Transition from power-law to viscous creep behaviour of p-91 type heat-resistant steel

Kloc, L.; Sklenička, V.

doi:10.1016/s0921-5093(97)00364-x

Cited by 72 publications

(55 citation statements)

References 9 publications

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“…It can be seen that these values are much higher and do not reflect the true value of the activation energy. Higher apparent creep activation energies for different high strength Cr-Mo steels have also been reported by different studies [39,40].…”

Section: Creep Behaviour Analysissupporting

confidence: 67%

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: Creep Behaviour Analysissupporting

confidence: 67%

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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“…In [9][10][11] the testing facilities and experimental data for a 9% Cr steel are presented. Creep tests for the stress levels below 20 MPa were performed by the use of helical springs while for the stress levels over approx.…”

Section: Secondary Creep Constitutive Equationmentioning

confidence: 99%

“…Figure 2b shows the experimental data for the temperature 600 • C. In contrast to the previous example, the nearly linear creep range can be identified, while the data are not enough to capture the transition range. It was suggested in [9] that the linear creep sharply changes to the power law regime as the stress exceeds a certain transition value. Figure 2b shows that the model (1) describes well both the viscous and the power law creep ranges.…”

Section: Secondary Creep Constitutive Equationmentioning

confidence: 99%

Creep analysis with a stress range dependent constitutive model

2009

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Many materials exhibit the stress range dependent creep behavior. The power law creep observed for a certain stress range changes to the viscous type creep as the stress value decreases. Recently published experimental data for advanced heat resistant steels indicate that the high creep exponent (in the range 7-12) may decrease to the low value of approximately unity within the stress range relevant for engineering structures. The aim of this paper is to analyze the influence of the stress range dependent power-law-viscous creep transition on the behavior of structures at elevated temperature. A constitutive model for the minimum creep rate is introduced to describe both the linear and the power law creep depending upon the stress level. To demonstrate basic features of the stress range dependent creep modeling, several elementary examples from structural mechanics are presented. They include a stress relaxation problem, a beam subjected to pure bending and a pressurized thick-walled cylinder. Based on the uni-axial transition stress the transition value of the external load is estimated such that above this value the power law can be applied. For the loading levels below this value the character of the stress distribution as well as the stress values are essentially influenced by the viscous creep.

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“…To describe creep flow in the low stress regime, data from Kloc and Sklenička (1997) who carried out creep tests on helicoidal spring specimens machined in another type of P91 steel (having nearly the same chemical composition and normalising treatment of 1 h at 1060 • C followed by a tempering of 2 h at 750 • C) were then added to the database. One can note that creep strain rates at high stresses from Kloc and Sklenička (1997) well agree with the results of the present study. Results of Figure 3 suggest that at high stresses, the deformation mechanism is dominated by dislocation cross-slip or climb, while for stresses below 70 MPa it is dominated by grain boundary diffusion.…”

Section: Creep Flow Propertiesmentioning

confidence: 99%

Creep failure model of a tempered martensitic stainless steel integrating multiple deformation and damage mechanisms

2005

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International audienceA new model considering both deformation and damage evolution under multiple viscoplastic mechanisms is used to represent high temperature creep deformation and damage of a martensitic stainless steel in a wide range of load levels. First, an experimental database is built to characterise both creep flow and damage behaviour using tests on various kinds of specimens. The parameters of the model are fitted to the results and to literature data for long term creep exposure. An attempt is made to use the model to predict creep time to failure up to 105 h

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Transition from power-law to viscous creep behaviour of p-91 type heat-resistant steel

Cited by 72 publications

References 9 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

Creep analysis with a stress range dependent constitutive model

Creep failure model of a tempered martensitic stainless steel integrating multiple deformation and damage mechanisms

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