Editing Refractory metals (section)

==Applications==

Refractory metals, and alloys made from them, are used in [[lighting]], tools, [[lubricant]]s, [[nuclear reaction]] [[control rod]]s, as [[catalyst]]s, and for their [[chemical]] or electrical properties.  Because of their high [[melting point|melting points]], refractory metal components are never fabricated by [[Casting (metalworking)|casting]].  The process of [[powder metallurgy]] is used: powders of the pure metal are compacted, heated using electric current, and further fabricated by cold working with annealing steps.  Refractory metals and their alloys can be worked into [[wire]], [[ingot]]s, [[rebar]]s, [[Sheet metal|sheets]], or [[foil (metal)|foil]].

===Molybdenum alloys===
{{main|Molybdenum|Molybdenum#Applications}}
Molybdenum-based alloys are widely used, because they are cheaper than superior tungsten alloys. The most widely used alloy of molybdenum is the [[titanium|'''T'''itanium]]-[[zirconium|'''Z'''irconium]]-'''M'''olybdenum alloy TZM, composed of 0.5% titanium and 0.08% of zirconium (with molybdenum being the rest). The alloy exhibits a higher creep resistance and strength at high temperatures, making service temperatures of above 1060&nbsp;°C possible for the material. The high resistivity of Mo-30W, an alloy of 70% molybdenum and 30% tungsten, against the attack of molten [[zinc]] makes it the ideal material for casting zinc. It is also used to construct valves for molten zinc.<ref>{{cite book | last=Smallwood | first=Robert E. | title=ASTM special technical publication 849: Refractory metals and their industrial applications: a symposium |chapter-url=https://books.google.com/books?id=agaacIr25KcC&pg=PA9 | year=1984 | publisher=ASTM International | isbn=978-0-8031-0203-3 |page=9 |chapter=TZM Moly Alloy}}</ref>

Molybdenum is used in [[Relay#Mercury-wetted relay|mercury-wetted reed relays]], because molybdenum does not form [[Amalgam (chemistry)|amalgams]] and is therefore resistant to corrosion by liquid [[Mercury (element)|mercury]].<ref>{{cite journal | title = Corrosion Resistance of Molybdenum in Mercury| doi = 10.1023/A:1024903616630 | year = 2003 | last1 = Kozbagarova | first1 = G. A. | last2 = Musina | first2 = A. S. | last3 = Mikhaleva | first3 = V. A. | journal = Protection of Metals | volume = 39 | pages = 374–6 | issue = 4| s2cid = 91428385 }}</ref><ref>{{cite book | last=Gupta | first=C. K. | title=Extractive Metallurgy of Molybdenum | chapter-url=https://books.google.com/books?id=6V7oPjy_0IwC&pg=PA49 | year=1992 | publisher=CRC Press | isbn = 978-0-8493-4758-0 |pages=48–49 |chapter=Electric and Electronic Industry}}</ref>

Molybdenum is the most commonly used of the refractory metals.  Its most important use is as a strengthening [[alloy]] of [[steel]].  [[Hollow structural section|Structural tubing]] and [[piping]] often contains molybdenum, as do many [[stainless steel]]s.  Its strength at high temperatures, resistance to wear, and low [[coefficient of friction]] are all properties which make it invaluable as an alloying compound.  Its excellent anti-[[friction]] properties lead to its incorporation in [[Grease (lubricant)|greases]] and [[oil]]s where reliability and performance are critical.  Automotive [[constant-velocity joint]]s use grease containing molybdenum.  The compound sticks readily to metal and forms a very hard, friction-resistant coating.  Most of the world's molybdenum [[ore]] can be found in China, the [[United States|USA]], Chile, and [[Canada]].<ref name="USGSCS2008">{{cite web |url = http://minerals.usgs.gov/minerals/pubs/commodity/molybdenum/mcs-2009-molyb.pdf |title = Commodity Summary 2009:Molybdenum |first = Michael J. |last=Magyar |publisher = [[United States Geological Survey]] |access-date = 2010-04-01}}</ref><ref>{{cite journal | doi =10.1016/0025-5416(88)90529-0 | title =Structure and properties of high energy, high rate consolidated molybdenum alloy TZM | year =1988 | last1 =Ervin | first1 =D. R. | last2 =Bourell | first2 =D. L. | last3 =Persad | first3 =C. | last4 =Rabenberg | first4 =L. | journal =Materials Science and Engineering: A | volume =102 | pages =25–30}}</ref><ref>{{cite book |last=Oleg D. |first=Neikov |title=Handbook of Non-Ferrous Metal Powders: Technologies and Applications |chapter-url=https://books.google.com/books?id=6aP3te2hGuQC&pg=PA465 |year=2009 |publisher=Elsevier |isbn=978-1-85617-422-0 |pages=464–6 |chapter=Properties of Molybdenum and Molybdenum Alloys powder}}</ref><ref>{{cite book |last=Davis |first=Joseph R. |title= ASM specialty handbook: Heat-resistant materials |chapter-url=https://books.google.com/books?id=GEHA8_bix0oC&pg=PA361 |year=1997 |isbn=978-0-87170-596-9 |pages=361–382 |chapter=Refractory Metalls and Alloys |publisher=ASM International }}</ref><!--https://books.google.com/books?id=IzqsAAAAIAAJ&pg=PA396-->

===Tungsten and its alloys===
{{main|Tungsten|Tungsten#Applications}}
Tungsten was discovered in 1781 by [[Sweden|Swedish]] chemist [[Carl Wilhelm Scheele]]. Tungsten has the highest melting point of all metals, at {{convert|3410|°C|°F|0|lk=on}}.
[[File:filament.jpg|thumb|[[Electric filament|Filament]] of a 200 watt incandescent lightbulb highly magnified]]
Up to 22% [[Rhenium]] is alloyed with tungsten to improve its high-temperature strength and corrosion resistance. [[Thorium]] as an alloying compound is used when electric arcs have to be established: ignition is easier and the arc burns more stably than without the addition of thorium. For powder metallurgy applications, binders have to be used for the sintering process. For the production of tungsten heavy alloys, binder mixtures of [[nickel]] and [[iron]] or nickel and [[copper]] are widely used. The tungsten content of the alloy is normally above 90%. The diffusion of the binder elements into the tungsten grains is low even at the [[sintering]] temperatures and therefore the interior of the grains are pure tungsten.<ref>{{cite book | isbn = 978-0-306-45053-2 | url = https://books.google.com/books?id=foLRISkt9gcC&pg=PA1 | title = Tungsten: properties, chemistry, technology of the element, alloys, and chemical compounds | first1 = Erik | last1 = Lassner | publisher = Springer | year = 1999 | first2 = Wolf-Dieter | last2 =Schubert | pages =255–282}}</ref>

Tungsten and its alloys are often used in applications where high temperatures are present but a high strength is still necessary and the high density is not troublesome.<ref name="W-Trend">{{cite book |url = https://books.google.com/books?id=1T8rAAAAYAAJ&pg=PA1| title = Trends in Usage of Tungsten: Report |publisher = National Academy of Sciences-National Academy of Engineering |author = ((National Research Council (U.S.), Panel on Tungsten, Committee on Technical Aspects of Critical and Strategic Material)) |year = 1973 |pages = 1–3}}</ref> Tungsten-wire filaments provide the vast majority of household [[incandescent lighting]], but are also common in industrial lighting as electrodes in arc lamps. Lamps get more efficient in the conversion of electric energy to light with higher temperatures, so a high melting point is essential for the application as filament in incandescent light.<ref name="tungst">{{cite book | isbn = 978-0-306-45053-2 | url = https://books.google.com/books?id=foLRISkt9gcC | title = Tungsten: properties, chemistry, technology of the element, alloys, and chemical compounds | first1 = Erik | last1 = Lassner | publisher = Springer | year = 1999 | first2 = Wolf-Dieter | last2 =Schubert}}</ref>  [[Gas tungsten arc welding]] (GTAW, also known as tungsten inert gas (TIG) welding) equipment uses a permanent, non-melting [[electrode]]. The high melting point and the wear resistance against the electric arc makes tungsten a suitable material for the  electrode.<ref>{{cite book | chapter-url = https://books.google.com/books?id=gScGxzDhTeQC&pg=PA28 | title = Welding health and safety: a field guide for OEHS professionals | first =Michael K. | last = Harris | isbn = 978-1-931504-28-7 | publisher = AIHA | year =2002 | chapter = Welding Health and Safety | page = 28}}</ref><ref>{{cite book | publisher = Industrial Press | year = 2001 | isbn = 978-0-8311-3151-7 | title = Welding essentials: questions & answers | first1 =William L. | last1 =Galvery | first2 =Frank M. | last2 =Marlow | url = https://archive.org/details/weldingessential0000galv | url-access = registration| page = [https://archive.org/details/weldingessential0000galv/page/185 185]}}</ref>

Tungsten's high density and strength are also key properties for its use in weapon [[projectile]]s, for example as an alternative to [[depleted uranium]] for tank gun rounds.<ref>{{cite conference | url = http://aux.ciar.org/ttk/mbt/papers/symp_19/TB191191.pdf | conference= 19th International Symposium of Ballistics | date = 7–11 May 2001 | place = Interlaken, Switzerland | title = KINETIC ENERGY PROJECTILES: DEVELOPMENT HISTORY, STATE OF THE ART, TRENDS | first1 = W. | last1 = Lanz| first2 =  W. | last2= Odermatt| first3 = G. | last3= Weihrauch3}}</ref>  Its high melting point makes tungsten a good material for applications like [[Rocket engine nozzle|rocket nozzles]], for example in the [[UGM-27 Polaris]].<ref>{{cite book | page = 38 | chapter-url = https://books.google.com/books?id=9n-rX13bNsAC&pg=PA38| chapter = Powder metallurgyfor Aerospace Applications | isbn = 978-81-224-2030-2 | title = Powder metallurgy : processing for automotive, electrical/electronic and engineering industry| first = P. | last = Ramakrishnan | publisher = New Age International | date = 2007-01-01}}</ref> Some of the applications of tungsten are not related to its refractory properties but simply to its density. For example, it is used in balance weights for planes and helicopters or for heads of [[Golf club (equipment)|golf clubs]].<ref>{{cite journal |title = Tungsten Heavy Alloy For Defence Applications | last1 = Arora |first1=Arran |last2=Venu Gopal Rao | journal = Materials Technology | volume = 19 | issue = 4 | pages = 210–6 | year = 2004 |doi=10.1080/10667857.2004.11753087| bibcode = 2004MaTec..19..210A | s2cid = 139045633 }}</ref><ref>{{cite journal | doi = 10.1007/s11837-001-0147-z| title =Fabricating sports equipment components via powder metallurgy | year = 2001 | last1 = Moxson | first1 = V. S. | last2 = (sam) Froes | first2 = F. H. | journal = JOM | volume = 53 | pages = 39 |bibcode = 2001JOM....53d..39M | issue = 4 | s2cid =135653323 }}</ref> In these applications, similar dense materials like the more expensive [[osmium]] can also be used.

The most common use for tungsten is as the compound [[tungsten carbide]] in [[drill bit]]s, machining and cutting tools. The largest reserves of tungsten are in [[China]], with deposits in [[Korea]], [[Bolivia]], [[Australia]], and other countries.

It also finds itself serving as a [[lubrication|lubricant]], [[antioxidant]], in nozzles and bushings, as a protective coating, and in many other ways.  Tungsten can be found in printing inks, [[x-ray]] screens, in the processing of [[petroleum]] products, and flame proofing of [[textile]]s.

===Niobium alloys===
{{main|Niobium#Applications|Niobium alloy}}
[[File:Apollo CSM lunar orbit.jpg|thumb|Apollo CSM with the dark rocket nozzle made from niobium-titanium alloy |alt=Image of the Apollo Service Module with the moon in the background]]
Niobium is nearly always found together with tantalum, and was named after [[Niobe]], the daughter of the [[Greek mythology|mythical]] [[Greece|Greek]] king [[Tantalus]] for whom tantalum was named.  Niobium has many uses, some of which it shares with other refractory metals.  It is unique in that it can be worked through annealing to achieve a wide range of strength and [[Elasticity (physics)|ductility]], and is the least dense of the refractory metals. It can also be found in [[electrolytic capacitor]]s and in the most practical [[Superconductivity|superconducting]] alloys.  Niobium can be found in [[aircraft]] [[gas turbine]]s, [[vacuum tube]]s, and [[nuclear reactor]]s.

An alloy used for [[liquid rocket]] thruster nozzles, such as in the main engine of the [[Apollo Lunar Module]]s, is C103, which consists of 89% niobium, 10% hafnium and 1% titanium.<ref name="hightemp">{{cite journal |url = http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_3/images/pdfs/016.pdf |title = Niobium alloys and high Temperature Applications |first = John |last = Hebda |journal = Niobium Science & Technology: Proceedings of the International Symposium Niobium 2001 (Orlando, Florida, USA) |publisher = Companhia Brasileira de Metalurgia e Mineração |date = 2001-05-02 |url-status = dead |archive-url = https://web.archive.org/web/20081217080513/http://www.cbmm.com.br/portug/sources/techlib/science_techno/table_content/sub_3/images/pdfs/016.pdf |archive-date = 2008-12-17 }}</ref> Another [[niobium alloy]] was used for the nozzle of the [[Apollo Command/Service Module#Service Module (SM)|Apollo Service Module]]. As niobium is oxidized at temperatures above 400&nbsp;°C, a protective coating is necessary for these applications to prevent the alloy from becoming brittle.<ref name ="hightemp"/>

===Tantalum and its alloys===
{{main|Tantalum|Tantalum#Applications}}
Tantalum is one of the most [[corrosion]]-resistant substances available.  Many important uses have been found for tantalum owing to this property, particularly in the [[medicine|medical]] and [[surgery|surgical]] fields, and also in harsh [[acid]]ic environments.  It is also used to make superior electrolytic capacitors.  Tantalum films provide the second most [[capacitance]] per volume of any substance after [[Aerogel]],{{Citation needed|date=July 2009}} and allow [[miniaturization]] of [[electronic component]]s and [[electrical network|circuitry]]. Many [[mobile phone|cellular phone]]s and [[computer]]s contain tantalum capacitors.

===Rhenium alloys===
{{main|Rhenium}}
Rhenium is the most recently discovered refractory metal.  It is found in low concentrations with many other metals, in the ores of other refractory metals, [[platinum]] or [[copper]] ores.  It is useful as an alloy to other refractory metals, where it adds [[ductility]] and [[tensile strength]]. Rhenium alloys are used in electronic components, [[gyroscope]]s and [[nuclear reactor]]s.  Rhenium finds its most important use as a catalyst.  It is used as a catalyst in reactions such as [[alkylation]], [[dealkylation]], [[hydrogenation]] and [[oxidation]].  However, its rarity makes it the most expensive of the refractory metals.<ref>{{cite book | chapter-url = https://books.google.com/books?id=IzqsAAAAIAAJ&pg=PR208 | title = Behavior and Properties of Refractory Metals | first = J. W. | last = Wilson | publisher = Stanford University Press | year = 1965 | isbn = 978-0-8047-0162-4 | chapter = Rhenium}}</ref>