-came-from-the-core-of-another-planet-inside-it-a-new-mineral-20190830-p52mhg.html, This meteorite came from the core of another planet. Inside it, a new mineral, Mannix, Liam, 2019-08-31, The Age, 2019-09-14,

References

Bibliography

BOOK, Haynes, Haynes, William M., 2016, CRC Handbook of Chemistry and Physics, 97th, CRC Press, 9781498754293,
BOOK, Smith, William F., Hashemi, Javad, Foundations of Materials Science and Engineering, 4th, 2006, McGraw-Hill, 978-0-07-295358-9,

External links

cst-www.nrl.navy.mil/lattice/struk/d0_11.html" title="web.archive.org/web/20090512154354cst-www.nrl.navy.mil/lattice/struk/d0_11.html">Crystal structure of cementite at NRL
JOURNAL, Hallstedt, Bengt, Djurovic, Dejan, von Appen, JÃ¶rg, Dronskowski, Richard, Dick, Alexey, KÃ¶rmann, Fritz, Hickel, Tilmann, Neugebauer, JÃ¶rg, Thermodynamic properties of cementite (Fe3C), Calphad, March 2010, 34, 1, 129â€“133, 10.1016/j.calphad.2010.01.004,
JOURNAL, Le Caer, G., Dubois, J. M., Pijolat, M., Perrichon, V., Bussiere, P., Characterization by Moessbauer spectroscopy of iron carbides formed by Fischerâ€“Tropsch synthesis, The Journal of Physical Chemistry, November 1982, 86, 24, 4799â€“4808, 10.1021/j100221a030,
JOURNAL, Bauer-Grosse, E., Frantz, C., Le Caer, G., Heiman, N., Formation of Fe7C3 and Fe5C2 type metastable carbides during the crystallization of an amorphous Fe75C25 alloy, Journal of Non-Crystalline Solids, June 1981, 44, 2â€“3, 277â€“286, 10.1016/0022-3093(81)90030-2, 1981JNCS...44..277B,

- content above as imported from Wikipedia
- "cementite" does not exist on GetWiki (yet)
- time: 4:42am EDT - Wed, May 22 2024

[ this remote article is provided by Wikipedia ]

CONNECT