October 28, 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 (NMI3). 1 Nuclear Physics Institute Řež near Prague, Czech Republic 2 Research Center Řež, CZ Řež near Prague, Czech Republic 3 Technical University of Košice, Dept. of Materials Science, Slovakia 4 Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, Berlin, Germany 5 Technical University Berlin,10623 Berlin, Germany 6 Laboratory for Neutron Scattering, PSI & ETH Zürich, CH-5232 Villigen, Switzerland P. Strunz 1,2, J. Zrn í k 3, A. Epishin 4, T. Link 5, S. Balog 6

October 28, Nuclear Physics Institute Řež near Prague, Czech Republic 2 Research Center Řež, CZ Řež near Prague, Czech Republic 3 Technical University of Košice, Dept. of Materials Science, Slovakia 4 Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, Berlin, Germany 5 Technical University Berlin,10623 Berlin, Germany 6 Laboratory for Neutron Scattering, PSI & ETH Zürich, CH-5232 Villigen, Switzerland P. Strunz 1,2, J. Zrn í k 3, A. Epishin 4, T. Link 5, S. Balog 6

October 28, 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 (NMI3).

October 28,  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 - rafting

October 28,  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 Experimental Aim 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

October 28, Conic CMSX4, spatial scan 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): parallel to the beam nearly vertical oriented (ω-scan, tilt): parallel to the beam nearly vertical

October 28, SEM - γ’ morphology changes  Advanced rafting  Small diameter end  centre  Large diameter end  for the lowest stress, still partially unrafted

October 28, Stress along the sample axis  CMSX4  T=1100°C  t=100h  σ min =35MPa  σ max =135MPa  CMSX4  T=1100°C  t=100h  σ min =35MPa  σ max =135MPa

October 28, 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

October 28,  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 Summary

October 28, [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, [3] J. Zrnik, P. Strunz, P. Hornak, V. Vrchovinsky, A. Wiedenmann: Applied Physics A 74,(2002] [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, [3] J. Zrnik, P. Strunz, P. Hornak, V. Vrchovinsky, A. Wiedenmann: Applied Physics A 74,(2002] [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. References