Thermomechanical fatigue mechanism in a modern single crystal nickel base superalloy TMS-82

Zhang, J.X.; Harada, Hiroshi; Ro, Y.; Koizumi, Yutaka; Kobayashi, Toshiharu

doi:10.1016/j.actamat.2008.02.035

Cited by 99 publications

(49 citation statements)

References 31 publications

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“…The reader is referred to section 5.1 for further information regarding different TMF cycles. It has also been shown that oxidation plays an important role in assisting crack propagation in superalloys during TMF, see for example [91,92]. …”

Section: Oxidationmentioning

confidence: 99%

“…It was found that a significant tension/compression asymmetry in creep relaxation is prevalent and that the degree of asymmetry changed between the different directions. Zhang et al [91] studied the microstructure evolution during TMF testing with a 1 h dwell-time and subsequently divided the TMF test into three stages: (i) primary creep relaxation where dislocations fill the γ-channels and cut the γ -cuboids; (ii) secondary steady state creep relaxation where the dislocations formed during the tensile deformation are eliminated; and (iii) tertiary creep relaxation where de-twinning of deformation twins occurs. Hirsch et al [98] applied a superimposed high-cycle fatigue waveform during the dwell-time of the TMF cycle, and this influenced the TMF life significantly due to a change in mean stress.…”

Section: Thermomechanical Fatigue: a Literature Reviewmentioning

confidence: 99%

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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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Section: Oxidationmentioning

confidence: 99%

Section: Thermomechanical Fatigue: a Literature Reviewmentioning

confidence: 99%

On Thermomechanical Fatigue of Single-Crystal Superalloys

Segersäll¹

2014

Linköping Studies in Science and Technology. Dissertations

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“…This process must result in a stress relaxation and be related with the cyclic softening behavior. 31,32) The cyclic softening may be due to the loss of coherency due to coarsening of £ A precipitates. 33,34) The cyclic softening behavior is also related with the high temperature which is above 40% of the melting temperature of superalloys, therefore creep and relaxation and effects such as ageing of superalloys and instabilities of the precipitates can occur.…”

Section: Dislocation Structures and Deformation Mechanismmentioning

confidence: 99%

Fatigue Behavior and Life Prediction Model of a Nickel-Base Superalloy under Different Strain Conditions

et al. 2016

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The fatigue behavior of a nickel-base superalloy was investigated under total strain-controlled mode at high temperature. The fatigue life, cyclic stress response behavior and hysteresis loop of the superalloy were investigated under isothermal low cycle fatigue (LCF) conditions. The superalloy exhibited cyclic hardening and softening behaviors during the process of fatigue loading. The hysteresis loop shifted downwards slightly with the increase of the number of cycles. The fatigue life under different strain amplitudes reflects the interactions of dislocations and £ A precipitates at elevated temperature. Three life prediction models to evaluate the fatigue life of the superalloy were evaluated for the LCF tests. The prediction values obtained by Manson-Coffin relationship agree well with the experimental results. The mechanisms of LCF were revealed through the observation of the microstructures by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The main deformation mechanism of the superalloy is the different interactions between dislocations and £ A precipitates.

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“…In gas turbine system utilized in an electric power plant, R&D has been done extensively to reach a high overall efficiency (Ref [1][2][3][4][5][6]. Efficiency in gas turbine plant can be achieved easily by the increase of turbine inlet temperature (TIT), which also brings about the increase of metal temperature in the components of gas turbine such as a first-stage blade.…”

Section: Introductionmentioning

confidence: 99%

Porous Ceramic Coating for Transpiration Cooling of Gas Turbine Blade

Arai

Suidzu

2013

J Therm Spray Tech

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A transpiration cooling system for gas turbine applications has significant benefit for reducing the amount of cooling air and increasing cooling efficiency. In this paper, the porous ceramic coating, which can infiltrate cooling gas, is developed with plasma spraying process, and the properties of the porous coating material such as permeability of cooling gas, thermal conductivity, and adhesion strength are examined. The mixture of 8 wt.% yttria-stabilized zirconia and polyester powders was employed as the coating material, in order to deposit the porous ceramic coating onto Ni-based super alloy substrate. It was shown that the porous ceramic coating has superior permeability for cooling gas. The adhesion strength of the porous coating was low only 20% compared with the thermal barrier coating utilized in current gas turbine blades. Simulation test of hot gas flow around the gas turbine blade verified remarkable reduction of the coating surface temperature by the transpiration cooling mechanism. It was concluded that the transpiration cooling system for the gas turbine could be achieved using the porous ceramic coating developed in this study.

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Thermomechanical fatigue mechanism in a modern single crystal nickel base superalloy TMS-82

Cited by 99 publications

References 31 publications

On Thermomechanical Fatigue of Single-Crystal Superalloys

On Thermomechanical Fatigue of Single-Crystal Superalloys

Fatigue Behavior and Life Prediction Model of a Nickel-Base Superalloy under Different Strain Conditions

Porous Ceramic Coating for Transpiration Cooling of Gas Turbine Blade

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