2013-09-05, Dr.-Ing. B. Laux - RWTH Aachen...

Confidential © Siemens AG 2013 All rights reserved. http://siemens.com/energy/power-generation/gas-turbines

Technology Classification: ECCN: AL: US-Content: Yes or NoThis document is subject to the U.S., Canadian, EU/German and/or other national export regulations. Diversion contrary to National law may be prohibited.

DICTRA Modeling of TLP Bonding Processes for Ni-based Superalloys

2013-09-05, Dr.-Ing. B. Laux

Thermo-Calc Users‘ Meeting

September 05/06 2013ACCESS e.V. Materials and Processes

Confidential © Siemens AG 2013 All rights reserved.

Technology Classification: ECCN: EAR99 AL: N US-Content: NoThis document is subject to US Export Administration Regulations, EU Dual-Use Regulations, and or other foreign national export regulations. Diversion contrary to law is prohibited."

Table of Contents

Outline

Introduction: Diffusion Bonding

Brazing Experiments

Modeling

Summary and Next Steps

B. Laux / E F PR GT EN MT 2 4




• Joining technology for the repair of gas turbine components (Ni-/Co-based high temperature materials)

• Filling of cracks, build-up brazing, coupon repairs

• Idea: Filler material similar to base material + melting point depressant (MPD)

• MPD diffuses into base material during isothermal hold time

• Diffusion controlled isothermal solidification

• If hold time is long enough to provide for complete isothermal solidification, mechanical properties of braze joints are on base material level

• Epitaxial healing of SX material can be achieved





• Material System• Braze alloy including MPD• Base material matrix

• Geometry• Width of braze gap• Bonding pressure

• Brazing temperature• Isothermal hold time• Heat treatment after brazing

Process Parameters Effect

• Braze gap widening, solubility of MPD

• Microstructure braze gap and base material

• Precipitates• Grain size and orientation• Element distribution• Morphology

• Existence and width of centerline eutectic


Mechanical properties of braze joint



Brazing Experiments: Material System

Ni Cr Co W Ta Al Hf Si B C

MBF 80 bal. 15.2 - - - - - - 4.0 0.06

MBF 50 bal. 19.0 - - - - - 7.3 1.5 0.08

Ni-Flex 110* bal. 10.0 5.0 4.0 4.0 2.0 - - 1.5 -

Ni-Flex 115* bal. 9.0 8.0 4.0 4.0 2.0 1.0 - 3.0 -

Braze Alloys (Foils, 50 m)

Base Material

Ni Cr Co W Mo Ta Al Ti B C Hf Zr

Alloy 247 CC/DS

bal. 8.1 9.2 9.5 0.5 3.2 5.6 0.7 0.01 0.07 1.4 0.01

René 80 bal. 14 9.5 4.0 4.0 - 3.0 4.8 0.015 0.17 - 0.03

* Ni-Flex foils not homogeneous, boron-free core, boron-containing boundary




Brazing Experiments: Set-up

Temperature Time

Cycle 1 1204°C 0.5h

Cycle 2 1204°C 1h

Cycle 3 1204°C 2h

Cycle 4 1204°C 0.5h + post- braze heat treatment

Cycle 5 1232°C 2h

Cycle 6 1243°C 4h

Brazing Cycle




Brazing Experiments: Metallographic Evaluation

Cycle 3 (2h @ 1204°C)

René 80

Ni Flex 110 Ni Flex 115

Alloy 247 CC

MBF 50 MBF 80

Alloy 247 DS





Cycle 4 (0.5h @ 1204°C + heat treatment)

René 80


Alloy 247 CC

MBF 50 MBF 80

Alloy 247 DS





Cycle 5 (2h @1232°C)

Alloy 247 CC

Ni Flex 110

Alloy 247 DS

MBF 80 Ni Flex 110 MBF 80

Cycle 6 (4h @ 1243°C)

Precipitation of secondary phases and incipient melting




NiFlex 110

MBF 50 MBF 80

NiFlex 115

Modeling: Thermo-Calc – Calculation of braze alloys

TS TS TL

TS TSTL




Modeling: DICTRA – Moving Boundary Model

• Simulation as Moving Boundary Model

• Variation of gap width and temperature

• Symmetrical geometry: Modeling of half gap width and base material (2 regions)

• Base material: pure Ni-matrix, René 80, Alloy 247

• Braze gap: MBF 50, MBF 80, NiFlex 110, NiFlex 115

• In-situ boride formation cannot be included in DICTRA 26

Prediction of isothermal solidification time

Base MaterialBraze Gap

0.5 W0 20 mmt = t1 (Widening)

t = t2 (Isothermal Solidification)

Braze Gap

Base Material

Base Material

t = t0




Modeling: Set up in DICTRA 26 (Moving Boundary Model)


go datsw ttni7def-spec ni cr mo w co al brej ph *rest ph fcc_a1 liquidgetappend mobni1@@Elementsdef-sys ni cr mo w co al brej ph *rest ph fcc_a1 liquid get@@DICTRAgo d-m@@Simulation Temperatureset-con GLOBAL T 0 1477.15; * N@@Geometryent-geo 0@@Regionsent-reglotent-regbaselotYES@@Grid Braze Gapent-gridlot25e-6geo500.97

@@Grid Base Materialent-gridbase20e-4geo1001.03@@Liquid Phase in Braze Gapent-phACTIVElotMATRIXLIQUID@@FCC in Base Materialent-phACTIVEbaseMATRIXfcc@@Compositions@@Braze Gap (MBF 80) Liquident-complotLIQUIDniw-pCr LINEAR 15.2 15.2Co LINEAR 1e-5 1e-5Mo LINEAR 1e-5 1e-5W LINEAR 1e-5 1e-5Al LINEAR 1e-5 1e-5B LINEAR 4 4

@@Base Material FCCent-compbaseFCC_A1niw-pCr LINEAR 14 14Co LINEAR 9.5 9.5Mo LINEAR 4 4W LINEAR 4 4Al LINEAR 3 3B LINEAR 0.015 0.015@@Simulation Times-sim-time100000 y 200 1E-10 1E-15@@Simulation Conditions (Euler

backwards)s-s-c0 1 2 NO ACTIVITIES YES 99 1 2 NO YES NOsave R80_MBF80_1204_50mu.dic @@Start Simulationsim




• In-situ boride formation not included

• René 80 + MBF 80:

• Max. gap width: 2 x 34.5m

• Isothermal solidification finished after about 18.7h

• Alloy 247 + MBF 80:

• Max. gap width: 2 x 33m


René 80, MBF 80, 1204°C, W0 = 50 µm, Ti excluded

Modeling: DICTRA 26 – Moving Boundary Model

Alloy 247, MBF 80, 1204°C, W0 = 50 µm, Ti, Hf excluded


End of solidification

Max. gap width


Max. gap width






• In-situ boride formation not included

• René 80 + NiFlex 110:



• Alloy 247 + NiFlex 110:



René 80, NiFlex110, 1204°C, W0 = 50 µm, Ti excluded

Alloy 247, NiFlex110, 1204°C, W0 = 50 µm, Ti, Hf excluded






Complete isothermal solidification only predicted for René 80 + NiFlex 110


1h 2h 5h

T=1204°C



Comparison to Brazing Experiments

Cycle 3 (1204°C, 2h)

René 80


Alloy 247 CC

MBF 50 MBF 80

Alloy 247 DS


Iso. Sol. completed

Iso. Sol. completed




Modeling: DICTRA 26 – Homogenization Model

Composition Elements excluded Phases

René 80 Ni-14Cr-9.5Co-4Mo-4W- 3Al-0.15B

Ti, C, Zr FCC + M3B2_TETR (Mo- and Cr-rich boride)

Alloy 247 Ni-8.1Cr-9.2Co-0.5Mo- 9.5W-3.2Ta-5.6Al-0.01B

Mo, Ti, C, Zr, Hf FCC + M3B2_TETR (W- and Cr-rich boride)

MBF 80 Ni-15.2Cr-4B C LIQUID

NiFlex110 Ni-10Cr-5Co-4W-4Ta-2Al- 1.5B

LIQUID + FCC

Stable Phases at 1204°C (TC, Database TTNi7)




go datsw ttni7def-spec ni cr mo w co al brej ph *rest ph fcc_a1 liquid m3b2_tetr getappend mobni1@@Elementsdef-sys ni cr mo w co al brej ph *rest ph fcc_a1 liquid m3b2_tetr get@@DICTRAgo d-m@@Simulation Temperatureset-con GLOBAL T 0 1477.15; * N@@Geometryent-geo 0@@Regionsent-regsystem@@Grid ent-gridsystem1e-3geo1001.05

@@ Phases Present@@ Rene 80ent-phaseactivesystemmatrixfcc@@ liquid spheroidenter-phaseactivesystemsphliqenter-phaseactivesystemsphmb_orthenter-phaseactivesystemsphm3b2_tetr@@ Composition of Phases@@ FCC Phaseenter-compsystemfccniw_pcr func 15.2 - 1.2*HS(x-25e-6);co func 1e-5 + 9.5*HS(x-25e-6);al func 1e-5 + 3*HS(x-25e-6);

mo func 1e-5 + 4*HS(x-25e-6);b func 4 - 3.985*HS(x-25e-6);w func 1e-5 + 4*HS(x-25e-6);@@ LIQUID composition according to

equilibriumenter-compsystemliqyes@@ M3B2_TETR composition according

to equilibriumenter-compsystemm3b2_tetryes@@ Simulation timeset-sim-time 7200yes100 1e-10 1e-15@@Simulation Conditionss-s-c 0 1 2 NO ACTIVITIES YES 99 1 2 NO

YES NO@@ Application of homogenization modelHomo yes n n y 1000 y n log n n n@@ Hom. Func. (Hashin Shtrikman:

Majority phase as matrix with excluded phases)

en-ho 12 m3b2_tetr nSaveR80_MBF80_1204_50mu_M3B2_hom.dic @@Start Simulationsim

Modeling: Set up in DICTRA 26 (Homogenization Model)




Modeling: DICTRA 26 – Homogenization Model

Alloy 247, Ni-Flex 110, 2h @ 1204°C, W0 = 50 µm, Ti excluded

René 80, MBF 80, 2h @ 1204°C, W0 = 50 µm, Ti excluded

0.1s

520s

1s1s

1000s

3600s

100s

7200s

1s

10s

100s

510s

1s1000s

3600s

100s

7200s

• Simulation as Homogenization Model

• MBF 80: completely liquid at 1204°C

• Ni-Flex 110: not completely liquid

• Position of phase interface cannot be plotted

• René 80 + MBF 80:

• Isothermal solidification finished after about 520s

• Alloy 247 + NiFlex 110:

• Isothermal solidification finished after about 510s

• In-situ boride formation (M3 B2 ) included → Predicted time for isothermal solidification extremely short




go datsw ttni7def-spec ni cr mo w co al brej ph *rest ph fcc_a1 liquid m3b2_tetr getappend mobni1@@Elementsdef-sys ni cr mo w co al brej ph *rest ph fcc_a1 liquid m3b2_tetr get@@DICTRAgo d-m@@Simulation Temperatureset-con GLOBAL T 0 1477.15; * N@@Geometryent-geo 0@@Regionsent-reglotent-regbaselotYES@@Grid Braze Gapent-gridlot25e-6geo300.97

@@Grid Base Materialent-gridbase20e-4geo1001.03@@Liquid Phase in Braze Gapent-phACTIVElotMATRIXLIQUID@@FCC in Base Materialent-phACTIVEbaseMATRIXfcc@@M3B2 in Base Materialent-phACTIVEbasesphm3b2_tetr@@Compositions@@Braze Gap (MBF 80) Liquident-complotLIQUIDniw-p

Cr LINEAR 15.2 15.2Co LINEAR 1e-5 1e-5Mo LINEAR 1e-5 1e-5W LINEAR 1e-5 1e-5Al LINEAR 1e-5 1e-5B LINEAR 4 4@@Base Material FCCent-compbaseFCC_A1niw-pCr LINEAR 14 14Co LINEAR 9.5 9.5Mo LINEAR 4 4W LINEAR 4 4Al LINEAR 3 3B LINEAR 0.015 0.015@@Base Material M3B2ent-compbasem3b2_tetry@@Simulation Times-sim-time3600 y 50 1E-10 1E-15@@Simulation Conditionss-s-c 0 1 2 NO ACTIVITIES YES 99

1 2 NO YES NOSaveR80_MBF80_1204_50mu_M3B2.dic @@Start Simulationsim

Modeling: Set up in DICTRA 27



Modeling: DICTRA 27


• Simulation as Homogenization Model

• Position of phase interface can be tracked in homogenization model

• Combination of boride formation with two regions set-up

• Phases included: FCC (matrix), LIQUID (braze gap), M3 B2 in base material

→ Predicted time for isothermal solidification still very short

René 80, MBF 80, 1204°C, W0 = 50 µm, Ti excluded

Max. gap width

100s

1000s

Plot of position of interface not complete

Phase boundary

1s1s

100s

1000s3600s

3600s



Summary

• Modeling of TLP bonding of Ni-base superalloys challengingMany elements to be includedResults fit qualitatively to experimental resultsCalculated times w/o boride formation are relatively long Implementation of borides lead to extremely short solidification timesPrediction of exact isothermal solidification time is difficult





Next Steps

• Identification of borides within Alloy 247 (EBSD, XRD)• Implementation of these boride types in DICTRA models • Modeling of complete brazing cycle 4 (brazing + post-braze heat treatment)Comparison to experimental findings (solidification completed for René 80 + MBF 80)

• Modeling of complete brazing cycle 5, 6 (1232°C, 1243°C)Comparison to experimental findings (incipient melting)

• Inclusion of more elements• Set-up of NiFlex110 as non-homogeneous foil (boron-free core)

Optimization of current brazing cycles





Contact

Dr.-Ing. Britta Laux Joining and Repair Siemens AG Energy Sector E F PR GT EN MT 2 4

Huttenstr. 12 10553 Berlin

Phone: +49 (30) 3461-11989 Fax: +49 (30) 3461-2153

E-mail: [email protected]


2013-09-05, Dr.-Ing. B. Laux - RWTH Aachen...

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