A SANS and APT study of precipitate evolution and strengthening in a maraging steel

Simm, Thomas H.; Sun, Lin Zhu; Galvin, D.R.; Gilbert, Elliot P.; Venero, Diego Alba; Li, Y.; Martin, T.; Bagot, Paul A.J.; Moody, Michael P.; Hill, P.; Bhadeshia, H. K. D. H.; Birosca, S.; Rawson, M.; Perkins, Karen

doi:10.1016/j.msea.2017.07.013

Cited by 32 publications

(28 citation statements)

References 38 publications

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“…In order to provide a material solution for low pressure turbine shaft applications in jet engines, a novel maraging steel with ultra-high strength and good resistance to creep at temperatures up to 500 °C has recently been developed [8,9]. Unlike the traditional 18Ni maraging steels that mainly utilise Ni3Ti precipitates to provide strengthening, the new alloy contains much lower amount of Ni (around 7 wt.%).…”

Section: Introductionmentioning

confidence: 99%

A novel ultra-high strength maraging steel with balanced ductility and creep resistance achieved by nanoscale β-NiAl and Laves phase precipitates

et al. 2018

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A novel ultra-high strength precipitation hardened martensitic steel with balanced ductility and creep resistance has been developed. It utilises a unique combination of nanometre scale intermetallic precipitates of Laves phases and β-NiAl to achieve such properties. The mechanical properties of this steel were assessed by tensile and creep testing. With different heat treatments, this steel showed a remarkable combination of mechanical properties: yield strength of >1800 MPa, ultimate tensile strength of ~ 2000 MPa, tensile ductility up to ~8% at room temperature and creep rupture life > 2,000 hours under 700 MPa stress at 500 °C. The microstructures at different length scales were characterised using scanning / transmission electron microscopy and atom probe tomography. The austenisation and ageing temperatures were found be the key factors determining the microstructural development and resulting mechanical properties. Large primary Laves phase precipitates formed at lower austenisation temperatures resulted in reduced creep strength; whilst the small difference (20 °C) in ageing temperatures had significant impact on the spatial distribution characteristics of β-NiAl precipitates. Lower ageing temperature produced much smaller but more uniformly distributed β-NiAl precipitates which contributed to the higher observed yield strength. It is clear from this study that whilst this novel alloy system showed great potentials, careful design of heat treatment is still required to achieve balanced mechanical properties to meet the service requirements in aerospace propulsion systems.

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Section: Introductionmentioning

confidence: 99%

A novel ultra-high strength maraging steel with balanced ductility and creep resistance achieved by nanoscale β-NiAl and Laves phase precipitates

et al. 2018

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“…The contribution to creep behaviour is more complex; the resistance to creep can increase via strengthening by precipitation strengthening [ 1 , 7 ], but the resulting loss of solute can reduce the solid solution strengthening component, particularly during extended service at elevated temperatures [ 2 , 3 , 4 ]. In alloys similar to the one studied here [ 8 , 9 ], Laves phase had a tendency to form on boundaries and can range in size between around 10 nm and several 100 nm.…”

Section: Introductionmentioning

confidence: 67%

“…The background and matrix scattering was modelled using a Guinier Porod function; the Laves and NiAl phases were separated based on their size, since it is expected that NiAl will be smaller at all stages. More details of the SANS experimental set-up and analysis procedure can be found in the appendix and in a separate work [ 9 ]. Laves phase is separated into two types: (1) austenitisation Laves, formed during austenitisation; and (2) ageing Laves, formed during lower temperature ageing in the martensite region.…”

Section: Methodsmentioning

confidence: 99%

“…In previous work on this alloy, the influence of martensitic microstructure have been studied [ 19 ], and the phases and precipitation in the alloy have been studied by transmission electron microscopy (TEM) and atom probe tomography (APT) [ 8 ]. In a previous work a model [ 9 ] was presented to relate the precipitate volume fraction and size from small angle neutron scattering (SANS) measurements with the strength of three similar alloys one of which (F1E) is the one studied in this work. The components of strengthening were separated into: (a) precipitation strengthening due to Laves (Δ σ L ) and NiAl (Δ σ β ); (b) solid solution strengthening (Δ σ SS ); and (c) strengthening (Δ σ mart ) due to the structure the lath martensite and the intrinsic strength of iron (which can be considered as the stress needed to move a dislocation in a perfect BCC crystal structure, i.e., with no grain boundary or solid solution strengthening).…”

Section: Introductionmentioning

confidence: 99%

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The Effect of a Two-Stage Heat-Treatment on the Microstructural and Mechanical Properties of a Maraging Steel

et al. 2017

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Maraging steels gain many of their beneficial properties from heat treatments which induce the precipitation of intermetallic compounds. We consider here a two-stage heat-treatment, first involving austenitisation, followed by quenching to produce martensite and then an ageing treatment at a lower temperature to precipitation harden the martensite of a maraging steel. It is shown that with a suitable choice of the initial austenitisation temperature, the steel can be heat treated to produce enhanced toughness, strength and creep resistance. A combination of small angle neutron scattering, scanning electron microscopy, electron back-scattered diffraction, and atom probe tomography were used to relate the microstructural changes to mechanical properties. It is shown that such a combination of characterisation methods is necessary to quantify this complex alloy, and relate these microstructural changes to mechanical properties. It is concluded that a higher austenitisation temperature leads to a greater volume fraction of smaller Laves phase precipitates formed during ageing, which increase the strength and creep resistance but reduces toughness.

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“…The dominant strengthening factor is precipitate hardening by the intermetallic compounds [81], for example, fine Laves phase and β-NiAl in the novel maraging steel studied here [82][83][84][85]. Apart from precipitation, strong elements such as nickel have meltable sites, for example in enhancing hardenability.…”

Section: Strengthening Mechanismsmentioning

confidence: 97%

Creep-resistant aeroengine shaft steels: Precipitates and consequences

Huang

2019

Materials Science and Technology

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Creep resistant steels must be stable over long periods of time under severe operating conditions. This paper reviews precipitation in Cr-Mo steels and maraging steels destined for elevated temperature applications. It also covers aspects of structural evolution, strengthening and degradation, all of which are essential for alloy design. Two classes of steels are emphasised, those with origins in the power generation industries, and a novel approach based on intermetallic precipitates.

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A SANS and APT study of precipitate evolution and strengthening in a maraging steel

Cited by 32 publications

References 38 publications

A novel ultra-high strength maraging steel with balanced ductility and creep resistance achieved by nanoscale β-NiAl and Laves phase precipitates

A novel ultra-high strength maraging steel with balanced ductility and creep resistance achieved by nanoscale β-NiAl and Laves phase precipitates

The Effect of a Two-Stage Heat-Treatment on the Microstructural and Mechanical Properties of a Maraging Steel

Creep-resistant aeroengine shaft steels: Precipitates and consequences

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