Effect of ausforming temperature on creep strength of G91 investigated by means of Small Punch Creep Tests

Vivas, Javier; Capdevila, Carlos; Altstadt, E.; Houška, M.; Serrano, Marta; De-Castro, David; San-Martín, David

doi:10.1016/j.msea.2018.05.023

Cited by 17 publications

(12 citation statements)

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“…Then, the discs were ground using a 1200 grit SiC paper down to a thickness of 500 m. For detailed information on the SPCTs the reader is referred to [13].…”

Section: Methodsmentioning

confidence: 99%

“…Tamura et al [12] demonstrated the higher effectiveness of these precipitates compared to the M23C6 carbides and lath microstructures during creep. In our previous work [13] it was shown by means of Small Punch Creep Tests (SPCT) that thermo-mechanical treatments (TMT) lead to higher creep strength compared to that obtained after applying conventional heat treatments. At the same time a reduction of creep ductility and a susceptibility to brittle fracture was observed for the thermomechanically treated steels.…”

Section: Introductionmentioning

confidence: 99%

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Microstructural Degradation and Creep Fracture Behavior of Conventionally and Thermomechanically Treated 9% Chromium Heat Resistant Steel

et al. 2018

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The microstructural degradation and the creep fracture behavior of conventionally and thermomechanically treated Grade 91 steel were investigated after performing Small Punch Creep Tests. A remarkable reduction in creep ductility was observed for the samples thermomechanically treated in comparison to those conventionally treated under the tested conditions of load (200 N) and temperature (700 ºC). A change in the fracture mechanism from a ductile transgranular fracture to a brittle intergranular fracture was observed when changing from the conventionally treated to the thermomechanically treated processing condition, leading to this drop in creep ductility. The change in the fracture mechanism was associated to the localized concentration of creep deformation, close to coarse M23C6 carbides, at the vicinity of prior austenite grain boundaries (PAGB) in the thermomechanically treated samples. The preferential recovery experienced at the vicinity of PAGB produced the loss of the lath structure and the coarsening of the M23C6 precipitates. The electron microscopy images provided suggest that the creep cavities nucleate in these weak recovered areas, associated to the presence of coarse M23C6. After the coalescence of the cavities the propagation of the cracks was facilitated by the large prior austenite grain size produced during the austenitization which favors the propagation of the cracks along grain boundaries triggering the intergranular brittle fracture. This fracture mechanism limits the potential use of the proposed thermomechanical processing routes.

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“…Then, the discs were ground using a 1200 grit SiC paper down to a thickness of 500 m. For detailed information on the SPCTs the reader is referred to [13].…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microstructural Degradation and Creep Fracture Behavior of Conventionally and Thermomechanically Treated 9% Chromium Heat Resistant Steel

et al. 2018

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“…In this work the role of ausforming temperature by selecting 600 and 900°C, at a constant deformation of 20% (Figure 4), is explored. As mentioned above, the dislocation densities were estimated by XRD in fresh martensite after each ausforming condition studied [41]. Values of (2.8 ± 0.1) × 10 15 m −2 and (1.9 ± 0.1) × 10 15 m −2 were obtained for the ausforming at 600 and 900°C, respectively.…”

Section: Effect Of Ausformingmentioning

confidence: 99%

“…The conventional treatments (AR) and TMT considered in this work were carried out on 10 mm in length and 5 mm in diameter cylindrical samples using a DIL 805A/D plastodilatometer (TA instruments) as described elsewhere [39,40]. Due to the limited amount of material available after the TMT is carried out in the plastodilatometer, the creep properties were investigated by means of the small punch creep test (SPCT) performed at 700°C as it has been previously reported [41,42]. The SPCT samples were cut transversally, from cylindrical specimens, with a thickness of 600 μm and a diameter of 8 mm.…”

Section: Creep Testsmentioning

confidence: 99%

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High-Chromium (9-12Cr) Steels: Creep Enhancement by Conventional Thermomechanical Treatments

Vivas¹,

San-Martín²,

Caballero³

et al. 2021

Welding - Modern Topics

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There is a worldwide need to develop materials for advanced power plants with steam temperatures of 700°C and above which have the capacity to achieve high efficiency and low CO 2 emissions. This request involves the development of new grades of 9-12Cr heat-resistant steels, with a nanostructured martensite, mainly focusing on the long-term creep rupture strength of base metal and welded joints, creep-fatigue properties, and microstructure evolution during exposure at such elevated temperatures. The main shortcomings of actual 9-12Cr high-chromium steels are that the creep resistance is not enough to fulfill the engineering requirements at temperatures higher than 600°C and the material undergoes a cyclic softening. Creep strength at high temperature could be improved by a microstructural optimization through nano-precipitation, guided by computational thermodynamics, and thermomechanical control process optimization.

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Stainless Steels

San-Martín

Celada-Casero

Vivas

et al. 2020

High-Performance Ferrous Alloys

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Effect of ausforming temperature on creep strength of G91 investigated by means of Small Punch Creep Tests

Cited by 17 publications

References 50 publications

Microstructural Degradation and Creep Fracture Behavior of Conventionally and Thermomechanically Treated 9% Chromium Heat Resistant Steel

Microstructural Degradation and Creep Fracture Behavior of Conventionally and Thermomechanically Treated 9% Chromium Heat Resistant Steel

High-Chromium (9-12Cr) Steels: Creep Enhancement by Conventional Thermomechanical Treatments

Stainless Steels

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