April 20, 2023 1

Microstructure of creep-exposed single crystal nickel base superalloy CSMX4

This research project has been supported by the European Commission under the 6th Framework Programme through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract n°: RII3-CT-2003-505925 (NMI3).

1 Nuclear Physics Institute Řež near Prague, Czech Republic (email:strunz@ujf.cas.cz)2 Research Center Řež, CZ-25068 Řež near Prague, Czech Republic3 Technical University of Košice, Dept. of Materials Science, Slovakia4 Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87,

12205 Berlin, Germany5 Technical University Berlin,10623 Berlin, Germany6 Laboratory for Neutron Scattering, PSI & ETH Zürich, CH-5232 Villigen, Switzerland

P. Strunz1,2, J. Zrník3, A. Epishin4, T. Link5, S. Balog6

April 20, 2023 2

1 Nuclear Physics Institute Řež near Prague, Czech Republic (email:strunz@ujf.cas.cz)

2 Research Center Řež, CZ-25068 Řež near Prague, Czech Republic3 Technical University of Košice, Dept. of Materials Science, Slovakia4 Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87,

12205 Berlin, Germany5 Technical University Berlin,10623 Berlin, Germany6 Laboratory for Neutron Scattering, PSI & ETH Zürich, CH-5232 Villigen,

Switzerland

P. Strunz1,2, J. Zrník3, A. Epishin4, T. Link5, S. Balog6

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Microstructure of creep-exposed single

crystal nickel base superalloy CSMX4

This research project has been supported by the European Commission under the 6th Framework Programme through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract n°: RII3-CT-2003-505925 (NMI3).

April 20, 2023 4

Components in gas turbines fabricated of Ni base superalloys operate under complex creep and fatigue conditions.

Main structural changes during exposure: morphology change - rafting of γ’ precipitates in γ matrix.

Residual lifetime estimation: need to evaluate reliably the progress of γ’ degradation in dependence on exposure …

… and relate these changes to the magnitude of stress

Information can be obtained form the analysis of geometrical parameters of the γ’ microstructure and γ/ γ’ misfit [1,2].

Bulk sensitive SANS: detection of morphological changes in γ’ phase due to the operation condition [3].

Components in gas turbines fabricated of Ni base superalloys operate under complex creep and fatigue conditions.

Main structural changes during exposure: morphology change - rafting of γ’ precipitates in γ matrix.

Residual lifetime estimation: need to evaluate reliably the progress of γ’ degradation in dependence on exposure …

… and relate these changes to the magnitude of stress

Information can be obtained form the analysis of geometrical parameters of the γ’ microstructure and γ/ γ’ misfit [1,2].

Bulk sensitive SANS: detection of morphological changes in γ’ phase due to the operation condition [3].

Ni-superalloys - raftingNi-superalloys - rafting

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CMSX4 single crystal samples

SANS study (PSI Villigen, SANS-II) of γ’-morphology

continuous change of applied stress ensured by preparing the creep sample in the form of a cone

Relation of microstructural changes to the applied stress

CMSX4 single crystal samples

SANS study (PSI Villigen, SANS-II) of γ’-morphology

continuous change of applied stress ensured by preparing the creep sample in the form of a cone

Relation of microstructural changes to the applied stress

ExperimentalExperimental

Aim of the SANS experimentAim of the SANS experiment

to evaluate the morphological changes of γ’ in creep exposed CMSX4 samples and relate them to the applied stress

to test a novel, cost effective method of preparation of sample material exposed to various stress levels

to evaluate the morphological changes of γ’ in creep exposed CMSX4 samples and relate them to the applied stress

to test a novel, cost effective method of preparation of sample material exposed to various stress levels

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Conic CMSX4, spatial scan

SANS-II, SINQ, PSI Villigen, CH

SANS-II, SINQ, PSI Villigen, CH

• optimum 2D fit and sections through the 3D model

• Assumption: volume fraction constant ( <= the same temperature at all locations)

• optimum 2D fit and sections through the 3D model

• Assumption: volume fraction constant ( <= the same temperature at all locations)

oriented (ω-scan, tilt): <100> parallel to the beam<001> nearly vertical

oriented (ω-scan, tilt): <100> parallel to the beam<001> nearly vertical

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SEM - γ’ morphology changes SEM - γ’ morphology changes

Advanced rafting

Advanced rafting

Small diameter end Small diameter end centre centre Large diameter end Large diameter end

for the lowest stress, still partially unrafted

for the lowest stress, still partially unrafted

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Stress along the sample axisStress along the sample axis

CMSX4

T=1100°C

t=100h

σmin=35MPa

σmax=135MPa

CMSX4

T=1100°C

t=100h

σmin=35MPa

σmax=135MPa

April 20, 2023 9

precipitate size and distance, specific surface

• Even for lowest stress: advanced rafting

• Evolution of rafts with stress level clearly observable from the parameters obtained from SANS curves

• Even for lowest stress: advanced rafting

• Evolution of rafts with stress level clearly observable from the parameters obtained from SANS curves

SANS results

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A different extent of γ'-precipitates rafting was observed for variously exposed positions inside the sample

The tendency corresponds to the expected evolution: the larger stress, the more advanced rafting process.

Qualitatively, the 2D scattering curves confirmed the results of the electron microscopy performed on the samples from the same bar

The detailed evaluation of the data brought a series of morphological parameters in dependence on the applied stress.

The use of conic sample and spatial scan facilitates determination of microstructure evolution in dependence on exposure parameters

A different extent of γ'-precipitates rafting was observed for variously exposed positions inside the sample

The tendency corresponds to the expected evolution: the larger stress, the more advanced rafting process.

Qualitatively, the 2D scattering curves confirmed the results of the electron microscopy performed on the samples from the same bar

The detailed evaluation of the data brought a series of morphological parameters in dependence on the applied stress.

The use of conic sample and spatial scan facilitates determination of microstructure evolution in dependence on exposure parameters

SummarySummary

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[1] H. Mughrabi, H. Biermann, T. Ungar: Superalloys 1992, TMS, Warrendale, PA, 599

[2] T. Link, A. Epishin, U. Brickner, P.D. Portella: Acta Mater. 8, 2000, 1981.

[3] J. Zrnik, P. Strunz, P. Hornak, V. Vrchovinsky, A. Wiedenmann: Applied Physics A 74,(2002] 1155.

[4] D.K. Morris, J.B. Wahl: Proc. of 4th Int. Conf. Advanced materials for 21st Century Turbines and Power Plants, Eds. A. Strange et all, 2000, 832.

[1] H. Mughrabi, H. Biermann, T. Ungar: Superalloys 1992, TMS, Warrendale, PA, 599

[2] T. Link, A. Epishin, U. Brickner, P.D. Portella: Acta Mater. 8, 2000, 1981.

[3] J. Zrnik, P. Strunz, P. Hornak, V. Vrchovinsky, A. Wiedenmann: Applied Physics A 74,(2002] 1155.

[4] D.K. Morris, J.B. Wahl: Proc. of 4th Int. Conf. Advanced materials for 21st Century Turbines and Power Plants, Eds. A. Strange et all, 2000, 832.

ReferencesReferences