Comparison of low-cycle fatigue behaviors between two nickel-based single-crystal superalloys

Li, P.; Li, Q.Q.; Jin, Tao; Zhou, Yu; Li, J.G.; Sun, Xiaofeng; Zhang, Z.F.

doi:10.1016/j.ijfatigue.2014.01.018

Cited by 67 publications

(24 citation statements)

References 48 publications

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“…Because of this unique microstructure, superalloys exhibit unique temperature-dependent strength properties under simple monotonic loading [2][3][4][5][6]. On the other hand, because these superalloy components are subjected to cyclic thermal stresses resulting from startup and shutdown, mechanical fatigue has been an area of ever-growing interest for the past several decades [7][8][9][10]. Compared to low-cyclic fatigue (LCF), thermomechanical fatigue (TMF) can approach the real conditions of these superalloys during service and evaluate fatigue damage effectively.…”

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confidence: 99%

“…Planar slip is considered as a dominant deformation mode at room temperature (RT), and the slipping dislocations are restricted in the parallel slip bands (SBs) [11,12]. Li et al [7] found that the dislocation configuration became homogeneous with increasing temperature, and the SBs gradually disappeared. However, Petrenec et al [13] found that the SBs are always present across the entire medium-temperature range (600-800°C).…”

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“…2a). The formation of these SFs in the c 0 phase during LCF deformation has been widely reported [7][8][9]. However, the SFs present in the c matrix have been rarely reported previously, particularly at low temperature (e.g.…”

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confidence: 99%

“…2a) is good evidence for the above conclusion. This SB mainly consists of a high density of tangled dislocations planar slipping in the matrix and continuously cutting through the c 0 phase [7,13]. A number of ladder-like structural SBs parallel to the {111} slip planes have been reported at RT [7,13].…”

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Deformation mechanisms of a nickel-based single-crystal superalloy during low-cycle fatigue at different temperatures

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Deformation mechanisms of a nickel-based single-crystal superalloy during low-cycle fatigue at different temperatures

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“…N-type rafts do not stop the propagation of fatigue crack as well as P-type rafts do. According to Li et al [63,64], alloying with Re retards the rafting process during LCF which in their study proved to be beneficial for the fatigue life. Regarding the TMF properties, Neuner et al [65] have shown that the pre-rafting of the microstructure seems to influence the fatigue life differently, depending on which TMF cycle is used.…”

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confidence: 98%

On Thermomechanical Fatigue of Single-Crystal Superalloys

Segersäll¹

2014

Linköping Studies in Science and Technology. Dissertations

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Thesis cover: Design by Maria J. SegersällPrinted by: LiU-Tryck, Linköping, Sweden, 2014 ISBN 978-91-7519-211-6 ISSN 0345-7524 Distributed by: Division of Engineering Materials, Department of Management and Engineering Linköping University SE-58183, Linköping, Sweden © 2014 Mikael SegersällThis document was prepared with L A T E X, October 17, 2014 AbstractThanks to their excellent mechanical and chemical properties at temperatures up to 1000°C, nickel-based superalloys are used in critical components in high-temperature applications such as gas turbines and aero engines. One of the most critical components in a gas turbine is the turbine blade, and to improve the creep and fatigue properties of this component, it is sometimes cast in single-crystal form rather than in the more conventional polycrystalline form. Gas turbines are most commonly used for power generation and the turbine efficiency is highly dependent on the performance of the superalloys.Today, many gas turbines are used as a complement for renewable energy sources, for example when the wind is not blowing or when the sun is not shining, which means that the turbine runs differently compared to earlier, when it ran for longer time periods with a lower number of start-ups and shutdowns. This new way of running the turbine, with an increased number of start-ups and shut-downs, results in new conditions for critical components, and one way to simulate these conditions is to perform thermomechanical fatigue (TMF) testing in the laboratory. During TMF, both mechanical strain and temperature are cycled at the same time, and one fatigue cycle corresponds to the conditions experienced by the turbine blade during one start-up and shut-down of the turbine engine.In the work leading to this PhD thesis, TMF testing of single-crystal superalloys was first performed in the laboratory and this was then followed microstructure investigations to study the occurring deformation and damage mechanisms. Specimens with different crystallographic directions have been tested in order to investigate the anisotropic behaviour shown by these materials. Results show a significant orientation dependence during TMF in which specimens with a low elastic stiffness perform better. However, it is also shown that specimens with a higher number of active slip systems perform better during TMF compared to specimens with less active slip sysiii tems. This is because a higher number of active slip systems results in a more widespread deformation and seems to be beneficial for the TMF life. Further, microscopy shows that the deformation during TMF is localised to several deformation bands and that different deformation and damage mechanisms prevail according to in which crystal orientation the material is loaded. Deformation twinning is shown to be a major deformation mechanism during TMF and the interception of twins seems to trigger recrystallization. This is certainly negative for the mechanical properties of single-crystal superalloys since no grain boundary strengthening elemen...

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Low Cycle Fatigue Failure Analysis of a Ni‐Based Single Crystal Superalloys at 850 °C

et al. 2018

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This paper presents a low cycle fatigue (LCF) failure analysis on [001], [011], and [111] orientations of a Ni‐based single crystal superalloys at 850 °C. Fracture mechanism and microstructure damage evolution are revealed through crystal plastic theory and fracture morphology analysis. Strain‐controlled LCF tests are conducted with the standard round bar samples; the fracture morphology and microstructure characteristics, such as the fracture mechanism and microstructure damage evolution, are observed via scanning electron microscopy (SEM), optical microscopy (OM). Crystal plastic theory is adopted to establish the crystal slip system framework, considering elastic and plastic strain rate, elastic orientation factors, and the resolved shear stress (Rss). The life prediction model is established based on Levkovitch damage theory, theoretical analysis, and test results has good consistency. The results demonstrate that fatigue life on [001] orientation is the longest, but considering the effects of stress amplitude and Young's modulus, [011] orientation exhibits the best fatigue performance. Under LCF loading, the initial crack starts to occur on surface of specimen if the internal defects are small and negligible; in contrast the initial crack starts to occur in subsurface or internal of specimen if the microstructure defects exist in material. The LCF cross‐section of SC belongs to the quasi‐cleavable type, the crack propagates in the direction of {111} plane and then extends along the vertical stress axis until the specimen fractures.

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Comparison of low-cycle fatigue behaviors between two nickel-based single-crystal superalloys

Cited by 67 publications

References 48 publications

Deformation mechanisms of a nickel-based single-crystal superalloy during low-cycle fatigue at different temperatures

Deformation mechanisms of a nickel-based single-crystal superalloy during low-cycle fatigue at different temperatures

On Thermomechanical Fatigue of Single-Crystal Superalloys

Low Cycle Fatigue Failure Analysis of a Ni‐Based Single Crystal Superalloys at 850 °C

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