Modelling of TMF Crack Initiation in Smooth Single-Crystal Superalloy Specimens

Leidermark, Daniel; Segersäll, Mikael; Moverare, Johan; Simonsson, Kjell

doi:10.4028/www.scientific.net/amr.891-892.1283

Cited by 2 publications

References 8 publications

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Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy

Segersäll

Leidermark

Moverare

2015

Materials Science and Engineering: A

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In this study, the influuence from crystal orientation on the thermomehanical fatigue (TMF) behaviour of the recently developed single-rystal superalloy STAL-15 is considered, both from an experimental and a nite element (FE) perspective. Experimental results show that there is a strong inuence from the elastic stiffness, with respect to the loading direction, on the TMF life. However, the results also indicate that the number of active slip planes duringdeformation inuence the TMF life, where specimens with a higher number of active slip planes are favoured compared to specimens with fewer active slip planes. The higher number of active slip planes results in a more widespread deformation compared to a more conentrated deformation when only one slip plane is active. Deformation bands with smeared and elongated γ-precipitates together with deformation twinning were found to be major deformation mechanisms, where the twins primarily were observed in specimens with several active slip planes. From an FE-perspective, therystal orientation with respect to the loading direction is quantied and adopted into a framework which makes it possible to describe the internal crystallographic arrangement and its entities in a material model. Further, a material model which incorporates the crystalorientation is able to predict the number of slip planes observed from microstructural observations, as well as the elasticstiness of the material with respect to the loading direction.

On the day of the defence day the status of this article was Manuscript.

The work has been financially supported by Siemens Industrial Turbomachinery AB in Finspang, Sweden, and the Swedish Energy Agency, via the Research Consortium of Materials Technology for Thermal Energy Processes, Grant no. KME-702. In addition, the support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU #2009-00971) is also acknowledged.

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Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy

Segersäll

Leidermark

Moverare

2015

Materials Science and Engineering: A

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On the day of the defence day the status of this article was Manuscript.

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Comparative Analysis of Stress Relaxation and Creep in a Single-Crystal Superalloy

Leidermark

Moverare

2016

Volume 7A: Structures and Dynamics

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The creep response of the single-crystal nickel-base superalloy MD2 has been investigated in this study. A set of constant load creep experiments was performed loaded in the nominal [001], [011] and [111] crystal orientations. A crystal plasticity - creep relaxation model, based on thermomechanical fatigue stress relaxation tests, was benchmarked to simulate the creep behaviour. The responses from the model were then compared to the results obtained during the creep tests. From the comparison it could observed that a trend for the [001] crystal orientation is present. A relative creep response between the simulations and experiments could be observed for the different stress levels. At high and increasing stress levels the relative relation is increasing. Under a certain stress level the relative relation is instead increasing for decreasing stress levels. This relative relation arises from the stress relaxation evaluation process, in which the creep parameters are defined, presumably due to the high stress relaxation that is present in the initial time frame. No trend was seen for the [011] and [111] crystal orientations. A discrepancy between the simulations and experiments was still obtained, also related to the high stress relaxation of the initial time frame.

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Modelling of TMF Crack Initiation in Smooth Single-Crystal Superalloy Specimens

Cited by 2 publications

References 8 publications

Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy

Influence of crystal orientation on the thermomechanical fatigue behaviour in a single-crystal superalloy

Comparative Analysis of Stress Relaxation and Creep in a Single-Crystal Superalloy

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