On the 650 °C thermostability of 9–12Cr heat resistant steels containing different precipitates

Wu, Hai Yan; Yan, Wei; Zwaag, Sybrand van der; Shi, Quanqiang; Wang, Wei; Yang, Ke; Shan, Yiyin

doi:10.1016/j.actamat.2017.05.069

Cited by 67 publications

(16 citation statements)

References 32 publications

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“…The initial decrease is unlikely due to precipitate coarsening, given the stable precipitate size shown in Figure 7. Instead, the transition from martensitic to ferritic microstructure could account for the hardness decrease, as reported by Wang et al [38] The trend indicated by the dashed line in Figure 10 suggests that, the transition ends after aging for a few hundred hours. The hardness remains constant up to 3000 hours afterwards.…”

Section: B Mechanical Propertiessupporting

confidence: 56%

“…[27][28][29] Low-carbon concentrations are known to suppress or eliminate M 23 C 6 formation for improved microstructural stability. [34][35][36][37][38] For instance, Taneike and coworkers [34] studied the effect of C concentration and found that lower C concentration gives rise to longer rupture time. Another approach is the use of coherent B2-NiAl precipitates for improved microstructure stability.…”

Section: Introductionmentioning

confidence: 99%

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Design and Characterization of a Heat-Resistant Ferritic Steel Strengthened by MX Precipitates

Zhang

et al. 2019

Metall Mater Trans A

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The long-term performance of current heat-resistant ferritic steels used in steam generators is primarily limited by microstructure degradation as a result of coarsening or transformation of precipitates. To improve the microstructural stability, a heat-resistant ferritic steel was designed via computational thermodynamics to exclusively contain metal carbonitride (MX) precipitates as the primary means for strengthening at elevated temperatures. The volume fraction of precipitates is 0.35 vol pct, about one-seventh of P91. These MX precipitates are either V-rich or Nb-rich with plate-like or spheroidal morphology, respectively. The precipitate size remains almost constant at 973 K for up to 3000 hours aging. Electron diffraction analysis revealed a Baker-Nutting orientation relationship between the precipitate and the matrix. Consistent with the thermodynamics-based design, M 23 C 6-, Laves-, and Z phase were not detected. The creep threshold stress, derived from high-temperature compressive creep tests, are evaluated to be 63 ± 1 and 43 ± 2 MPa at 923 K and 973 K, respectively, on par with or slightly better than P91. This study reveals that MX precipitates in ferritic steels coarsen slowly at temperatures up to 973 K and that a relatively small volume fraction of MX precipitates can provide effective long-term creep performance at elevated temperatures.

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Section: B Mechanical Propertiessupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Design and Characterization of a Heat-Resistant Ferritic Steel Strengthened by MX Precipitates

Zhang

et al. 2019

Metall Mater Trans A

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“…The microstructure evolution during long-term aging and creep of high Cr steels can be described by the following parameter [48]:…”

Section: Creep/aging Softeningmentioning

confidence: 99%

Creep behavior and microstructural evolution of a 9%Cr steel with high B and low N contents

Tkachev

Belyakov

Kaibyshev

2018

Materials Science and Engineering: A

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A B S T R A C TThe creep behavior of a 3%Co modified P92-type steel with high content of boron and low content of nitrogen was studied. The precipitation of Laves phase at lath boundaries provides a rapid decrease in the strain rate during transient creep. The finely dispersed (V,Nb)(C,N) carbonitrides uniformly distributed throughout and M 23 C 6 carbides located at various boundaries/subboundaries result in extended steady-state creep. Gradual coarsening and an increase in the volume fraction of M 23 C 6 carbides as well as coarsening of Laves phase particles is accompanied by an increase in the lath size during the steady-state creep. The coarsening of lath structure that is assisted by the dissolution of Laves phase particles at lath boundaries during steady-state creep leads to the onset of tertiary creep with a highly accelerated rate. The well-developed subgrain structure is observed in the ruptured samples, whereas the distance between high-angle boundaries does not change during the creep.

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“…Although the precipitation of Laves phases can compensate the degradation of creep-rupture properties caused by the weakening of solid solution strengthening effects from W and Mo atoms in a relatively short time, but the aggregation and coarsening of Laves phases accompanied with the long-term thermal aging and creep can lead to the creep-rupture performance degradation 13 , 14 . The M 23 C 6 carbide is an important factor that maintains the lath structure stability of the tempered martensite in high Cr ferritic heat-resistant steels 15 , 16 . Differently from the short-time precipitation characteristics of all M 23 C 6 carbides, MX phases and Laves phases, the precipitation of Z phases generally requires a relatively long thermal aging time.…”

Section: Introductionmentioning

confidence: 99%

Effects of Precipitates Evolution on Low Stress Creep Properties in P92 Heat-resistant Steel

Han

Shen

Xie

2018

Sci Rep

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The evolution of precipitates in P92 heat-resistant steel sustained under thermal aging at 923 K for different times were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the effects of precipitates evolution on the low stress creep properties were experimentally analyzed through uniaxial creep testing and multiaxial “helicoid spring creep testing”. The results demonstrate that the coarsening of M23C6 carbide is significantly slower than the Laves phase in the thermal aging of 0~8000 h. The creep resistance of the P92 heat-resistant steel is enhanced at 923 K aging for 3000 h, and the strengthening effect is significantly apparent under the lower stresses. Moreover, the microstructure degradation factor of the P92 heat-resistant steel in the low stress region at 923 K is different that under the lower stresses of 20 MPa and 35 MPa is mainly Laves phase and the higher stresses of 65 MPa and 75 MPa is mainly M23C6 carbide.

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On the 650 °C thermostability of 9–12Cr heat resistant steels containing different precipitates

Cited by 67 publications

References 32 publications

Design and Characterization of a Heat-Resistant Ferritic Steel Strengthened by MX Precipitates

Design and Characterization of a Heat-Resistant Ferritic Steel Strengthened by MX Precipitates

Creep behavior and microstructural evolution of a 9%Cr steel with high B and low N contents

Effects of Precipitates Evolution on Low Stress Creep Properties in P92 Heat-resistant Steel

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