Fatigue crack growth behaviour of an alternative single crystal nickel base superalloy

Palmert, Frans; Gustafsson, David; Busse, Christian

doi:10.1016/j.ijfatigue.2017.12.003

Cited by 30 publications

(12 citation statements)

References 32 publications

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“…This was explained by the fact that the shear strength of the γ , which are sheared during crystallographic crack growth, increases with rising temperatures. A study by Palmert et al [37] on the alloy examined in this work showed that it exhibits the highest propensity for crystallographic crack growth at 500 • C rather than at higher or lower temperatures. The nature of this phenomenon is still under investigation.…”

Section: Characteristic Fracture Behaviour Of Single-crystalsmentioning

confidence: 60%

Modelling of Crack Growth in Single-Crystal Nickel-Base Superalloys

Busse

2019

Linköping Studies in Science and Technology. Dissertations

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No part of this publication may be reproduced, stored in a retrieval system, or be transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior permission of the author. Thank you! Linköping, December 2019 Christian Busse iii The nature of science is not that of a steady, linear progression toward the truth, but rather a tortuous road, often characterized by dead ends and U-turns, and yet ultimately inching toward a better, if tentative, understanding of the natural world.

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Section: Characteristic Fracture Behaviour Of Single-crystalsmentioning

confidence: 60%

Modelling of Crack Growth in Single-Crystal Nickel-Base Superalloys

Busse

2019

Linköping Studies in Science and Technology. Dissertations

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“…Furthermore, Mode I FCGRs are presented for the sake of comparison. The Mode I FCGRs are based on the evaluations of the performed experiments in this study, and on a different specimen geometry [22].…”

Section: Previous Research Concerning Crystallographic Fcgrs Has Been Restrictedmentioning

confidence: 99%

Evaluation of the crystallographic fatigue crack growth rate in a single-crystal nickel-base superalloy

Busse

Palmert

Sjödin

et al. 2019

International Journal of Fatigue

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Cracks in single-crystal nickel-base superalloys have been observed to switch cracking mode from Mode I to crystallographic cracking. The crack propagation rate is usually higher on the crystallographic planes compared to Mode I, which is important to account for in crack growth life predictions. In this paper, a method to evaluate the crystallographic fatigue crack growth rate, based on a previously developed crystallographic crack driving force parameter, is presented. The crystallographic crack growth rate was determined by evaluating heat tints on the fracture surfaces of the test specimens from the experiments.Complicated crack geometries including multiple crystallographic crack fronts were modelled in a three dimensional finite element context. The data points of the crystallographic fatigue crack growth rate collapse on a narrow scatter band for the crystallographic cracks indicating a correlation with the previously developed crystallographic crack driving force.

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“…During 100°C isothermal testing or OP-TMF, where the maximum stress is reached at low temperature, there is a possibility for crystallographic crack growth in the single crystal alloy studied 27 . In the present testing, the aim was to generate data for Mode I crack growth and care has therefore been taken to avoid crystallographic crack growth, which is known to occur along the {111} planes 27 . Crystallographic crack growth was avoided by pre-cracking the specimens isothermally at 750°C or 850°C.…”

Section: Crystallographic Crack Growthmentioning

confidence: 99%

“…Under some conditions, crystallographic crack growth occurs along the {111} planes, even if these are far from perpendicular to the loading direction. For the specific single crystal alloy which is the focus of the present work, the crystallographic crack growth behaviour has been previously characterized and discussed in relation to findings for similar alloys 27 . In this previous work, the crack growth behaviour was studied under isothermal fatigue conditions in order to allow the usage of traditional, relatively simple testing procedures.…”

Section: Introductionmentioning

confidence: 99%

Thermomechanical fatigue crack growth in a single crystal nickel base superalloy

Palmert

Gustafsson

2019

International Journal of Fatigue

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Thermomechanical fatigue crack growth in a single crystal nickel base superalloy was studied. Tests were performed on single edge notched specimens, using in phase and out of phase thermomechanical fatigue cycling with temperature ranges of 100-750°C and 100-850°C and hold times at maximum temperature ranging from 10s to 6h. Isothermal testing at 100°C, 750°C and 850°C was also performed using the same test setup. A compliancebased method is proposed to experimentally evaluate the crack opening stress and thereby estimate the effective stress intensity factor range ΔKeff for both isothermal and nonisothermal conditions. For in phase thermomechanical fatigue, the crack growth rate is increased if a hold time is applied at the maximum temperature. By using the compliance-based crack opening evaluation, this increase in crack growth rate was explained by an increase in the effective stress intensity factor range which accelerated the cycle dependent crack growth. No significant difference in crack growth rate vs ΔKeff was observed between in phase thermomechanical fatigue tests and isothermal tests at the maximum temperature. For out of phase thermomechanical fatigue, the crack growth rate was insensitive to the maximum temperature and also to the length of hold time at maximum temperature. The crack growth rate vs ΔKeff during out of phase thermomechanical fatigue was significantly higher than during isothermal fatigue at the minimum temperature, even though the advancement of the crack presumably occurs at the same temperature.Dissolution of γ′ precipitates and recrystallization at the crack tip during out of phase thermomechanical fatigue is suggested as a likely explanation for this difference in crack growth rate.

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Fatigue crack growth behaviour of an alternative single crystal nickel base superalloy

Cited by 30 publications

References 32 publications

Modelling of Crack Growth in Single-Crystal Nickel-Base Superalloys

Modelling of Crack Growth in Single-Crystal Nickel-Base Superalloys

Evaluation of the crystallographic fatigue crack growth rate in a single-crystal nickel-base superalloy

Thermomechanical fatigue crack growth in a single crystal nickel base superalloy

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