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{{Short description|Steel known for strength and toughness}}
{{Steels}}
'''Maraging steels''' (a [[portmanteau]] of "[[martensitic]]" and "aging") are [[steel]]s that are known for possessing superior strength and toughness without losing [[ductility]]. ''Aging'' refers to the extended heat-treatment process. These steels are a special class of very-low-[[carbon]] ultra-high-strength steels that derive their strength not from carbon, but from [[precipitation hardening|precipitation]] of [[intermetallic]] compounds. The principal alloying element is 15 to 25 [[Mass fraction (chemistry)#Mass percentage|wt%]] [[nickel]].<ref name=degarmo>{{citation|last1=Degarmo|first1=E. Paul|last2=Black|first2 =J. T.|last3=Kohser|first3=Ronald A.|title=Materials and Processes in Manufacturing|publisher=Wiley|page=119|year=2003|edition=9th|isbn=0-471-65653-4}}</ref> Secondary alloying elements, which include [[cobalt]], [[molybdenum]] and [[titanium]], are added to produce intermetallic [[precipitates]].<ref name=degarmo/
Original development by Clarence Gieger Bieber of [[Vale Canada|Inco]] in the late 1950s was carried out on 20 and 25 wt% Ni steels to which small additions of [[aluminium]], titanium, and [[niobium]] were made.<ref>{{US patent|3093518}}</ref> A rise in the price of cobalt in the late 1970s led to the development of cobalt-free maraging steels.<ref name="sha-guo">{{cite book | title=Maraging Steels: Modelling of Microstructure, Properties and Applications | first1=W | first2=Z | last1=Sha | last2=Guo | publisher=Elsevier | date=2009-10-26}}</ref>
The common, non-stainless grades contain 17–19 wt% nickel, 8–12 wt% cobalt, 3–5 wt% molybdenum and 0.2–1.6 wt% titanium. Addition of chromium produces stainless grades resistant to corrosion. This also indirectly increases [[hardenability]] as they require less nickel; high-chromium, high-nickel steels are generally [[austenite|austenitic]] and unable to transform to [[martensite]] when heat treated, while lower-nickel steels can transform to martensite. Alternative variants of nickel-reduced maraging steels are based on alloys of iron and manganese plus minor additions of aluminium, nickel and titanium where compositions between Fe-9wt% Mn to Fe-15wt% Mn have been used.<ref name=maraging2>{{citation|last1= Raabe|first1=D.|last2= Sandlöbes|first2 =S.|last3= Millan|first3=J. J.|last4=Ponge|first4=D.|last5=Assadi|first5=H.|last6=Herbig|first6=M.|last7=Choi|first7=P.P.| title= Segregation engineering enables nanoscale martensite to austenite phase transformation at grain boundaries: A pathway to ductile martensite▼
▲The common, non-stainless grades contain 17–19 wt% nickel, 8–12 wt% cobalt, 3–5 wt% molybdenum and 0.2–1.6 wt% titanium.<ref>{{cite web |last1=INCO |title=18% Nickel Maraging Steel – Engineering Properties |url=https://nickelinstitute.org/en/library/technical-guides/18-nickel-maraging-steel-engineering-properties-4419/ |website=Nickel Institute}}</ref> Addition of chromium produces stainless grades resistant to corrosion. This also indirectly increases [[hardenability]] as they require less nickel; high-chromium, high-nickel steels are generally [[austenite|austenitic]] and unable to transform to [[martensite]] when heat treated, while lower-nickel steels can transform to martensite. Alternative variants of nickel-reduced maraging steels are based on alloys of iron and manganese plus minor additions of aluminium, nickel and titanium where compositions between Fe-9wt% Mn to Fe-15wt% Mn have been used.<ref name=maraging2>{{citation|last1= Raabe|first1=D.|last2= Sandlöbes|first2 =S.|last3= Millan|first3=J. J.|last4=Ponge|first4=D.|last5=Assadi|first5=H.|last6=Herbig|first6=M.|last7=Choi|first7=P.P.| title= Segregation engineering enables nanoscale martensite to austenite phase transformation at grain boundaries: A pathway to ductile martensite
|journal= Acta Materialia|pages=6132–6152|year=2013|volume=61 |issue=16|doi=10.1016/j.actamat.2013.06.055|bibcode=2013AcMat..61.6132R}}.</ref> The manganese has a similar effect as nickel, i.e. it stabilizes the austenite phase. Hence, depending on their manganese content, Fe-Mn maraging steels can be fully martensitic after quenching them from the high temperature austenite phase or they can contain retained austenite.<ref name=tripmar2>{{citation|last1= Dmitrieva|first1=O.|last2=Ponge|first2 =D.|last3= Inden|first3=G. |last4= Millan|first4=J.|last5= Choi|first5=P. |last6= Sietsma|first6=J. |last7= Raabe|first7=D.|title= Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation|journal= Acta Materialia|year=2011|volume=59|issue=1|pages=364–374|doi= 10.1016/j.actamat.2010.09.042|issn=1359-6454|arxiv=1402.0232|bibcode=2011AcMat..59..364D|s2cid=13781776}}</ref> The latter effect enables the design of maraging-TRIP steels where TRIP stands for Transformation-Induced-Plasticity.<ref name=tripmar>{{citation|last1= Raabe|first1=D.|last2=Ponge|first2 =D.|last3= Dmitrieva|first3=O. |last4= Sander|first4=B.|title= Nano-precipitate hardened 1.5 GPa steels with unexpected high ductility|journal= Scripta Materialia|page=1141|year=2009|volume=60|issue=12|doi=10.1016/j.scriptamat.2009.02.062 }}</ref>
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==Grades of maraging steel==
Maraging steels are usually described by a number (e.g., [[SAE steel grades]] 200, 250, 300 or 350), which indicates the approximate nominal tensile strength in thousands of pounds per square inch (ksi); the compositions and required properties are defined in [[United States Military Standard|US military standard]] MIL-S-46850D.<ref name=STD46850D>Military Specification 46850D: STEEL : BAR, PLATE, SHEET, STRIP, FORGINGS, AND EXTRUSIONS, 18 PERCENT NICKEL ALLOY, MARAGING, 200 KSI, 250 KSI, 300 KSI, AND 350 KSI, HIGH QUALITY, available from http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-S/MIL-S-46850D_19899/</ref> The higher grades have more cobalt and titanium in the alloy; the compositions below are taken from table 1 of MIL-S-46850D:▼
▲Maraging steels are usually described by a number (e.g., [[SAE steel grades]] 200, 250, 300 or 350), which indicates the approximate nominal tensile strength in thousands of pounds per square inch; the compositions and required properties are defined in [[United States Military Standard|US military standard]] MIL-S-46850D.<ref name=STD46850D>Military Specification 46850D: STEEL : BAR, PLATE, SHEET, STRIP, FORGINGS, AND EXTRUSIONS, 18 PERCENT NICKEL ALLOY, MARAGING, 200 KSI, 250 KSI, 300 KSI, AND 350 KSI, HIGH QUALITY, available from http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-S/MIL-S-46850D_19899/</ref> The higher grades have more cobalt and titanium in the alloy; the compositions below are taken from table 1 of MIL-S-46850D:
{| class="wikitable" style="text-align:center;"
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|0.05–0.15||0.05–0.15||0.05–0.15||0.05–0.15
|-
! scope="row"| Tensile strength,
|{{cvt|1379|MPa|ksi|abbr=values|sigfig=2}}||{{cvt|1724|MPa|ksi|abbr=values|sigfig=2}}||{{cvt|2068|MPa|ksi|abbr=values|sigfig=2}}||{{cvt|2413|MPa|ksi|abbr=values|sigfig=2}}
|}
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==Heat treatment cycle==
The steel is first [[annealing (metallurgy)|annealed]] at approximately {{convert|820|C|F}} for 15–30 minutes for thin sections and for 1 hour per {{cvt|25
Newer compositions of maraging steels have revealed other intermetallic stoichiometries and crystallographic relationships with the parent martensite, including rhombohedral and massive complex Ni<sub>50</sub>(X,Y,Z)<sub>50</sub> (Ni<sub>50</sub>M<sub>50</sub> in simplified notation).
==Processing of maraging steel==
The maraging steels are a popular class of structural materials because of their superior mechanical properties among different categories of steel. Their [[mechanical properties]] can be tailored for different applications using various processing techniques. Some of the most widely used processing techniques for manufacturing and tuning of mechanical behavior of maraging steels are listed as follows:
* '''Solution treatment''': As described in the section of Heat treatment cycle, the maraging steel is heated to a specific temperature range, after which it is quenched rapidly. In this step the alloying elements are dissolved, and a homogeneous [[microstructure]] is achieved. Homogeneous [[microstructure]] thus achieved improves the overall mechanical behavior of maraging steels such as fracture toughness and fatigue resistance.
* '''Aging of maraging steels''': It is an important processing step as this step leads to precipitation of [[intermetallic]] compounds such Ni<sub>3</sub>Al, Ni<sub>3</sub>Mo, Ni<sub>3</sub>Ti, etc. The semicoherent [[precipitates]] obtained during normal aging and incoherent precipitates obtained after [[overaging]] contribute to improvement of mechanical behavior by activating various strengthening mechanisms related to hindering of dislocation motion by precipitates. Strengthening mechanisms such as [[precipitate hardening]] where precipitates hinder dislocation motion via Orowan mechanism or dislocation bowing lead to increase in the ultimate tensile strength of maraging steels. Aging is also beneficial for reducing the microstructural heterogeneities which may occur due to non-uniform thermal distribution along the building direction in arc additive manufactured samples.<ref>{{citation|last1 = Xu | first1 = Xiangfang | last2 = Ganguly | first2 = Supriyo | last3 = Ding | first3 = Jialuo | last4 = Guo | first4 = Shun | last5 = Williams | first5 = Stewart |last6 = Martina | first6 = Filomeno | doi = 10.1016/j.matchar.2017.12.002 | title = Microstructural evolution and mechanical properties of maraging steel produced by wire + arc additive manufacture process | journal = Materials Characterization | volume = 143 | pages = 152–162 | year = 2018| hdl = 1826/12819 | s2cid = 115137237 | hdl-access = free }}</ref>
* '''Laser Powder Bed Fusion (LPBF)''': Laser Powder Bed Fusion is an [[additive manufacturing]] technique used to create components of intricate geometries using a powder metal which is fused together layer by layer using localized high power-density heat source such as a [[laser]]. The materials can be tailored to have specific mechanical properties by optimizing the process parameters associated with LPBF. It has been observed that processing parameters such as laser scanning speed, power and the scanning space can have significant effects on the mechanical properties of 300 maraging steel such as [[tensile strength]], [[microhardness]], and impact [[toughness]]. Along with the processing parameters, the type of heat treatment subjected to LPBF steels also play an important role. It is observed that processing parameters which have a higher magnitude reduce the relative density of the sample due to rapid vaporization or creation of voids and pores. It is also observed that the microhardness and strength of the steel decreases after solution treatment due to [[austenite]] reversion and disappearance of cellular microstructure. On the other hand, aging treatment after solution treatment increases the microhardness and tensile strength of steel which is attributed to formation of precipitates such as Ni<sub>3</sub>Mo, Ni<sub>3</sub>Ti, Fe<sub>2</sub>Mo. The impact toughness increases after solution treatment but decreases after aging treatment, which can be attributed to the underlying microstructure consisting of tiny precipitates acting as regions of stress concentrators for crack formation.<ref>{{citation|last1 = Bai | first1 = Yuchao | last2 = Yang | first2 = Yongqiang | last3 = Wang | first3 = Di | last4 = Zhang | first4 = Mingkang | doi = 10.1016/j.msea.2017.06.033 | title = Influence mechanism of parameters process and mechanical properties evolution mechanism of maraging steel 300 by selective laser melting | journal = Materials Science and Engineering: A | volume = 703 | pages = 116–123 | year = 2017}}</ref> Formation of nanoscale precipitates of [[intermetallic]] compounds after aging process lead to marked increase in yield and ultimate tensile strength but substantial reduction in ductility of the material. This change in macroscopic behavior of the material can be linked to the evolution of microstructure from dimple to quasi-cleavage fracture morphology.<ref>{{citation|last1 = Suryawanshi | first1 = Jyoti | last2 = Prashanth | first2 = K.G. | last3 = Ramamurty | first3 = U. | doi = 10.1016/j.jallcom.2017.07.177 | title = Tensile, fracture, and fatigue crack growth properties of a 3D printed maraging steel through selective laser melting | journal = Journal of Alloys and Compounds | volume = 725 | pages = 355–364 | year = 2017}}</ref> Aging followed by solution treatment of selective laser melted steels also reduces the amount of retained austenite in the [[martensitic]] matrix and lead to change in the grain orientation.<ref>{{citation|last1 = Mutua | first1 = James | last2 = Nakata | first2 = Shinya | last3 = Onda | first3 = Tetsuhiko | last4 = Chen | first4 = Zhong-Chun | doi = 10.1016/j.matdes.2017.11.042 | title = Optimization of selective laser melting parameters and influence of post heat treatment on microstructure and mechanical properties of maraging steel | journal = Materials & Design | volume = 139 | pages = 486–497 | year = 2018}}</ref> Aging can reduce the plastic anisotropy to some extent, but directionality of properties is largely influenced by its fabrication history.<ref>{{citation|last1 = Mooney | first1 = Barry | last2 = Kourousis | first2 = Kyriakos I | last3 = Raghavendra | first3 = Ramesh | doi = 10.1016/j.addma.2018.10.032 | title = Plastic anisotropy of additively manufactured maraging steel: Influence of the build orientation and heat treatments | journal = Additive Manufacturing | volume = 25 | pages = 19–31 | year = 2019| hdl = 10344/7510 | s2cid = 139243144 | hdl-access = free }}</ref>
* '''[[Severe plastic deformation]]''': It leads to increase in dislocation density in the materials which in turn assists in the ease of formation of intermetallic precipitates due to availability of faster diffusion pathways through the dislocation cores. It has been observed that plastic deformation before aging leads to reduced peak aging time and increase in peak hardness.<ref>{{citation|last1 = Tian | first1 = Jialong | last2 = Wang | first2 = Wei | last3 = Li | first3 = Huabing | last4 = Shahzad | first4 = M Babar |last5 = Shan | first5 = Yiyin | last6 = Jiang | first6 = Zhouhua |last7 = Yang | first7 = Ke | doi = 10.1016/j.matchar.2019.109827 | title = Effect of deformation on precipitation hardening behavior of a maraging steel in the aging process | journal = Materials Characterization | volume = 155 | pages = 109827 | year = 2019| s2cid = 199188852 }}</ref> Precipitate morphology in severely plastically deformed steel changes and becomes plate-like when overaged which is attributed to higher dislocation density. This in turn leads to significant reduction in ductility and increase in strength of the material. Along with morphology, the orientation of precipitates also play an important role in micromechanism of deformation as they induce [[anisotropy]] to the mechanical properties.<ref>{{citation|last1 = Jacob | first1 = Kevin | last2 = Roy | first2 = Abhinav | last3 = Gururajan | first3 = MP | last4 = Jaya | first4 = B Nagamani | doi = 10.1016/j.mtla.2022.101358 | title = Effect of dislocation network on precipitate morphology and deformation behaviour in maraging steels: modelling and experimental validation | journal = Materialia | volume = 21 | pages = 101358 | year = 2022| s2cid = 246668007 }}</ref>
==Uses==
Maraging steel's strength and malleability in the pre-aged stage allows it to be formed into thinner rocket and missile skins than other steels, reducing weight for a given strength.<ref>{{cite news|author=Joby Warrick |url=https://www.washingtonpost.com/world/national-security/nuclear-ruse-posing-as-toymaker-chinese-merchant-allegedly-sought-us-technology-for-iran/2012/08/11/f1c66d9a-e265-11e1-ae7f-d2a13e249eb2_story.html?wpisrc=nl_headlines |title=Nuclear ruse: Posing as toymaker, Chinese merchant allegedly sought U.S. technology for Iran |newspaper=The Washington Post |date=2012-08-11 |accessdate=2014-02-21}}</ref> Maraging steels have very stable properties and, even after overaging due to excessive temperature, only soften slightly. These alloys retain their properties at mildly elevated [[operating temperature]]s and have maximum service temperatures of over {{convert|400|°C|F|sigfig=2}}.{{Citation needed|date=August 2008}} They are suitable for engine components, such as crankshafts and gears, and the firing pins of automatic weapons that cycle from hot to cool repeatedly while under substantial load. Their uniform expansion and easy machinability before aging make maraging steel useful in high-wear components of [[assembly line]]s and [[die (manufacturing)|dies]]. Other ultra-high-strength steels, such as [[Aermet|AerMet]] alloys, are not as machinable because of their carbide content.
In the sport of [[fencing]], blades used in competitions run under the auspices of the [[Fédération Internationale d'Escrime]] are usually made with maraging steel. Maraging blades are superior for [[foil (sword)|foil]] and [[épée]] because crack propagation in maraging steel is 10 times slower than in carbon steel, resulting in less frequent breaking of the blade and fewer injuries.{{efn-lr|However, the notion that maraging steel blades break flat is a fencing [[urban legend]]. Testing has shown that the blade-breakage patterns in carbon steel and maraging steel are identical due to the similarity in the loading mode during bending. Additionally, a crack is likely to start at the same point and propagate along the same path (although much more slowly), as crack propagation in [[fatigue (material)|fatigue]] is a plastic phenomenon rather than microstructural.}}<ref name="Juvinall">{{cite book|title = Fundamentals of Machine Component Design |edition = Fourth |last1 = Juvinall |first1 = Robert C. |last2= Marshek |first2= Kurt M. |year = 2006 |publisher = John Wiley & Sons, Inc. |isbn = 978-0-471-66177-1 |page = 69}}</ref> Stainless maraging steel is used in [[bicycle]] frames (e.g. Reynolds 953
Maraging steel is used in oil and gas sector as downhole tools and components due to its high mechanical strength.<ref>{{cite web |url=https://powder.samaterials.com/the-impact-of-18nI300-am-maraging-steel-in-3d-printing.html |title=The Impact of 18NI300-AM Maraging Steel in 3D Printing |website=Stanford Advanced Materials |access-date=Aug 1, 2024}}</ref> The steel's resistance to [[hydrogen embrittlement]] is critical in downhole environments where exposure to [[hydrogen sulfide | hydrogen sulfide (H₂S)]] can lead to material degradation and failure.<ref>{{cite book |last1=Garrison |first1=W.M. |last2=Moody |first2=N.R |year=2012 |title=Gaseous Hydrogen Embrittlement of Materials in Energy Technologies |publisher=Woodhead Publishing |editor-last=Gangloff |editor-first=Richard |chapter=Chapter 12 - Hydrogen embrittlement of high strength steels |pages=421–492 |isbn=9781845696771}}</ref>
American musical instrument string producer [[Ernie Ball Inc.|Ernie Ball]] has made a specialist type of [[electric guitar]] [[Guitar string|string]] out of maraging steel, claiming that this alloy provides more output and enhanced tonal response.<ref>{{Cite web
|title=Slinky M-Steel Electric Guitar Strings
|website=Ernie Ball
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==Physical properties==
* [[Density]]: 8.1
* [[Specific heat]], mean for 0–100 °C (32–212 °F): 452
* [[Melting point]]:
* [[Thermal conductivity]]: 25.5
* Mean [[coefficient of thermal expansion]]: 11.3×10<sup>−6</sup> K<sup>−1</sup> (20.3×10<sup>−6</sup> °F<sup>−1</sup>)
* [[yield strength|Yield tensile strength]]: typically {{convert|1400|–|2400|MPa|
* Ultimate [[tensile strength]]: typically {{convert|1.6|–|2.5|GPa|
* Elongation at break: up to 15%
* K<sub>IC</sub> fracture toughness: up to 175
* [[Young's modulus]]: {{convert|210|GPa|
| last1 = Ohue | first1 = Yuji
| last2 = Matsumoto | first2 = Koji
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| date = 10 September 2007
}}</ref>
* [[Shear modulus]]: {{convert|77|GPa|
* [[Bulk modulus]]: {{convert|140|GPa|
* [[Hardness]] (aged): 50 HRC (grade 250); 54 HRC (grade 300); 58 HRC (grade 350)<ref>{{Cite web |title=Maraging 250 / VASCOMAX 250 Steel |url=https://www.ssa-corp.com/en/maraging-250-AMS-6512.php |website=Service Steel Aerospace|date=10 December 2019 }}</ref><ref>{{Cite web |title=Maraging 300 / VASCOMAX 300 Steel |url=https://www.ssa-corp.com/en/maraging-300-AMS-6514.php |website=Service Steel Aerospace|date=10 December 2019 }}</ref><ref>{{Cite web |title=Maraging 350 / VASCOMAX 350 Steel |url=https://www.ssa-corp.com/en/maraging-350-AMS-6515.php |website=Service Steel Aerospace|date=10 December 2019 }}</ref>
==See also==
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==External links==
*[http://www.matthey.ch/en/alloys/maraging-steels-durnico-durimphy-ultrafort-durinox-phynox Maraging steel data sheets] {{Webarchive|url=https://web.archive.org/web/20160815131638/http://www.matthey.ch/en/alloys/maraging-steels-durnico-durimphy-ultrafort-durinox-phynox |date=2016-08-15 }}
[[Category:Steels]]
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