Advances in Physical Metallurgy and Processing of Steels. History of Power Plants and Progress in Heat Resistant Steels.

Masuyama, Fujimitsu

doi:10.2355/isijinternational.41.612

Cited by 478 publications

(177 citation statements)

References 6 publications

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“…Martensite is chosen as the (initial) microstructure of the matrix because of its good creep strength and its high resistance to thermal and creep fatigue during service in power plants. [18] Thus, the target microstructure is (1) a fully martensitic matrix, (2) a high-volume fraction of Laves phase or M 23 C 6 with a tuned lowcoarsening rate throughout its intended life time, and (3) a limited volume fraction of undesirable phases. In order to achieve the microstructural features listed above, a computational alloy design model involving a Genetic Algorithm (GA) optimization routine has been developed.…”

Section: Model Descriptionsmentioning

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: Model Descriptionsmentioning

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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“…For example, Mn alloy additions generally reduce high temperature creep strength in 9-12% Cr ferritic alloys. 31 The adherence of perovskite coatings is not established, and would need to be evaluated.…”

Section: Mitigationmentioning

confidence: 99%

Calculation of Reactive-evaporation Rates of Chromia

Holcomb

2008

Oxid Met

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A methodology is developed to calculate Cr evaporation rates from Cr 2 O 3 with a flat planar geometry. Variables include temperature, total pressure, gas velocity, and gas composition. The methodology was applied to solid oxide fuel cell conditions for metallic interconnects and to advanced steam turbines conditions. The high velocities and pressures of the advanced steam turbine led to evaporation predictions as high as 5.18 × 10 -8 kg/m 2 /s of CrO 2 (OH) 2 (g) at 760°C and 34.5 MPa. This is equivalent to 0.080 mm per year of solid Cr loss. Chromium evaporation is expected to be an important oxidation mechanism with the types of nickel-base alloys proposed for use above 650°C in advanced steam boilers and turbines. It is shown that laboratory experiments, with much lower steam velocities and usually much lower total pressure than found in advanced steam turbines, would best reproduce chromium evaporation behavior with atmospheres that approach either O 2 +H 2 O or Air+H 2 O with 57% H 2 O.

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“…1) 9Cr1MoVNb steel developed in the early 1980s 2) is improved in creep strength by precipitation strengthening of MX carbonitride with addition of vanadium and niobium. It has already been used widely for high temperature structural components such as header and main steam pipe of power plant.…”

Section: Introductionmentioning

confidence: 99%

Two-phase Separation of Primary MX Carbonitride during Tempering in Creep Resistant 9Cr1MoVNb Steel

et al. 2003

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Precipitation behaviour during heat treatment has been investigated on 9Cr1MoVNb steel. Coarse primary and fine secondary MX carbonitrides are observed in the as normalized condition. On the other hand, coarse primary MX is not detected after tempering at 1 038 K, and Nb-rich and V-rich fine secondary MX carbonitrides and M 23 C 6 carbide are observed in the as tempered condition. Variations of metallic elements concentrations of Nb-rich MX and V-rich MX in the as tempered condition are within the relatively small ranges. Average diameter of 34 nm for V-rich MX is slightly larger than that of 24 nm for Nb-rich MX in the as tempered condition. Both size and metallic elements concentrations of the fine secondary MX observed in the as normalized condition are almost the same as those of Nb-rich MX observed in the as tempered condition. A composition of metallic elements of the coarse primary MX varies along the line between those of Nb-rich MX and V-rich MX in a Cr-Nb-V ternary phase diagram. It has been considered that, at normalizing temperature of 1 323 K, Nb-rich MX and V-rich MX forms solid solution and composition of the primary MX varies along the tie line between those two phases. Two-phase separation of primary MX into Nb-rich MX and V-rich MX may be caused by the miscibility gap in primary MX and another two phases at the tempering temperature of 1 038 K.

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Advances in Physical Metallurgy and Processing of Steels. History of Power Plants and Progress in Heat Resistant Steels.

Cited by 478 publications

References 6 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

Calculation of Reactive-evaporation Rates of Chromia

Two-phase Separation of Primary MX Carbonitride during Tempering in Creep Resistant 9Cr1MoVNb Steel

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