Thermodynamic, kinetic and phase transformation calculations in the field of single crystal nickel based superalloys

Transcription

1 Thermodynamic, kinetic and phase transformation calculations in the field of single crystal nickel based superalloys R. Rettig, M.M. Franke, R.F. Singer Institute of Science and Technology of Metals (WTM) Department of Materials Science and Engineering University of Erlangen-Nürnberg Germany ThermoCalc User Meeting - Aachen 5 th September 2013 Folie 1

2 Agenda o Nickel-based alloys as a key for energy production o Thermodynamic and kinetic databases for alloy development o Heat treatment modelling o Simulation of microstructure evolution o Summary Folie 2

3 Combined cycle power plant Siemens AG Efficiency (2007): ca. 58% (330 g CO 2 / kwh) Aim 2020: ca. 63% (300 g CO 2 / kwh) 1st stage blade 250 mm, 4,3 kg 1 MW 50 Hz 10 t 1000 C 3 yrs ,- $ Siemens AG plant control condensor generator steam turbine gas turbine heat recovery steam generator Keppel, Alstom, Cooretec Workshop, 2006 Folie 3

4 efficiency / % Carnot-efficiency / % efficiency increase Efficiency of fossile power plants Development of efficiency Relation of efficiency and process temperature gas (CC) brown coal plans year of entry into service turbine outlet temperature is 500 C material improvement process temperature / C data according to Siemens AG and DPG (2005) efficiency increase is always related to higher material temperatures Folie 4

5 Service temperature Development of nickel-based superalloys single crystalline temperature capability of nickelbased superalloys directionally solidified polycrystalline wrought alloys Year of development Harada et al. (2003) IGTC2003 Folie 5

6 Turbine blades T m T g T c 1 st stage, SGT5-4000F, Siemens AG polycrystalline directionally solidified single crystalline Folie 6

7 Turbine blades T m T g 1 mm T c 1 st stage, SGT5-4000F, Siemens AG polycrystalline directionally solidified single crystalline Folie 7

8 content / wt-% Single crystal nickel-based superalloys g g Rhenium Ruthenium René N5 CMSX-10 CMSX-4 René N6 5 µm 4 PWA René N2 CMSX-2 0 1st 2nd 3rd 4th 5th generation composition of single crystal superalloys γ + γ -microstructure gives unique creep properties typical alloying elements (ca. 8 10): Ni-Al-Co-Cr-Mo-Re-Ru-Ta-Ti-W-B-Zr-Y Folie 8

9 Material / process simulation at Institute WTM thermodynamics ThermoCalc diffusion DICTRA phase transformations TC-PRISMA process simulation (temperature-, fluid flow) - Flow3D - ProCAST - inhouse Lattice Boltzmann code Institute WTM / NMF microstructure MICRESS mechanics (finite elements) ABAQUS computer-aided alloy development inhouse software (MultOPT) Folie 9

10 Agenda o Nickel-based alloys as a key for energy production o Thermodynamic and kinetic databases for alloy development o Heat treatment modelling o Simulation of microstructure evolution o Summary Folie 10

11 phase fractions / mol-% Fields of application CMSX-4, database TTNi8 o o prediction of: liquidus (melting) temperature γ -phase fraction γ -solvus temperature TCP-phase solvus temperatures limitations: exotic alloying elements are not available g g' L P temperature / C most commercial databases are not changable and the exact parameters are often not accessible calculations for untypical compositions may be critical calculations are only valid for stable equilibrium Folie 11

12 melting temp. meas. / C g' solvus meas. / C Verification of commercial database TTNi7 liquidus g -solvus no Re and Ru with Re 1450 with Ru 1400 no Re and Ru with Re with Ru Shao05 Fuchs02 Sponseller96 Copland01 Dharwadkar92 this work melting temp. sim. / C Shao05 Fuchs02 Sponseller96 Copland01 Dharwadkar92 this work Caron g' solvus sim. / C R. Rettig et al. Defect and Diffusion Forum (2009) Folie 12

13 composition g' / at-% composition g' / at-% composition g / at-% composition g / at-% Phase compositions calculated with TTNi7 Cr 10 Co Al 10 Mo Ru 1 Ti Ta 1 Re 0,1 0, temperature / C Al 10 Ti Co Cr 1 0, temperature / C good agreement temperature / C 10 Ru 1 Ta Mo Re 0, temperature / C bad agreement R. Rettig et al. Defect and Diffusion Forum (2009) Folie 13

14 diffusion coefficient D / m²s Diffusion database development for Ni-Ge NiGe8 NiGe1 R. Rettig et al. Journal of Phase Equilibria and Diffusion 32 (2011) PWA1483 René N5 diffusion coefficient D Ge / m²s -1 diffusion coefficient D / m²s x x x x10-4 1/T / 1/K interdiffusion Ge impurity self diffusion Rettig et al. (2011) C 1200 C Hirano et al. (1962) Mantl et al. (1983) C 6.5x x x x10-4 1/T / 1/K impurity diffusion Ge / at-% DICTRA-database from diffusion couple measurements Folie 14

15 Agenda o Nickel-based alloys as a key for energy production o Thermodynamic and kinetic databases for alloy development o Heat treatment modelling o Simulation of microstructure evolution o Summary Folie 15

16 Agenda o Nickel-based alloys as a key for energy production othermodynamic and kinetic databases for alloy development o Heat treatment modelling o Simulation of microstructure evolution o Summary Folie 16

17 A multicomponent, multiphase precipitation model Idea of model Loop for all timesteps Loop for all precipitate types Driving force from CALPHAD Nucleation rate New nucleation Growth of all existing particles Loop for all particles Growth rate using CALPHAD timestep 1 Total removal of solute from matrix Volume change Solute removal from matrix numerical Kampmann-Wagner model (1984), T. Sourmail (2002) red: new multicomponent model Folie 17

18 A multicomponent, multiphase precipitation model Idea of model Loop for all timesteps Loop for all precipitate types Driving force from CALPHAD Nucleation rate New nucleation Growth of all existing particles Loop for all particles Growth rate using CALPHAD timestep 1 timestep 2 Total removal of solute from matrix Volume change Solute removal from matrix numerical Kampmann-Wagner model (1984), T. Sourmail (2002) red: new multicomponent model Folie 18

19 A multicomponent, multiphase precipitation model Idea of model Loop for all timesteps Driving force from CALPHAD Loop for all precipitate types Nucleation rate timestep 1 timestep 2 timestep 3 New nucleation Growth of all existing particles Total removal of solute from matrix Loop for all particles Growth rate using CALPHAD Volume change Solute removal from matrix numerical Kampmann-Wagner model (1984), T. Sourmail (2002) red: new multicomponent model Folie 19

20 temperature / C Modelling of TCP-phase precipitation FIB-tomography multicomponent Kampmann-Wagnermodel (coupled to ThermoCalc and DICTRA) databases: TTNi8 + MobNi % Ru 2.5 % Ru 9 x 7 x 6 μm 3 experimental 3 rd generation alloy ASTRA1-20 K. Matuszewski, R. Rettig et al. Advanced Engineering Materials (2013) vol-% P time / h experimental data: Sato et al. (2006) Scripta Mat Folie 20

21 precipitate length / µm Modelling of TCP-phase precipitation Driving force influences precipitate length precipitate length EROS4 IN792Re experiment [Vol06] simulation driving force / kj mol -1 driving force for precipitation C EROS4 IN792Re equilibrium 10 5 time / h Rettig et al. Acta Materialia 59 (2011) temperature / C the large difference in the driving force in both alloys is the reason for the very different precipitate lengths Folie 21

22 Agenda o Nickel-based alloys as a key for energy production o Thermodynamic and kinetic databases for alloy development o Heat treatment modelling o Simulation of microstructure evolution o Summary Folie 22

23 Summary Fields of application of thermodynamic and kinetic simulations Advanced modelling using CALPHAD-calculations as a basis Heat treatment simulation Precipitation simulation Folie 23