Alloying effects on creep and oxidation resistance of austenitic stainless steel alloys employing intermetallic precipitates

Yamamoto, Yukinori; Takeyama, Masao; Lu, Z. P.; Liu, Chang; Evans, N. D.; Maziasz, P.J.; Brady, Michael P.

doi:10.1016/j.intermet.2007.12.005

Cited by 135 publications

(74 citation statements)

References 14 publications

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“…The shape of W-enriched Laves phases is also near spherical, which is more coherent and stable than needle-shaped precipitates. [13] In addition to the more stable feature of Laves phase in W-containing alloys, a high Laves phase volume fraction, which is beneficial in order to reach a high-precipitation-strengthening level, can be achieved by increasing the W level. As a consequence, several researchers now use Laves phase as the principal strengthening precipitate in the design of new creepresistant alloys.…”

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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“…16) Zhao et al 20) reported that Si could stabilized the Laves phase at lower temperatures and its Laves phase was expressed as (Cr, Si) 2 Nb in Cr-Nb-Si ternary system. Maziasz 21) and Yamamoto et al 22) reported that adding Si to the heat-resisting austenitic steel promotes the formation of the Fe 2 (Mo, Nb) Laves phase, but does not change the phase equilibrium between -Fe and Laves phase. In a study of a 9Cr-2Mo-Si steel, Iseda et al 11) reported that Si occupy the A site of the Mo-Laves phase, and the Laves phase could be expressed as (Fe, Cr, Si) 2 Mo according to the experimental results of analyzing the Laves phase using energy dispersive spectrometry (EDS).…”

Section: )mentioning

confidence: 99%

Effect of Si on Precipitation Behavior of Nb-Laves Phase and Amount of Nb in Solid Solution at Elevated Temperature in High Purity 17%Cr-0.5%Nb Steels

Kato¹,

Ito

Kato

et al. 2010

Mater. Trans.

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The effect of Si was investigated on the precipitation behavior and the amount of Nb in solid solution at temperature ranging from 1073 to 1173 K in high purity 17Cr-0.5Nb steels. Adding Si promoted the precipitation of the Nb Laves phase and then decreased the solubility of Nb in steels. The Nb Laves phase which was composed of Fe, Cr and Nb could be expressed as (Fe, Cr) 2 Nb in a 0.002 mass% Si steel. On the other hand, in a 0.5 mass% Si steel the Nb Laves phase which was composed of Fe, Si, Cr and Nb could be expressed as (Fe, Si, Cr) 2 Nb. Based on calculations from the experimental results assuming the Laves phase is Fe 2 Nb, the standard free energy change of the Fe 2 Nb precipitation reaction was about À61 k J/mol for a 0.002 mass% Si steel.

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“…Austenitic stainless steels have an FCC crystal structure which allows them to have good high-temperature creep resistance, which can be improved significantly with dispersions of MC carbides (M can be Nb, Ti, or V) [1][2][3][4][5][6][7]. They also have lower cost when compared with Ni-based superalloys.…”

Section: Introductionmentioning

confidence: 99%

“…Alumina is thermodynamically more stable and generally offers the potential for greater protection in many aggressive environments. The main problem with creating an aluminaforming austenitic (AFA) stainless steel is that aluminum is highly bcc stabilizing in iron [1][2][3][4][5][6][7]. These alloys also require significant quantities of chromium to help promote the formation of an alumina scale.…”

Section: Introductionmentioning

confidence: 99%

“…Oak Ridge National Laboratory (ORNL) has developed a class of AFA alloys for use in highly aggressive atmospheres [1][2][3][4][5][6][7]. The baseline alloys were a family of austenitic stainless steels called the high-temperature ultrafine-precipitationstrengthened steel (HTUPS) [15], which have typical compositions of (wt%) Fe14Cr-16Ni-2.5Mo-2Mn with additions of B, C, Nb, P, Ti, and V in order to balance mechanical properties and oxidation resistance as well as form nanoscale precipitates (such as Fe 2 Nb Laves phase, B2-NiAl, c 0 -Ni 3 Al, M 23 C 6 and MC) for strength at high temperatures.…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Water Vapor on the Oxidation Behavior of Alumina Forming Austenitic Stainless Steels

et al. 2015

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The isothermal oxidation behavior of three alumina forming austenitic (AFA) stainless steels with varying composition was studied at 650 and 800°C in dry air and gases which contained water vapor. The AFA alloys exhibited better oxidation resistance than a ''good chromia former'' at 650°C, particularly in H 2 Ocontaining atmospheres by virtue of alumina-scale formation. Although the AFA alloys were more resistant than chromia formers, their oxidation resistance was degraded at 650°C in the presence of water vapor. In dry air the AFA alloys formed, thin continuous alumina scales, whereas in Ar-4%H 2 -3%H 2 O the areas of continuous alumina were reduced and Fe oxide-rich nodules and regions of Cr, Mnrich oxides formed. In some regions internal oxidation of the aluminum occurred in the H 2 O-containing gas. The alloy OC8 had slightly better resistance than OC4 or OC5 in this atmosphere. The alumina-forming capability of the AFA alloys decreases with increasing temperature and, at 800°C, they are borderline alumina formers, even in dry air. The oxidation resistance of all three alloys was degraded at 800°C in atmospheres, which contained water vapor (Air-10%H 2 O, Ar-3%H 2 O and Ar-4%H 2 -3%H 2 O). The areas, which formed continuous alumina, were reduced in these atmospheres and areas of internal oxidation occurred. However, as a result of the borderline alumina-forming capability of the AFA alloys it was not possible to determine which of the H 2 O-containing atmospheres was more severe or to rank the alloys in terms of their performance. The experimental results indicate that the initial microstructure of the AFA alloys also plays a role in their oxidation performance. Less protective oxides formed at 800°C when alloy OC8 was equilibrated before exposure rather than being exposed in the as-processed condition.

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Alloying effects on creep and oxidation resistance of austenitic stainless steel alloys employing intermetallic precipitates

Cited by 135 publications

References 14 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 Si on Precipitation Behavior of Nb-Laves Phase and Amount of Nb in Solid Solution at Elevated Temperature in High Purity 17%Cr-0.5%Nb Steels

The Effects of Water Vapor on the Oxidation Behavior of Alumina Forming Austenitic Stainless Steels

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