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Maraging steel
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| Other iron-based materials |
Maraging steels (a portmanteau of "martensitic" and "aging") are steels that possess 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 from precipitation of intermetallic compounds rather than from carbon. The principal alloying metal is 15 to 25 wt% nickel.[1] Secondary alloying metals, which include cobalt, molybdenum and titanium, are added to produce intermetallic precipitates.[1]
The first maraging steel was developed by Clarence Gieger Bieber at Inco in the late 1950s. It produced 20 and 25 wt% Ni steels with small additions of aluminium, titanium, and niobium.[2] The intent was to induce age-hardening with the aforementioned intermetallics in an iron-nickel martensitic matrix, and it was discovered that Co and Mo complement each other very well. Commercial production started in December 1960.[3] A rise in the price of Co in the late 1970s led to cobalt-free maraging steels.[4]
The common, non-stainless grades contain 17–19 wt% Ni, 8–12 wt% Co, 3–5 wt% Mo and 0.2–1.6 wt% Ti.[5] Addition of chromium produces corrosion-resistant stainless grades. This also indirectly increases hardenability as they require less Ni; high-Cr, high-Ni steels are generally austenitic and unable to become martensite when heat treated, while lower-Ni steels can.
Alternative variants of Ni-reduced maraging steels are based on alloys of Fe and Mn plus minor additions of Al, Ni and Ti with compositions between Fe-9wt% Mn to Fe-15wt% Mn qualify used.[6] The manganese has an effect similar to 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.[7] The latter effect enables the design of maraging-transformation-induced-plasticity (TRIP) steels.[8]
- ^ a b 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
- ^ U.S. patent 3,093,518
- ^ https://nickelinstitute.org/en/library/technical-guides/18-nickel-maraging-steel-engineering-properties-4419/
- ^ Sha, W; Guo, Z (2009-10-26). Maraging Steels: Modelling of Microstructure, Properties and Applications. Elsevier.
- ^ INCO. "18% Nickel Maraging Steel – Engineering Properties". Nickel Institute.
- ^ 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.
- ^ 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
- ^ 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
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