Microstructure and creep behaviour of P92 steel after HPT

Král, Pétr; Dvořák, Jiří; Sklenička, V.; Masuda, Takahiro; Horita, Zenji; Kuchařová, K.; Kvapilová, Marie; Svobodová, Marie

doi:10.1016/j.msea.2018.03.059

Cited by 32 publications

(27 citation statements)

References 39 publications

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“…It is generally accepted that the rotation of grains due to sliding along boundaries leads to the formation of random orientations (weakening of texture). However, Kral et al [ 38 ] observed that the microstructure of UFG P92 steel after creep exhibited a relatively strong texture in the gauge length that was inherited from the HPT-processed state. The experimentally-measured data for UFG P92 steel were shifted to significantly slower strain rates in comparison with the GBS mechanism (Equation (A1)).…”

Section: Discussionmentioning

confidence: 99%

“…Thus, grain boundaries are an important structure constituent influencing creep behaviour, especially in nano or UFG materials [ 35 , 36 , 37 ]. Our previous work [ 38 ] revealed that 1 HPT revolution at room temperature leads to the saturation of microstructure characteristics in UFG P92 steel at an equivalent strain higher than 20. It was shown that P92 steel with a UFG microstructure accelerates the formation of the Laves phase during creep in comparison with a coarse-grained state.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Ultrafine-Grained Microstructure on Creep Behaviour of 9% Cr Steel

et al. 2018

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The effect of ultrafine-grained size on creep behaviour was investigated in P92 steel. Ultrafine-grained steel was prepared by one revolution of high-pressure torsion at room temperature. Creep tensile tests were performed at 873 K under the initially-applied stress range between 50 and 160 MPa. The microstructure was investigated using transmission electron microscopy and scanning electron microscopy equipped with an electron-back scatter detector. It was found that ultrafine-grained steel exhibits significantly faster minimum creep rates, and there was a decrease in the value of the stress exponent in comparison with coarse-grained P92 steel. Creep results also showed an abrupt decrease in the creep rate over time during the primary stage. The abrupt deceleration of the creep rate during the primary stage was shifted, with decreasing applied stress with longer creep times. The change in the decline of the creep rate during the primary stage was probably related to the enhanced precipitation of the Laves phase in the ultrafine-grained microstructure.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Ultrafine-Grained Microstructure on Creep Behaviour of 9% Cr Steel

et al. 2018

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“…Constant load tensile creep tests were conducted at 873 K (~0.48 of melting temperature) in protective argon atmosphere using flat specimens with a gauge length of 10 mm and a cross section of 3 × 1 mm 2 . The tested HPT specimens were manufactured from the disc region with equivalent strain of about 25 ± 5 [ 12 , 21 ]. The gauge lengths of the HPS tensile specimens were taken from the central part of the sheet.…”

Section: Methodsmentioning

confidence: 99%

The Effect of Predeformation on Creep Strength of 9% Cr Steel

et al. 2020

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Martensitic creep-resistant P92 steel was deformed by different methods of severe plastic deformation such as rotation swaging, high-pressure sliding, and high-pressure torsion at room temperature. These methods imposed significantly different equivalent plastic strains of about 1–30. It was found that rotation swaging led to formation of heterogeneous microstructures with elongated grains where low-angle grain boundaries predominated. Other methods led to formation of ultrafine-grained (UFG) microstructures with high frequency of high-angle grain boundaries. Constant load tensile creep tests at 873 K and initial stresses in the range of 50 to 300 MPa revealed that the specimens processed by rotation swaging exhibited one order of magnitude lower minimum creep rate compared to standard P92 steel. By contrast, UFG P92 steel is significantly softer than standard P92 steel, but differences in their strengths decrease with increasing stress. Microstructural results suggest that creep behavior of P92 steel processed by severe plastic deformation is influenced by the frequency of high-angle grain boundaries and grain coarsening during creep.

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“…If one starts to deform the material with grain size of several millimetres, it quickly decreases down to few hundreds of nanometers. Then, the grain size reaches the steady-state value, stabilises and does not decrease anymore [17,[26][27][28][29]. In the same material, the steady-state grain size depends first of all on the SPD mode.…”

Section: Steady-state During Spdmentioning

confidence: 96%

Diffusive and Displacive Phase Transformations Under High Pressure Torsion

Straumal

Kilmametov

Мазилкин

et al. 2019

Acta Metall Slovaca

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<p class="AMSmaintext"><span lang="EN-GB">Severe plastic deformation (SPD) can induce various phase transformations. After a certain strain, the dynamic equilibrium establishes between defects production by an external force and their relaxation (annihilation). The grain size, hardness, phase composition etc. in this steady-state does not depend on the initial state of a material and is, therefore, equifinal. In this review we discuss the competition between precipitation and dissolution of precipitates, amorphization and (nano)crystallization, SPD-induced accelerated mass-transfer, allotropic and martensitic transitions and formation of grain boundary phases.</span></p>

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Microstructure and creep behaviour of P92 steel after HPT

Cited by 32 publications

References 39 publications

The Effect of Ultrafine-Grained Microstructure on Creep Behaviour of 9% Cr Steel

The Effect of Ultrafine-Grained Microstructure on Creep Behaviour of 9% Cr Steel

The Effect of Predeformation on Creep Strength of 9% Cr Steel

Diffusive and Displacive Phase Transformations Under High Pressure Torsion

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