Creep Deformation Behaviour and Kinetic Aspects of 9Cr-1Mo Ferritic Steel

Choudhary, B.K.; Phaniraj, C.; Rao, K. Bhanu Sankara; Mannan, S.L.

doi:10.2355/isijinternational.41.suppl_s73

Cited by 27 publications

(31 citation statements)

References 2 publications

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“…The relation can be described as p = K¢._ e s , where K¢ is the constant of proportionality. This relationship has been studied for a wide range of materials like AISI 304 stainless steel at different stress levels, [29] alpha brass [28] , and grade 9 ferritic steel [30] and found valid with a unique constant for each material. The creep deformation resistance increased with the decrease in the rate of acceleration of tertiary creep parameter 'p,' indicating that the same deformation mechanism is operating in both minimum creep deformation and tertiary stage of creep deformation.…”

Section: B Tertiary Creep Behaviormentioning

confidence: 97%

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Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic–Martensitic Steel

Vanaja

Laha

2015

Metall Mater Trans A

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Tertiary creep deformation behavior of reduced activation ferritic-martensitic (RAFM) steels having different tungsten contents has been assessed. Creep tests were carried out at 823 K (550°C) over a stress range of 180 to 260 MPa on three heats of the RAFM steel (9Cr-W-0.06Ta-0.22V) with tungsten content of 1, 1.4, and 2.0 wt pct. With creep exposure, the steels exhibited minimum in creep rate followed by progressive increase in creep rate until fracture. The minimum creep rate decreased, rupture life increased, and the onset of tertiary stage of creep deformation delayed with the increase in tungsten content. The tertiary creep behavior has been assessed based on the relationship,, considering minimum creep rate (_ e m ) instead of steady-state creep rate. The increase in tungsten content was found to decrease the rate of acceleration of tertiary parameter 'p.' The relationships between (1) tertiary parameter 'p' with minimum creep rate and time spent in tertiary creep deformation and (2) the final creep rate _ e f with minimum creep rate revealed that the same first-order reaction rate theory prevailed in the minimum creep rate as well as throughout the tertiary creep deformation behavior of the steel. A master tertiary creep curve of the steels has been developed. Scanning electron microscopic investigation revealed enhanced coarsening resistance of carbides in the steel on creep exposure with increase in tungsten content. The decrease in tertiary parameter 'p' with tungsten content with the consequent decrease in minimum creep rate and increase in rupture life has been attributed to the enhanced microstructural stability of the steel.

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Section: B Tertiary Creep Behaviormentioning

confidence: 97%

“…_ e m has been also found valid for AISI 304 stainless steel, [29] 70-30 alpha brass [28] , and grade 9 ferritic steel. [30] The near-linear variations of (1) rate of acceleration of tertiary creep 'p' with minimum creep rate (Eq. [6]) and with time spent in tertiary regime, i.e., tertiary life (t r À t t ) (Eq.…”

Section: B Tertiary Creep Behaviormentioning

confidence: 99%

Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic–Martensitic Steel

Vanaja

Laha

2015

Metall Mater Trans A

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“…The reason for the difference in values of n may arise from the presence of threshold stress, due to the interaction of dislocation with second phase particles. 8,16) Under the presence of threshold stress, σ 0 , Eq. (1) can be modified such that the applied stress is replaced by an effective stress, (σ-σ 0 ).…”

Section: )mentioning

confidence: 99%

“…Because there were no changes in the microstructure such as growth of prior austenite grain size, phase transformation of retained austenite, and growth of the precipitates. The constitutive equation to describe the deformation behavior at the high temperature used for a wide range of metallic materials such as ferritic steels, 8,21) Al, 22) Mg, 23) Sn 24) and Cu 25) alloys is generally expressed as 26,27) …”

Section: Mechanism and Constitutive Equationmentioning

confidence: 99%

“…Hence, the effect of alloying elements for high-temperature strength has been studied extensively in high Cr ferritic heat-resistant steels. [4][5][6][7][8][9][10][11][12][13][14][15][16] For example, Zhang et al 4) investigated that creep behavior such as stress and temperature dependence of creep rate in twophase alloy of Fe-15Cr-25Ni. Hamada et al 7) examined that the effect of precipitate shape of Nb(C, N) in 9Cr-1Mo steel on dispersion strengthening at elevated temperature.…”

Section: Introductionmentioning

confidence: 99%

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Improvement of High Temperature Strength by Addition of Vanadium Content of Ni–Cr–Mo Steel for Brake Discs

et al. 2017

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Improvements in the high-temperature strength are desired for the ferritic Ni-Cr-Mo steels used for the brake discs in mechanical brake systems on railway. The objective of this paper is to construct a constitutive equation for the high-temperature deformation in Ni-Cr-Mo steels containing small amounts of V. The examined steels were obtained by varying the addition of V from 0 mass% to 0.27 mass% in the steel. The flow stress of Ni-Cr-Mo steels was increased significantly by the addition of V. It was found that the creep mechanism of examined Ni-Cr-Mo steels was climb-controlled dislocation creep controlled by the lattice diffusion. Owing to the increase in the number of vanadium carbide (VC) particles with increasing the concentration of V, the threshold stress increased due to the Orowan mechanism and as a result, the high-temperature strength also increased. The constitutive equation for the high-temperature deformation of Ni-Cr-Mo steels containing small amounts of V was constructed. The constructed equation is useful in modeling the high-temperature strength under similar heat conditions in brake discs.

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Plastic Flow Behavior of an Advanced 9Cr Martensitic Heat‐Resistant Steel at High Temperatures

Gao

Zhang

2021

steel research int.

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Advanced 9Cr–1.5Mo–1Co–VNbBN martensitic steel is used for thick castings under ultra‐supercritical conditions. The microstructure, including martensitic laths, dislocations, and precipitations, is observed before and after deformation by transmission electron microscope. Steady‐state flow behavior and deformation mechanisms are investigated by analyzing strain‐rate jump test data at 600–650 °C. Results show that the plastic flow behavior of 9Cr steel is well characterized by a stress power law whose apparent stress exponent n is between 20.5 and 27.0 for the three test temperatures. The apparent activation energy of 621 kJ mol is estimated for the plastic flow of this steel, and the stress exponent and apparent activation energy are particularly high. The analysis incorporates the effect of a threshold stress, which is associated with the pinning effect of particles on dislocations. The truly modified stress exponent n0 is 4.6 at all test temperatures after removing the threshold stress, which is close to that of dislocation‐climb deformation, indicating the deformation of this steel can be described as a lattice diffusion‐controlled dislocation‐climb mechanism. Transmission electron microscopy observation is conducted to characterize the interaction of dislocation–precipitate to provide structural evidence for specific deformation mechanisms.

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Creep Deformation Behaviour and Kinetic Aspects of 9Cr-1Mo Ferritic Steel

Cited by 27 publications

References 2 publications

Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic–Martensitic Steel

Assessment of Tungsten Content on Tertiary Creep Deformation Behavior of Reduced Activation Ferritic–Martensitic Steel

Improvement of High Temperature Strength by Addition of Vanadium Content of Ni–Cr–Mo Steel for Brake Discs

Plastic Flow Behavior of an Advanced 9Cr Martensitic Heat‐Resistant Steel at High Temperatures

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