Microstructure and long-term creep properties of 9–12% Cr steels

Hald, John

doi:10.1016/j.ijpvp.2007.06.010

Cited by 386 publications

(159 citation statements)

References 14 publications

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“…11). This indicates that the MX carbonitrides were not significantly changed in size during short-term creep, which is consistent with existing observations of MX carbonitrides being more resistant to coarsening than M 23 C 6 during creep exposure [19,54]. The stable MX precipitates enhance the creep resistance of the MarBN steel by improving the stability of the dislocation structure [31,55].…”

Section: Microstructural Characterisation Of Creep Exposed Materialssupporting

confidence: 89%

Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures

Benaarbia

Sun

et al. 2018

Materials Science and Engineering: A

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This paper reports the short-term creep behaviour at elevated temperatures of a MarBN steel variant. Creep tests were performed at three different temperatures (625°C, 650°C and 675°C) with applied stresses ranging from 160 MPa to 300 MPa, and failure times from 1 to 350 h. Analysis of the macroscopic creep data indicates that the steady-state creep exhibits a power-law stress dependence with an exponent of 7 and an activation energy of 307 kJ mol, suggesting that dislocation climb is the dominant rate-controlling creep mechanism for MarBN steel. Macroscopic plastic instability has also been observed, highlighted by an obvious necking at the rupture region. All the macroscopic predictions have been combined with microstructural data, inferred from an examination of creep ruptured samples, to build up relations between macroscopic features (necking, damage, etc.), and underlying microstructural mechanisms. Analysis of the rupture surfaces has revealed a ductile fracture mode. Electron Backscatter Diffraction (EBSD) analysis near to the rupture surface has indicated significant distortion and refinement of the original martensitic substructure, which is evidence of long-range plastic flow. Dislocation pile-ups and tangles from TEM were also observed near substructure boundaries and precipitate particles. All of these microstructural observations suggest that creep is influenced by a complex interaction between several elements of the microstructure, such as dislocations, precipitates and structure boundaries. The calculated stress exponent and activation energy have been found to agree quantitatively with the highlighted microstructural features, bearing some relationships to the true observed creep microstructures.

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Section: Microstructural Characterisation Of Creep Exposed Materialssupporting

confidence: 89%

Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures

Benaarbia

Sun

et al. 2018

Materials Science and Engineering: A

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“…These particles were identified as a Laves phase rich in Mo and W; the precipitation of this phase in the 9 % Cr steel was described by several authors. [1][2][3][4][5][6][7] The phase composition was verified by element mapping (Figure 3). It is apparent that the observed phases contain high amounts of both tungsten and molybdenum, while the chromium content is reduced compared to the surrounding material.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3] A combination of a specific chemical composition and a suitable heat treatment provides these materials with a creep strength of up to 100 MPa at 600°C (after 10 5 h) or even higher. 4 Their operation temperature is limited to about 620°C; however, the possibilities of increasing it up to 650°C are being studied.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the structural changes in 9 % Cr creep-resistant steel using an electrochemical technique

Rapouch¹,

Bystrianský²,

Šefl³

2015

Mater. Tehnol.

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A correct prediction of the remaining lifetime of the components for power plants requires an evaluation of the material structural stability. In this work, the possibility of a non-destructive evaluation of the structural changes in 9 % Cr creep-resistant steel P92 after a long-term annealing was investigated using the electrochemical-polarization technique. Aging at 650°C caused a significant precipitation and coarsening processes resulting in a redistribution of some alloying elements in the structure. The structural changes confirmed by scanning-electron-microscopy observations and a hardness measurement affected the shape of the measured potentiodynamic curves. Significant local peaks on this curve, in the active-to-passive transition area and in the transpassive region, were evaluated. Characteristic current densities in these regions showed very good correlation with the results of the structure observation and hardness testing. Keywords: 9 % Cr creep-resistant steel, structural changes, electrochemical detection, polarization curve Pravilna napoved preostale trajnostne dobe komponent v termoelektrarnah zahteva oceno stabilnosti strukture materiala. V tem delu je bila preiskovana mo`nost neporu{ne ocene sprememb v strukturi jekla z 9 % Cr, odpornega proti lezenju, z uporabo tehnike elektrokemijske polarizacije. Staranje pri 650°C je povzro~ilo mo~no izlo~anje in procese rasti, kar je povzro~ilo prerazporeditev nekaterih legirnih elementov v strukturi. Spremembe v strukturi, potrjene pri opazovanju z vrsti~nim elektronskim mikroskopom in pri merjenju trdote, so vplivale na obliko izmerjenih potenciodinami~nih krivulj. Ocenjeni so bili lokalni vrhovi na tej krivulji v obmo~ju prehoda iz aktivnega v pasivno in v transpasivnem obmo~ju. Zna~ilna gostota tokov v teh obmo~jih je pokazala dobro ujemanje z rezultati opazovanja strukture in z meritvami trdote. Klju~ne besede: jeklo z 9 % Cr, odporno proti lezenju, spremembe strukture, elektrokemi~na detekcija, polarizacijska krivulja

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“…Even though MX precipitates are stable and do not coarsens heavily during creep exposure [19,20]. However, it is found that they might dissolve and form complex nitride Z-phase under long-term creep exposure [21]. Z-phase, Cr(V,Nb)N, is another nitride precipitate with similar elements as the MX.…”

Section: Precipitatesmentioning

confidence: 99%

Heat-Resistant Steels, Microstructure Evolution and Life Assessment in Power Plants

Hu¹

2012

Thermal Power Plants

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Microstructure and long-term creep properties of 9–12% Cr steels

Cited by 386 publications

References 14 publications

Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures

Investigation of short-term creep deformation mechanisms in MarBN steel at elevated temperatures

Evaluation of the structural changes in 9 % Cr creep-resistant steel using an electrochemical technique

Heat-Resistant Steels, Microstructure Evolution and Life Assessment in Power Plants

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