Effect of Co on Creep Behavior of a P911 Steel

Kipelova, Alla; Odnobokova, Marina; Belyakov, Andrey; Kaibyshev, Rustam

doi:10.1007/s11661-012-1390-3

Cited by 47 publications

(40 citation statements)

References 17 publications

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“…An alternative approach is to tailor the characteristics of such potentially detrimental phases by adding some other alloying elements in order to slow down the coarsening. In the literature, it has been reported that the coarsening rate of M 23 C 6 can be decreased moderately by adding B, Co, or W. [6][7][8][9][10] Abe [11,12] reported that the coarsening rate of Laves phase can also be effectively reduced by substituting W for Mo. The shape of W-enriched Laves phases is also near spherical, which is more coherent and stable than needle-shaped precipitates.…”

Section: Introductionmentioning

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: Introductionmentioning

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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“…Despite this fact, the creep strength of the 9Cr3W steel approaches to the level of the 9Cr2W steel with increasing rupture time up to 10 5 h according to estimation by Larson-Miller parameter. It is worth noting that effect of Co on the microstructural evolution under creep is nearly the same [18]. However, both Co and W additions could not prevent the breakdown of creep strength taking place at a rupture time of~2000 h for the P92 steel and the 9Cr2W steel, and at a rupture time of~10,000 for the 9Cr3W steel (Figure 3a,c).…”

Section: Contribution Of W To the Solid Solution Strengtheningmentioning

confidence: 92%

“…The enhanced long-term creep strength could be achieved by hindering this microstructural evolution. An effective way to achieve this goal is to slow down the diffusion-controlled processes, such as the climb of dislocations, knitting reaction between dislocation and lath boundaries, particle coarsening, etc., by such substitutional additives as Co, W, and Mo [1,9,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…It was recently shown that cobalt addition significantly hinders the coarsening of M 23 C 6 carbides and MX carbonitrides under creep conditions, which results in the superior creep resistance of martensitic steels [9,13,18,20]. This positive effect of Co is attributed to hindering diffusion within ferrite [9,18].…”

Section: Introductionmentioning

confidence: 99%

“…This positive effect of Co is attributed to hindering diffusion within ferrite [9,18]. Efficiency of W as an alloying element in hindering diffusion is much higher than that of Co. As a result, W and Mo are known as effective alloying additives to enhance creep resistance of high chromium martensitic steels [1,19].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Tungsten on Creep Behavior of 9%Cr–3%Co Martensitic Steels

Fedoseeva

Dudova

Kaibyshev

et al. 2017

Metals

Self Cite

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Abstract:The effect of increasing tungsten content from 2 to 3 wt % on the creep rupture strength of a 3 wt % Co-modified P92-type steel was studied. Creep tests were carried out at a temperature of 650 • C under applied stresses ranging from 100 to 220 MPa with a step of 20 MPa. It was found that an increase in W content from 2 to 3 wt % resulted in a +15% and +14% increase in the creep rupture strength in the short-term region (up to 10 3 h) and long-term one (up to 10 4 h), respectively. On the other hand, in the long-term creep region, the effect of W on creep strength diminished with increasing rupture time, up to complete disappearance at 10 5 h, because of depletion of excess W from the solid solution in the form of precipitation of the Laves phase particles. An increase in W content led to the increased amount of Laves phase and rapid coarsening of these particles under long-term creep. The contribution of W to the enhancement of creep resistance has short-term character.

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On the Cobalt − Tungsten/Chromium Balance in Martensitic Creep Resistant Steels

Zwaag

2017

steel research int.

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Recently, novel martensitic creep resistant steels strengthened by slowly coarsening Laves phase or stable M 23 C 6 precipitates have been identified both computationally and experimentally. The coarsening kinetics of these precipitates, traditionally considered to be very detrimental in creep steels, can be suppressed to a degree which makes them attractive strengthening factors by alloying such steels to high Cobalt levels. As high Co levels are undesirable for various reasons, in the present work, the characteristics of Laves phase and M 23 C 6 , in particular the volume fraction, coarsening rate, and precipitation strengthening factor, in newly designed alloys are computationally compared with those of existing Co-containing creep steels. The binary analyses of Co-M balance show that the Co-W levels are highly coupled for creep steels strengthened by Laves phase deposits and W can be used to partially replace Co to yield the same precipitation strengthening. For the M 23 C 6 strengthened alloys, irrespective of the Cr level, a high Co concentration is predicted to be necessary for a high creep resistance.

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Effect of Co on Creep Behavior of a P911 Steel

Cited by 47 publications

References 17 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

Effect of Tungsten on Creep Behavior of 9%Cr–3%Co Martensitic Steels

On the Cobalt − Tungsten/Chromium Balance in Martensitic Creep Resistant Steels

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