High-temperature low-cycle fatigue behavior and microstructural evolution of an ODS steel based on conventional T91

Straßberger, Luis; Chauhan, Ankur; Czink, Steffen; Aktaa, Jarir

doi:10.1016/j.ijfatigue.2017.03.012

Cited by 15 publications

(12 citation statements)

References 20 publications

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“…41 As can be seen from Figure 10, in comparison with conventional non-ODS P91, the studied ODS steels as well as ODS P91 offer comparable lifetime at higher strain amplitudes (>±0.5%) and much higher lifetime under lower strain amplitudes (<±0.5%). Similar results have been also reported by others, see Ukai and Ohtsuka 9 and Straßberger et al 14,15 However, this is not surprising since stronger materials are known to offer better cyclic strain-life under lower strain amplitudes and ductile materials are acclaimed to perform better under higher strain amplitudes. 42 This is due to the fact that strong materials resist imposed strain elastically on the basis of their strength, while ductile materials resist strain plastically on the basis of their ductility.…”

Section: Discussionsupporting

confidence: 88%

“…At present, the knowledge of LCF behaviour of ODS steels is limited since only few studies were dedicated to this issue. [8][9][10][11][12][13][14][15] However, these few studies successfully demonstrate the significance of oxide dispersion strengthening with respect to the cyclic properties. In comparison with the non-ODS variants, the ODS steels offer higher cyclic stress levels with significantly lower inelastic strain amplitudes.…”

Section: Introductionmentioning

confidence: 99%

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Towards improved ODS steels: A comparative high‐temperature low‐cycle fatigue study

Chauhan

Walter

Aktaa

2017

Fatigue Fract Eng Mat Struct

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Within the frame of this work, the mechanical behaviour of a bimodal ferritic 12Cr‐ODS steel as well as of a ferritic‐martensitic 9Cr‐ODS steel under alternating load conditions was investigated. In general, strain‐controlled low‐cycle fatigue tests at 550°C and 650°C revealed similar cyclic stress response. At elevated temperatures, the two steels manifest transitional stages, ie, cyclic softening and/or hardening corresponding to the small fraction of the cyclic life, which is followed by a linear cyclic softening stage that occupies the major fraction of the cyclic life until failure. However, it is clearly seen that the presence of the nano‐sized oxide particles is certainly beneficial, as the degree of cyclic softening is significantly reduced compared with non‐ODS steels. Besides, it is found that both applied strain amplitude and testing temperature show a strong influence on the cyclic stress response. It is observed that the degree of linear cyclic softening in both steels increases with increasing strain amplitude and decreasing test temperature. The effect of temperature on inelastic strain and hence lifetime becomes more pronounced with decreasing applied strain amplitude. When analysing the lifetime behaviour of both ODS steels in terms of inelastic strain energy calculations, it is found that comparable inelastic strain energies lead to similar lifetimes at 550°C. At 650°C, however, the higher inelastic strain energies of 12Cr‐ODS steel result in significant lower lifetimes compared with those of the 9Cr‐ODS steel. The strong degradation of the cyclic properties of the 12Cr‐ODS steel is obviously linked to the fact that the initial hardening response appears significantly more pronounced at 650°C than at 550°C. Finally, the obtained results depict that the 9Cr‐ODS steel offers higher number of cycles to failure at 650°C, compared with other novel ODS steels described in literature.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Towards improved ODS steels: A comparative high‐temperature low‐cycle fatigue study

Chauhan

Walter

Aktaa

2017

Fatigue Fract Eng Mat Struct

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“…(3) Compared to conventional steels, ODS steels have a better fatigue and creep resistance. As a consequence, they can be operated at higher temperatures, which would substantially reduce irradiation hardening [21][22][23]. In addition, 9Cr-ODS steels show higher uniform elongations under irradiation, which extends certain design ranges when applying codes such as RCC-MRx [17,24,25].…”

Section: Introductionmentioning

confidence: 96%

Technological Processes for Steel Applications in Nuclear Fusion

et al. 2021

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Plasma facing components for energy conversion in future nuclear fusion reactors require a broad variety of different fabrication processes. We present, along a series of studies, the general effects and the mutual impact of these processes on the properties of the EUROFER97 steel. We also consider robust fabrication routes, which fit the demands for industrial environments. This includes heat treatment, fusion welding, machining, and solid-state bonding. Introducing and following a new design strategy, we apply the results to the fabrication of a first-wall mock-up, using the same production steps and processes as for real components. Finally, we perform high heat flux tests in the Helium Loop Karlsruhe, applying a few hundred short pulses, in which the maximum operating temperature of 550 °C for EUROFER97 is finally exceeded by 100 K. Microstructure analyses do not reveal critical defects or recognizable damage. A distinct ferrite zone at the EUROFER/ODS steel interface is detected. The main conclusions are that future breeding blankets can be successfully fabricated by available industrial processes. The use of ODS steel could make a decisive difference in the performance of breeding blankets, and the first wall should be completely fabricated from ODS steel or plated by an ODS carbon steel.

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“…In these previous studies, the damage accumulation was assumed to be linear to the number of cycles, and Miner’s rule and the formula for the linear fatigue cumulative damage was applied [ 6 ]. In order to reflect the physical process and the corresponding mechanism, researchers tried applying different parameters to measure the damage of metals after cyclic loading from different angles [ 7 , 8 , 9 , 10 , 11 ]. Mesmacque et al proposed that the degree of strength degradation of a material could be used to measure its damage [ 12 ].…”

Section: Introductionmentioning

confidence: 99%

Remaining Life Assessment for Steel After Low-Cycle Fatigue by Surface Crack Image

et al. 2019

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After pre-fatigue cycles at different strain amplitudes with different N/Nf values (33.3%, 50%, and 75%), specimens of HRB335 steel were subjected to uniaxial tension until failure. By this method the mechanical properties of the specimens after pre-fatigue testing were measured, and the fracture morphology and microscopic morphology in the vicinity of the specimen’s neck surface near the fracture were observed. The verification of the characteristics to be used to estimate the damage caused during the loading cycles was conducted. By observing optical microscope images of the surface area near the neck of the specimens, it was found that the images of surface cracks were significantly different and strongly depended on the number of pre-fatigue cycles the specimen had undergone. In response to this phenomenon, both the microscopic images taken directly from the photos of the surface crack distribution and the binary images based on them were statistically analyzed, and then a parameter, S, denoted as the “unit crack area”, characterizing the cumulative fatigue damage was suggested. Furthermore, the test procedure and the calculation formula for determining the image parameters were summarized, and a method for evaluating the remaining life of steel after low-cycles of reversed tension and compression was proposed.

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High-temperature low-cycle fatigue behavior and microstructural evolution of an ODS steel based on conventional T91

Cited by 15 publications

References 20 publications

Towards improved ODS steels: A comparative high‐temperature low‐cycle fatigue study

Towards improved ODS steels: A comparative high‐temperature low‐cycle fatigue study

Technological Processes for Steel Applications in Nuclear Fusion

Remaining Life Assessment for Steel After Low-Cycle Fatigue by Surface Crack Image

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