Maraging steel

Last updated

Maraging steels (a portmanteau of "martensitic" and "aging") are steels 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 of intermetallic compounds. The principal alloying element is 15 to 25 wt% nickel. [1] Secondary alloying elements, which include cobalt, molybdenum and titanium, are added to produce intermetallic precipitates. [1] Original development (by Bieber of 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; a rise in the price of cobalt in the late 1970s led to the development of cobalt-free maraging steels. [2]

Contents

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 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. [3] 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. [4] The latter effect enables the design of maraging-TRIP steels where TRIP stands for Transformation-Induced-Plasticity. [5]

Properties

Due to the low carbon content (less than 0.03%) [6] maraging steels have good machinability. Prior to aging, they may also be cold rolled to as much as 90% without cracking. Maraging steels offer good weldability, but must be aged afterward to restore the original properties to the heat affected zone. [1]

When heat-treated the alloy has very little dimensional change, so it is often machined to its final dimensions. Due to the high alloy content maraging steels have a high hardenability. Since ductile FeNi martensites are formed upon cooling, cracks are non-existent or negligible. The steels can be nitrided to increase case hardness and polished to a fine surface finish.

Non-stainless varieties of maraging steel are moderately corrosion-resistant and resist stress corrosion and hydrogen embrittlement. Corrosion-resistance can be increased by cadmium plating or phosphating.

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 US military standard MIL-S-46850D. [7] The higher grades have more cobalt and titanium in the alloy; the compositions below are taken from table 1 of MIL-S-46850D:

Maraging steel compositions, by grade
ElementGrade 200Grade 250Grade 300Grade 350
Ironbalancebalancebalancebalance
Nickel17.0–19.017.0–19.018.0–19.018.0–19.0
Cobalt8.0–9.07.0–8.58.5–9.511.5–12.5
Molybdenum3.0–3.54.6–5.24.6–5.24.6–5.2
Titanium0.15–0.250.3–0.50.5–0.81.3–1.6
Aluminium0.05–0.150.05–0.150.05–0.150.05–0.15
Tensile strength, MPa (ksi)1,379 (200)1,724 (250)2,068 (300)2,413 (350)

That family is known as the 18Ni maraging steels, from its nickel percentage. There is also a family of cobalt-free maraging steels which are cheaper but not quite as strong; one example is Fe-18.9Ni-4.1Mo-1.9Ti. There has been Russian and Japanese research in Fe-Ni-Mn maraging alloys. [2]

Heat treatment cycle

The steel is first annealed at approximately 820 °C (1,510 °F) for 15–30 minutes for thin sections and for 1 hour per 25 mm (1 in) thickness for heavy sections, to ensure formation of a fully austenitized structure. This is followed by air cooling or quenching to room temperature to form a soft, heavily dislocated iron-nickel lath (untwinned) martensite. Subsequent aging (precipitation hardening) of the more common alloys for approximately 3 hours at a temperature of 480 to 500 °C (900 to 930 °F) produces a fine dispersion of Ni3(X,Y) intermetallic phases along dislocations left by martensitic transformation, where X and Y are solute elements added for such precipitation. Overaging leads to a reduction in stability of the primary, metastable, coherent precipitates, leading to their dissolution and replacement with semi-coherent Laves phases such as Fe2Ni/Fe2Mo. Further excessive heat-treatment brings about the decomposition of the martensite and reversion to austenite.

Newer compositions of maraging steels have revealed other intermetallic stoichiometries and crystallographic relationships with the parent martensite, including rhombohedral and massive complex Ni50(X,Y,Z)50 (Ni50M50 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:

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. [15] 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 temperatures and have maximum service temperatures of over 400 °C (750 °F).[ citation needed ] 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 lines and dies. Other ultra-high-strength steels, such as 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 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. [lower-roman 1] [16] Stainless maraging steel is used in bicycle frames (e.g. Reynolds 953 introduced in 2013) [17] and golf club heads. [18] It is also used in surgical components and hypodermic syringes, but is not suitable for scalpel blades because the lack of carbon prevents it from holding a good cutting edge.

American musical instrument string producer Ernie Ball has made a specialist type of electric guitar string out of maraging steel, claiming that this alloy provides more output and enhanced tonal response. [19]

The production, import, and export of maraging steels by certain entities, such as the United States, [20] is closely monitored by international authorities because it is particularly suited for use in gas centrifuges for uranium enrichment; [21] lack of maraging steel significantly hampers the uranium-enrichment process. Older centrifuges used aluminum tubes, while modern ones use carbon fiber composite.[ citation needed ]

Physical properties

See also

Related Research Articles

<span class="mw-page-title-main">Heat treating</span> Process of heating something to alter it

Heat treating is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve the desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, carburizing, normalizing and quenching. Although the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.

<span class="mw-page-title-main">Martensite</span> Type of steel crystalline structure

Martensite is a very hard form of steel crystalline structure. It is named after German metallurgist Adolf Martens. By analogy the term can also refer to any crystal structure that is formed by diffusionless transformation.

<span class="mw-page-title-main">Austenite</span> Metallic, non-magnetic allotrope of iron or a solid solution of iron, with an alloying element

Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures. The austenite allotrope is named after Sir William Chandler Roberts-Austen (1843–1902); it exists at room temperature in some stainless steels due to the presence of nickel stabilizing the austenite at lower temperatures.

<span class="mw-page-title-main">Bainite</span>

Bainite is a plate-like microstructure that forms in steels at temperatures of 125–550 °C. First described by E. S. Davenport and Edgar Bain, it is one of the products that may form when austenite is cooled past a temperature where it is no longer thermodynamically stable with respect to ferrite, cementite, or ferrite and cementite. Davenport and Bain originally described the microstructure as being similar in appearance to tempered martensite.

<span class="mw-page-title-main">High-strength low-alloy steel</span> Type of alloy steel

High-strength low-alloy steel (HSLA) is a type of alloy steel that provides better mechanical properties or greater resistance to corrosion than carbon steel. HSLA steels vary from other steels in that they are not made to meet a specific chemical composition but rather specific mechanical properties. They have a carbon content between 0.05 and 0.25% to retain formability and weldability. Other alloying elements include up to 2.0% manganese and small quantities of copper, nickel, niobium, nitrogen, vanadium, chromium, molybdenum, titanium, calcium, rare-earth elements, or zirconium. Copper, titanium, vanadium, and niobium are added for strengthening purposes. These elements are intended to alter the microstructure of carbon steels, which is usually a ferrite-pearlite aggregate, to produce a very fine dispersion of alloy carbides in an almost pure ferrite matrix. This eliminates the toughness-reducing effect of a pearlitic volume fraction yet maintains and increases the material's strength by refining the grain size, which in the case of ferrite increases yield strength by 50% for every halving of the mean grain diameter. Precipitation strengthening plays a minor role, too. Their yield strengths can be anywhere between 250–590 megapascals (36,000–86,000 psi). Because of their higher strength and toughness HSLA steels usually require 25 to 30% more power to form, as compared to carbon steels.

<span class="mw-page-title-main">Martensitic stainless steel</span> One of the 5 crystalline structures of stainless steel

Martensitic stainless steel is a type of stainless steel alloy that has a martensite crystal structure. It can be hardened and tempered through aging and heat treatment. The other main types of stainless steel are austenitic, ferritic, duplex, and precipitation hardened.

<span class="mw-page-title-main">Carbon steel</span> Steel in which the main interstitial alloying constituent is carbon

Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:

In metallurgy, a shape-memory alloy (SMA) is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated. It is also known in other names such as memory metal, memory alloy, smart metal, smart alloy, and muscle wire. The "memorized geometry" can be modified by fixating the desired geometry and subjecting it to a thermal treatment, for example a wire can be taught to memorize the shape of a coil spring.

<span class="mw-page-title-main">Inconel</span> Austenitic nickel-chromium superalloys

Inconel is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or mechanical loads. Inconel alloys are oxidation- and corrosion-resistant, when heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high-temperature applications where aluminum and steel would succumb to creep as a result of thermally-induced crystal vacancies. Inconel's high-temperature strength is developed by solid solution strengthening or precipitation hardening, depending on the alloy.

<span class="mw-page-title-main">Tempering (metallurgy)</span> Process of heat treating used to increase the toughness of iron-based alloys

Tempering is a process of heat treating, which is used to increase the toughness of iron-based alloys. Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air. The exact temperature determines the amount of hardness removed, and depends on both the specific composition of the alloy and on the desired properties in the finished product. For instance, very hard tools are often tempered at low temperatures, while springs are tempered at much higher temperatures.

Cryogenic hardening is a cryogenic treatment process where the material is cooled to approximately −185 °C (−301 °F), usually using liquid nitrogen. It can have a profound effect on the mechanical properties of certain steels, provided their composition and prior heat treatment are such that they retain some austenite at room temperature. It is designed to increase the amount of martensite in the steel's crystal structure, increasing its strength and hardness, sometimes at the cost of toughness. Presently this treatment is being used on tool steels, high-carbon, high-chromium steels and in some cases to cemented carbide to obtain excellent wear resistance. Recent research shows that there is precipitation of fine carbides in the matrix during this treatment which imparts very high wear resistance to the steels.

<span class="mw-page-title-main">Superalloy</span> Alloy with higher durability than normal metals

A superalloy, or high-performance alloy, is an alloy with the ability to operate at a high fraction of its melting point. Key characteristics of a superalloy include mechanical strength, thermal creep deformation resistance, surface stability, and corrosion and oxidation resistance.

In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling.

<span class="mw-page-title-main">Nickel titanium</span> High-durability alloy

Nickel titanium, also known as nitinol, is a metal alloy of nickel and titanium, where the two elements are present in roughly equal atomic percentages. Different alloys are named according to the weight percentage of nickel; e.g., nitinol 55 and nitinol 60.

Nickel aluminide typically refers to the one of the two most widely used compounds, Ni3Al or NiAl, but can refer to most aluminides from the Ni-Al system. These alloys are widely used due to their corrosion resistance, low-density and easy production. Ni3Al is of specific interest as the strengthening γ' phase precipitate in nickel-based superalloys allowing for high temperature strength up to 0.7-0.8 of its melting temperature. Meanwhile, NiAl displays excellent properties such as low-density (lower than that of Ni3Al), good thermal conductivity, oxidation resistance and high melting temperature. These properties, make it ideal for special high temperature applications like coatings on blades in gas turbines and jet engines. However, both these alloys do have the disadvantage of being quite brittle at room temperature while Ni3Al remains brittle at high temperatures as well. Although, it has been shown that Ni3Al can be made ductile when manufactured as a single crystal as opposed to polycrystalline. Another application was demonstrated in 2005, when the most abrasion-resistant material was reportedly created by embedding diamonds in a matrix of nickel aluminide.

AerMet alloy is an ultra-high strength type of martensitic alloy steel. The main alloying elements are cobalt and nickel, but chromium, molybdenum and carbon are also added. Its exceptional properties are hardness, tensile strength, fracture toughness and ductility. Aermet is weldable with no preheating needed. AerMet alloy is not corrosion resistant, so it must be sealed if used in a moist environment. AerMet is a registered trademark of Carpenter Technology Corporation.

Methods have been devised to modify the yield strength, ductility, and toughness of both crystalline and amorphous materials. These strengthening mechanisms give engineers the ability to tailor the mechanical properties of materials to suit a variety of different applications. For example, the favorable properties of steel result from interstitial incorporation of carbon into the iron lattice. Brass, a binary alloy of copper and zinc, has superior mechanical properties compared to its constituent metals due to solution strengthening. Work hardening has also been used for centuries by blacksmiths to introduce dislocations into materials, increasing their yield strengths.

<span class="mw-page-title-main">Austempering</span>

Austempering is heat treatment that is applied to ferrous metals, most notably steel and ductile iron. In steel it produces a bainite microstructure whereas in cast irons it produces a structure of acicular ferrite and high carbon, stabilized austenite known as ausferrite. It is primarily used to improve mechanical properties or reduce / eliminate distortion. Austempering is defined by both the process and the resultant microstructure. Typical austempering process parameters applied to an unsuitable material will not result in the formation of bainite or ausferrite and thus the final product will not be called austempered. Both microstructures may also be produced via other methods. For example, they may be produced as-cast or air cooled with the proper alloy content. These materials are also not referred to as austempered.

Twinning-Induced Plasticity steel which is also known as TWIP steel is a class of austenitic steels which can deform by both glide of individual dislocations and mechanical twinning on the {1 1 1}γ<1 1 >γ system. They have outstanding mechanical properties at room temperature combining high strength and ductility based on a high work-hardening capacity. TWIP steels have mostly high content in Mn and small additions of elements such C, Si, or Al. The steels have low stacking fault energy at room temperature. Although the details of the mechanisms controlling strain-hardening in TWIP steels are still unclear, the high strain-hardening is commonly attributed to the reduction of the dislocation mean free path with the increasing fraction of deformation twins as these are considered to be strong obstacles to dislocation glide. Therefore, a quantitative study of deformation twinning in TWIP steels is critical to understand their strain-hardening mechanisms and mechanical properties. Deformation twinning can be considered as a nucleation and growth process. Twin growth is assumed to proceed by co-operative movement of Shockley partials on subsequent {111} planes.

<span class="mw-page-title-main">HY-80</span> Alloy steel

HY-80 is a high-tensile, high yield strength, low alloy steel. It was developed for use in naval applications, specifically the development of pressure hulls for the US nuclear submarine program and is still currently used in many naval applications. It is valued for its strength to weight ratio.

References

  1. 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 is a plastic phenomenon rather than microstructural.
  1. 1 2 3 Degarmo, E. Paul; Black, J. T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, p. 119, ISBN   0-471-65653-4
  2. 1 2 Sha, W; Guo, Z (2009-10-26). Maraging Steels: Modelling of Microstructure, Properties and Applications. Elsevier.
  3. Raabe, D.; Sandlöbes, S.; Millan, J. J.; Ponge, D.; Assadi, H.; Herbig, M.; Choi, P.P. (2013), "Segregation engineering enables nanoscale martensite to austenite phase transformation at grain boundaries: A pathway to ductile martensite", Acta Materialia, 61 (16): 6132–6152, Bibcode:2013AcMat..61.6132R, doi:10.1016/j.actamat.2013.06.055 .
  4. Dmitrieva, O.; Ponge, D.; Inden, G.; Millan, J.; Choi, P.; Sietsma, J.; Raabe, D. (2011), "Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation", Acta Materialia, 59 (1): 364–374, arXiv: 1402.0232 , Bibcode:2011AcMat..59..364D, doi:10.1016/j.actamat.2010.09.042, ISSN   1359-6454, S2CID   13781776
  5. Raabe, D.; Ponge, D.; Dmitrieva, O.; Sander, B. (2009), "Nano-precipitate hardened 1.5 GPa steels with unexpected high ductility", Scripta Materialia, 60 (12): 1141, doi:10.1016/j.scriptamat.2009.02.062
  6. Adrian P Mouritz, Introduction to Aerospace Materials, p. 244, Elsevier, 2012 ISBN   0857095153.
  7. 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/
  8. Xu, Xiangfang; Ganguly, Supriyo; Ding, Jialuo; Guo, Shun; Williams, Stewart; Martina, Filomeno (2018), "Microstructural evolution and mechanical properties of maraging steel produced by wire + arc additive manufacture process", Materials Characterization, 143: 152–162, doi:10.1016/j.matchar.2017.12.002, hdl: 1826/12819 , S2CID   115137237
  9. Bai, Yuchao; Yang, Yongqiang; Wang, Di; Zhang, Mingkang (2017), "Influence mechanism of parameters process and mechanical properties evolution mechanism of maraging steel 300 by selective laser melting", Materials Science and Engineering: A, 703: 116–123, doi:10.1016/j.msea.2017.06.033
  10. Suryawanshi, Jyoti; Prashanth, K.G.; Ramamurty, U. (2017), "Tensile, fracture, and fatigue crack growth properties of a 3D printed maraging steel through selective laser melting", Journal of Alloys and Compounds, 725: 355–364, doi:10.1016/j.jallcom.2017.07.177
  11. Mutua, James; Nakata, Shinya; Onda, Tetsuhiko; Chen, Zhong-Chun (2018), "Optimization of selective laser melting parameters and influence of post heat treatment on microstructure and mechanical properties of maraging steel", Materials & Design, 139: 486–497, doi:10.1016/j.matdes.2017.11.042
  12. Mooney, Barry; Kourousis, Kyriakos I; Raghavendra, Ramesh (2019), "Plastic anisotropy of additively manufactured maraging steel: Influence of the build orientation and heat treatments", Additive Manufacturing, 25: 19–31, doi:10.1016/j.addma.2018.10.032, hdl: 10344/7510 , S2CID   139243144
  13. Tian, Jialong; Wang, Wei; Li, Huabing; Shahzad, M Babar; Shan, Yiyin; Jiang, Zhouhua; Yang, Ke (2019), "Effect of deformation on precipitation hardening behavior of a maraging steel in the aging process", Materials Characterization, 155: 109827, doi:10.1016/j.matchar.2019.109827, S2CID   199188852
  14. Jacob, Kevin; Roy, Abhinav; Gururajan, MP; Jaya, B Nagamani (2022), "Effect of dislocation network on precipitate morphology and deformation behaviour in maraging steels: modelling and experimental validation", Materialia, 21: 101358, doi:10.1016/j.mtla.2022.101358, S2CID   246668007
  15. Joby Warrick (2012-08-11). "Nuclear ruse: Posing as toymaker, Chinese merchant allegedly sought U.S. technology for Iran". The Washington Post. Retrieved 2014-02-21.
  16. Juvinall, Robert C.; Marshek, Kurt M. (2006). Fundamentals of Machine Component Design (Fourth ed.). John Wiley & Sons, Inc. p. 69. ISBN   978-0-471-66177-1.
  17. "Reynolds turns 120: The history of Reynolds Technology". www.reynoldstechnology.biz. 20 December 2018. Retrieved 2022-12-29.
  18. "Maraging Steel in Golf Clubs". Golf Compendium. Retrieved 2022-12-29.
  19. "Slinky M-Steel Electric Guitar Strings". Ernie Ball. Retrieved 2020-07-15. Ernie Ball M-Steel Electric Guitar Strings are made of a patented Super Cobalt alloy wrapped around a Maraging steel hex core wire, producing a richer and fuller tone with a powerful low-end response.
  20. Consolidated Federal Regulations part 110--export and import of nuclear equipment and material , retrieved 2009-11-11.
  21. Patrikarakos, David (November 2012). Nuclear Iran: The Birth of an Atomic State. I.B. Tauris. p. 168. ISBN   978-1-78076-125-1.
  22. "Maraging Steels". imoa.info. International Molybdenum Association. Retrieved 8 April 2015.
  23. Ohue, Yuji; Matsumoto, Koji (10 September 2007). "Sliding–rolling contact fatigue and wear of maraging steel roller with ion-nitriding and fine particle shot-peening". Wear. 263 (1–6): 782–789. doi:10.1016/j.wear.2007.01.055.
  24. "Maraging 250 / VASCOMAX 250 Steel". Service Steel Aerospace. 10 December 2019.
  25. "Maraging 300 / VASCOMAX 300 Steel". Service Steel Aerospace. 10 December 2019.
  26. "Maraging 350 / VASCOMAX 350 Steel". Service Steel Aerospace. 10 December 2019.