Effect of nickel and cobalt addition on the precipitation-strength of 15Cr ferritic steels

Shibuya, Masachika; Toda, Yoshiaki; Sawada, Kota; Kushima, Hideaki; Kimura, Kazuhiro

doi:10.1016/j.msea.2011.03.088

Cited by 46 publications

(22 citation statements)

References 11 publications

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“…Generally, M 23 C 6 precipitates are located at lath boundaries and have a positive effect by pinning the lath boundaries during creep, [29] while the W-enriched Laves phase can be found both in the grain interior and boundaries [12,14,30] and restricts the movement of dislocations. Both effects decrease the creep rate, especially if the coarsening rates of both types of precipitates can be kept at a low value during the service.…”

Section: Combining M 23 C 6 and Laves Phase In One Alloymentioning

confidence: 99%

The Computational Design of W and Co-Containing Creep-Resistant Steels with Barely Coarsening Laves Phase and M23C6 as the Strengthening Precipitates

Zwaag

2014

Metall Mater Trans A

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Generally, Laves phase and M 23 C 6 are regarded as undesirable phases in creep-resistant steels due to their very high-coarsening rates and the resulting depletion of beneficial alloying elements from the matrix. In this study, a computational alloy design approach is presented to develop martensitic steels strengthened by Laves phase and/or M 23 C 6 , for which the coarsening rates are tailored such that they are at least one order of magnitude lower than those in existing alloys. Their volume fractions are optimized by tuning the chemical composition in parallel. The composition domain covering 10 alloying elements at realistic levels is searched by a genetic algorithm to explore the full potential of simultaneous maximization of the volume fraction and minimization of the precipitates coarsening rate. The calculations show that Co and W can drastically reduce the coarsening rate of Laves and M 23 C 6 and yield high-volume fractions of precipitates. Mo on the other hand was shown to have a minimal effect on coarsening. The strengthening effects of Laves phase and M 23 C 6 in the newly designed alloys are compared to existing counterparts, showing substantially higher precipitation-strengthening contributions especially after a long service time. New alloys were designed in which both Laves phase and M 23 C 6 precipitates act as strengthening precipitates. Successfully combining MX and M 23 C 6 was found to be impossible.

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Section: Combining M 23 C 6 and Laves Phase In One Alloymentioning

confidence: 99%

The Computational Design of W and Co-Containing Creep-Resistant Steels with Barely Coarsening Laves Phase and M23C6 as the Strengthening Precipitates

Zwaag

2014

Metall Mater Trans A

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“…15Cr1Mo steel gave ferritic and martensitic phases upon quenching, with volume fraction of martensite increasing with Ni addition. The precipitates observed were reported to be Laves phase and -phase (which are intermetallic compounds), Cr 23 C 6 (chromium carbide), and Z-phase (Cr(V, Nb)N) [8,31]. Ni was seen to cause preferential precipitation of Cr 23 C 6 at grain boundaries between the ferrite and martensite.…”

Section: Nickel (Ni)mentioning

confidence: 94%

“…In other words, cobalt-containing steels have a very low scrap value. In recent study, additions of Co and Ni were observed to strongly influence the creep strength and precipitation behaviour of intermetallic compounds (Laves phase, -phase, and -phase) during creep exposure at high temperature for 15Cr1Mo6W steel [31]. They found that creep strength is increased by precipitation of fine particles and homogenous dispersion of intermetallic particles in the ferritic matrix.…”

Section: Cobalt (Co)mentioning

confidence: 99%

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Physical Metallurgy of Modern Creep-Resistant Steel for Steam Power Plants: Microstructure and Phase Transformations

Igwemezie

Ugwuegbu

Mark

2016

Journal of Metallurgy

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The fact that the microstructure of steel depends on its composition and the heat treatment given to it has been heavily exploited in the design of steel for power plant applications. To obtain a steel that can function at the higher temperature where power plants operate without failure for extended life, heat treatment is needed to produce fine and highly stable dispersion of carbides, nitrides, and intermetallic compounds in the microstructure of the material. A significant contribution also comes from solid solution strengthening by substitutional solutes. We review here various types of phases, microstructures, functions, and interacting effects of the various alloying elements in the design of steel for modern power plant application.

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“…Kimura and Toda et al recently developed a super strong 15Cr ferritic creep resistant steel (hereafter referred as alloy 15Cr) through the PH of Laves phase (Fe 2 W) [4,[7][8][9][10][11][12][13], which remains stable over long term service at temperature up to 700°C. Moreover, the time dependence of the strengthening via Laves phase can be further improved through the modification of alloying elements, such as Co and W [14] so as to increase volume fraction and decrease the coarsening rate.…”

Section: Introductionmentioning

confidence: 99%

The impact of intended service temperature on the optimal composition of Laves and M23C6 precipitate strengthened ferritic creep resistant steels

Toda

Harada

et al. 2015

Computational Materials Science

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Effect of nickel and cobalt addition on the precipitation-strength of 15Cr ferritic steels

Cited by 46 publications

References 11 publications

The Computational Design of W and Co-Containing Creep-Resistant Steels with Barely Coarsening Laves Phase and M23C6 as the Strengthening Precipitates

The Computational Design of W and Co-Containing Creep-Resistant Steels with Barely Coarsening Laves Phase and M23C6 as the Strengthening Precipitates

Physical Metallurgy of Modern Creep-Resistant Steel for Steam Power Plants: Microstructure and Phase Transformations

The impact of intended service temperature on the optimal composition of Laves and M23C6 precipitate strengthened ferritic creep resistant steels

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