lÖt 2013 aachen (2013-06-20) – dr. s. piegert , i...

Unrestricted © Siemens AG 2013 All rights reserved. http://siemens.com/energy/power-generation/gas-turbines Technology Classification: ECCN: EAR99 AL: N US-Content: 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.

E F PR GT EN MT 2 4

Characterisation and Optimisation of Braze Joints – Simulation and Experiment

LÖT 2013 Aachen (2013-06-20) – Dr. S. Piegert, I. Reinkensmeier

Unrestricted © 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."

Piegert / E F PR GT EN MT 2 42013-06-20

Motivation

Combustion Chamber

24 Hybrid Burners

Results of former attempt• heat treatment cycle

• 1100 °C/10 min + 1000 °C/4 h• static properties

• Ni 610 Rm = 310 MPa• Ni 620 Rm = 285 MPa• Ni 650 Rm = 230 MPa

• thermocyclic tests: failure after 12 cycles (RT – 400 °C)

cracked joint



Outline

• introduction

• boundary conditions

• diffusion brazing

• methods

• simulation and experiment

• design of experiment

• process robustness

• diffusion profiles

• conclusions

Page 3



Boundary Conditions• temperatures up to 500 °C• purging cycles

• water• 20 °C

• hot and contaminated atmosphere

• component life 100,000 h

Loads• fatigue

• high thermally induced strains

• 5000 cycles• corrosion• oxidation

Boundary Conditions

• temperatures up to 500 °C• purging cycles• oxidative and corrosive

environment• component life 100,000 h

Materials• substrate 16Mo3 (1.5415)

• low alloyed• heat resistant

• braze alloy Ni660• Ni-19Cr-7.3Si-1.5B• 38 µm thick

• subsequent heat treatment after brazing (aluminising)

Technological Environment

Page 4

weld design

braze design

burner hub

temperature distribution

during purging



Diffusion Brazing

Characteristics

• diffusion driven process• isothermal solidification

• microstructure comparable to base alloy no brittle phases

• structural joining• extended solidification times for wide

gaps• w0 = 300 µm tiso ≈ 50 h

1 2 widening2 maximum joint width, wmax2 4 isothermal solidification4 solidified joint, tiso5 homogenisation of solid

⎟⎠⎞

⎜⎝⎛

RTQwtiso exp~ 2

0

sche

me

of is

othe

rmal

sol

idifi

catio

n



Simulation and Experimental Methods

Experiments• determination of brazing parameters

• braze material• process window within tB -TB space via

full factorial 22 DoE with centre point• metallographical investigation• measurement of element distribution• process robustness with respect to joint width• mechanical testing

Simulation• calculation of phase diagrams

• Thermo-Calc Vers. S• TTNi7, TCFe7

• simulation of brazing process and subsequent heat treatment

• DICTRA 26• TTNi7 with MobNi1• moving boundary problem

½ w0 l >> w0

L γ-Fe

linear grid

geometrical grid

T3

T2

T1

TB/ °C

√tB / s½√t1 √t2 √t3

DoE

DIC

TRA

mod

el moving interface



Optimum Brazing Temperature

• typical shape of the curve, i.e. kinetics vs. solubility of the melting point depressant

• Topt ≈1300 °C

DoE

• isothermal solidification for t2 < t < t3• lower temperatures result in longer tiso

Process Characterisation

T3

T2

T1

TB/ °C

√tB / s½

√t1 √t2 √t32000

2500

3000

3500

4000

T / °C

t iso

/ s

T 1 T 3 1300l



T3

T2

T1

TB/ °C

√tB / s½

√t1 √t2 √t3

DoE – Experimental Results

legend:• continuous and/or large needle like borides/silicides

• discontinuous needle like borides/silicides

• discontinuous blocky borides/silicides

• joint free of any brittle phases

met

allo

grap

hica

linv

estig

atio

n of

DoE



Comparison of Simulation and Experiment

5

0

5

0

5

0

5> - - - - - < 1.5

1.5 2.02.0 2.52.5 3.03.0 3.53.5 4.0

4.0

centre

T1

T2

T3te

mpe

ratu

re

√t1 √t3√t2√time

legend:1. continuous and/or

large needle like borides/silicides

2. discontinuous needle like borides/silicides

3. discontinuous blocky borides/silicides

4. joint free of any brittle phases

cont

our p

lot a

nd s

imul

ated

t iso



Simulation of joint width dependence

• brazing time: St = 2.0• joint width: Sw = 1.4

Process Robustness

Experiment

• good mechanical properties up to 60 µm• transition to braze joint failure at 80 µm

0.0E+00

1.0E-05

2.0E-05

3.0E-05

4.0E-05

5.0E-05

6.0E-05

7.0E-05

0 20 40 60 80 100sqrt(time) / s 1̂/2

w0

/ m

16Mo3 with Ni 660 DICTRA

t3

w0 = 38 µm

margin of safety brazing time

margin of safety joint width

sqrt(time) / s^1/2

calculated limit

0

5

10

15

20

25

30

0 50 100 150

joint width / µm

A5 /

% base materialfailurebraze joint failure

16Mo3 @ RTMvision min

200

250

300

350

400

450

500

550

600

0 50 100 150

joint width / µmRm

/ M

Pa



Simulation vs. Experiment

• good agreement in regard to width of diffusion zone

• absolute values via EDX questionable

Element Distribution

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0.E+00 5.E-05 1.E-04 2.E-04 2.E-04distance / m

c /

wt.-

%

Si - t = 0 s

Si - t = tiso

Si - t = t3

Si - fully heat treatment

0

5

10

15

20

25

0.E+00 5.E-05 1.E-04 2.E-04 2.E-04distance / m

c /

wt.-

%

Cr - t = 0 s

Cr - t = tiso

Cr - t = t3

Cr - fully heat treated 0

2

4

6

8

10

12

14

0.0E+00 5.0E-05 1.0E-04 1.5E-04distance / m

c /

wt.-

%

Cr experimental

Si experimental

Cr calculated

Si calculated

Si d

istr

ibut

ion

Cr d

istr

ibut

ion



Conclusions

• systematic approach lead to significant process improvement

• isothermal solidification is crucial for mechanical properties

• simulations can assist definition of process window and CTQs such as TB , tB, and joint width

• to date simulations cannot replace experiments

Outlook

• simulation of systems with in-situ precipitation of borides and other phases

• reduced experimental effort

16M

o3-N

i 660

-16M

o3LC

F pe

rfor

man

ce



Contact page

Dr. Sebastian Piegert Group Lead E F PR GT EN MT 2 4 - Joining and Repair

Huttenstraße 12 10553 Berlin

Phone: +49 (30) 3461 1089 Mobile: +49 (162) 132 62 79

E-mail: [email protected]

Page 13



Disclaimer

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Trademarks mentioned in this document are the property of Siemens AG, it's affiliates or their respective owners.

23 September 2013Page 14 Author / E F PR GT EN MT

http://www.siemens.com/

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lÖt 2013 aachen (2013-06-20) – dr. s. piegert , i...

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