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Please cite this article using:

*1

2

- 1

- 2

* 19395

- 1999 snakhodchi@kntu.ac.ir

: 07 1394

: 26 1394

: 24 1394

. . .

. 617

-

oC

1170 7500

Nmm

.

.

. .

-

Numerical and Experimental Analysis of Thermal Barrier Coatings Delamination under Cyclic Thermal Loading

Soheil Nakhodchi

^*

, Hossein Ebrahimi

Department of Mechanical Engineering, K. N. Toosi University of Technoogy, Tehran, Iran.

* P.O.B. 1999-19395, Tehran, Iran, snakhodchi@kntu.ac.ir

A

RTICLE

I

NFORMATION

A

BSTRACT

Original Research Paper Received 28 November 2015 Accepted 15 February 2016 Available Online 14 March 2016

Thermal Barrier Coatings (TBC) are used as thermal protective for components operating at high temperature. These coatings normally have three layers of: ceramic top coat, thermally grown oxide and the bond coat layer. Due to the manufacturing process and the special structure of a TBC system, failure mechanisms of these coatings are affected by both thermal and mechanical loads introduced to the coated part. In this paper delaminations of TBC layers subjected to the cyclic thermal loads have been numerically and experimentally studied. A rectangular specimen made of Inconel 617 coated by air plasma spray (APS) method was loaded in a specific design test setup with capability of simultaneously applying a constant four point bending load and thermal cyclic loadings. The thermal cycles were carried out until the coating was spalled out. The temperature of the specimen surfaces was measured and recorded during the test. Finite elements modeling was also performed using ABAQUS to simulate the the experiment. A cohesive zone model was used to simulate the top coat delamination. Finally, using a trial and error approach on the cohesive properties, finite elements results have been adapted on the experimental results and interfacial cohesive properties have been estimated.

Keywords:

Thermal Barrier Coating Failure Mechanisms

Thermomechanical Cyclic Experiment Cohesive Zone Model

- 1

1

.

.

1 Thermal Barrier Coatings (TBCs)

1 ] . [

50

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

.

1

1960 .

. 70 . .

1 ] . [

.

2

3

4

-

. 5 m

0 .

100 µm

500 µm ZrO

2

-8wt%Y

2

O

3

- ]

5

2 [

]

6

3 . [

MCrAlY (Pt,Ni)Al

100 µm 200 µm

MCrAlY M

.

7 8

]

9

4 . [

5 ]

- 8 . [

. 9 ] - 11 . [

1 Flame Sprayed Coatings

2 Top Coat (TC)

3 Bond Coat (BC)

4 Substrate

5 Air Plasma Spraying (APS)

6 Electron Beam Physical Vapour Deposition (EB-PVD)

7 Vacuum Plasma Spray (VPS)

8 Low-Pressure Plasma Spray (LPPS)

9 High Velocity Oxy-Fuel (HVOF)

.

o

C 1170

o

C . 20

. .

- 2

617

100 mm 10 mm

2 mm 6 .

) .( 1

"

-

"

. Ni22Cr10Al1Y

ZrO

₂

-8wt%Y

₂

O

₃

.

2

. 3

-

Fig. 1 Illustrate coating and substrate in specimen with dimensions 1

Fig. 2 Microstructure and thickness of TBC layers before tests 2

Bond Coat

190 µm Top Coat

540 µm

Substrate 6200 µm Length 100 mm

Thickness 6.9 mm

Width 10 mm

Top Coat Substrate

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

287

Fig. 3 Schematic figure of air plasma spraying process

-

3

12 ] [

. .

120 mm

×

× 120 80

15 mm

2800 rpm .

. .

.

. K

o

C

o

0 1370 C

4

. 500 N .

5

. 30 mm

.

500 N ) 5

7500 Nmm = M

B

) 9 mm 6 .

× ( 10

2

x

. 6

Fig. 4 Thermo-mechanical test setup

-

4

4

5

.

- 2 - 1

7 A

B C D E

F G c

s 15 mm

. 5 mm

. 360

-

. 8 8

A

_c

B

_c

F

_c

G

_c

D

c

D

s

9

. 7

9 . 8 9

.

- 2 - 2

.

% - 20 10

13 ] . [ 10

20

13 ] . [

Coated Specimen Heat Element

Bending Pins

Water-Cooler Anode

Work Piece Coating Cathode

Plasma Gas

Insulator Powder Port

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

Fig. 5 (a) Geometry of 4-point mechanical bending load, (b) Bending moment of applied load along the length of specimen

( )

5

( )

Fig. 6 Curve of longitudinal stress between two bending pins along thickness due to load of 500 N

6

N

500

Fig. 7 Points of temperature measurement on the specimen by considering placing on the pins

7

.

7500 Nmm 64

)

. ( 9

10

10 .

Fig. 8 Maximum temperature in points on the coating and outer surface of substrate along the length of specimen

8

Fig. 9 Temperature changes during a thermal cycle at points of

D

_c

and D

_s

9

D

c

D

s

. .

.

.

1

20 01 mm

0 . .

.

-1

1 m 0 . ) m

( 10

01 mm 0 . .

) ( 1

.

y

6 997 0 . = .

R

1 Shadow Projection Profilometry

-120 -60 0 60 120 180 240

0 1 2 3 4 5 6

Longitudinal Stress (MPa)

Thickness (mm) Substrate

Oxide Layer Bond Coat

Top Coat 450

650 850 1050 1250

0 15 30 45 60 75 90

Temperature (oC)

Distance from Point of A

_s

(mm) Substrate Coating

A

_c

B

_c

C

_c

D

_c

E

_c

F

_c

G

_c

G

_s

F

_s

E

_s

D

_s

C

_s

B

_s

A

_s

0 200 400 600 800 1000 1200

0 150 300 450 600 750 900

Temperature (oC)

Time (s)

Dc Ds

670

^o

C 1170

^o

C

Coating

Pin A Substrate

c

B

c

C

c

D

c

E

c

F

c

G

c

D

s

C

s

B

s

A

s

G

F

s

E

s s

250 N 250 N

( ) (b)

250 N (a) ( ) 250 N

30 mm 30 mm 30 mm

5 mm 5 mm

6.9 mm Substrate

Coating

7500

30 60 90

MB (Nmm)

x (mm)

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

289

) ( 1

= 4 × 10 + 8 × 10 + 2 × 10 8 × 10 7 × 10 + 0.0017 + 0.793

- 3

-

1

2

.

o

C 20 1170

910 s

10

)

o

C

Max =

10 10 s

Max =

(

.

...

- 3 - 1

( ) 11

14 15 ] . [

( ) 11 .

3

. 8

) CPE8T .(

. ) 10 .

Fig. 10 Tested specimen after 64^th cycle

10

64

1 Coupled Temperature-Displacement

2 Transient

3 Cyclic Symmetry

Fig. 11 (a) Schematic figure of different layer with dimensions, (b) Section of created model and mesh in ABAQUS

( )

11

)

1 5

11

- 3 - 2

)

o

C ( 20 .

9 9

12 .

12

4 T

.

) 5 .

.

- 3 - 3

5

1

2

3

4 Time period

5 Hybrid Method

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

Fig. 12 Schematic figure of applied thermal cycles on the top and bottom walls of model

12

16 ] . [ .

.

4

. -

. ...

16 ] . [

-

5

. 13

- .

.

- .

-

) ( 2

= ( )

-

. -

6

7

8 9

10

11

. )

( 3

1 Damage

2 Micromechanical Processes

3 Phenomenological

4 Evolution Law

5 Traction-Separation Law (TSL)

6 Damage Initiaion

7 Damage Evolution

8 Maximum Stress (MAXS)

9 Quadratic Stress (QUADS)

10 Maximum Separation (MAXU)

11 Quadratic Separation (QUADU)

Fig. 13 Traction-separation curve in general form

-

13

) ( 3

+ = 1

1

(NiCoCrAlY)

] 17 [

Table. 1 Specific heat capacity, conductance and density of bond coat (NiCoCrAlY) [17]

T

(°C)

C_p

(J/kgK)

T

(°C)

k

(W/mK)

T

(°C) (kg/m

³

)

21.3 542.9

28.1 4.3042 24.9

6189

251.7 659.2

299.5 5.9646 300.3

5664

499.6 712.1

500.4 6.9534 500.3

5844

698.6 738.5

700.5 9.7197 710.9

6423

901.1 757.5

899.9 10.6836 900.5

6479

1000.8 746.9

1100.0 13.1745 1100.9

6521

1198.8 772.0

1200.7 16.1223 1200.3

6590

2

(ZrO

2

-8wt%Y

2

O

3

(YSZ)) ]

18

[

Table. 2 Specific heat capacity, conductance and density of top coat (ZrO2-8wt%Y2O3 (YSZ)) [18]

T

(°C)

Cp

(J/kgK)

k

(W/mK) (kg/m

³

)

25.00 455.60

1.4998 4820

126.85 516.14

1.4998 4820

326.85 568.08

1.4998 4820

526.85 595.67

1.4998 4820

726.85 616.77

1.4998 4820

926.85 635.44

1.4998 4820

1126.85 652.48

1.4998 4820

1156.85 655.73

1.4998 4820

1176.85 719.84

1.4998 4820

3

-Al

2

O

3

)

] 19

[

Table. 3 Specific heat capacity, conductance and density of oxide layer -Al2O3) [19]

T

(°C)

C_p

(J/kgK)

k

(W/mK) (kg/m

³

)

20 755

33.00 3984

500 1165

11.40 3943

1000 1255

7.22 3891

1200 1285

6.67 3863

Traction

Separation Damage Evolution

Damage Initiation

….

Time

Temperature T

T

2T 3T

ts t

f

TL

TH

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

291

4

]

11

[

Table. 4 Module of elasticity, Poisson’s ratio and thermal expansion coefficient of coating layers [11]

T

(°C) (NiCoCrAlY)

-Al

2

O

3

) (ZrO

2

-8wt%Y

2

O

3

(YSZ))

E (MPa)

(1/°C)

E (MPa)

(1/°C)

E (MPa)

(1/°C)

20 151857 0.3189

1.2358×10

^-5

380365

0.27 5.0794×10

^-6

17500.0 0.2

9.6800×10

^-6

220 150746

0.3271 1.3041×10

^-5

369060 0.27

5.9040×10

^-6

16340.9

0.2 9.6748×10

^-6

420 145253

0.3343 1.3912×10

^-5

361225 0.27

6.7285×10

^-6

15181.8

0.2 9.7058×10

^-6

620 132337

0.3409 1.4970×10

^-5

351876 0.27

7.5531×10

^-6

14022.7

0.2 9.8098×10

^-6

820 108921

0.3466 1.6217×10

^-5

336032 0.27

8.3776×10

^-6

12863.6

0.2 1.0024×10

^-5

1020 71890

0.3515 1.7652×10

^-5

308708 0.27

9.2022×10

^-6

11704.5

0.2 1.0384×10

^-5

5

617

] 20

[

Table. 5 Mechanical and thermal properties of substrate Inconel 617 [20]

T

(°C)

E (MPa)

(1/°C)

Cp

(J/kgK)

k (W/mK)

(kg/m

³

)

25 211000

0.30 -

420 13.5

8360

100 206000

0.30 1.16×10

^-5

440 14.7

8360

300 194000

0.30 1.31×10

^-5

490 17.7

8360

500 181000

0.30 1.39×10

^-5

536 20.9

8360

700 166000

0.30 1.48×10

^-5

586 23.9

8360

900 149000

0.30 1.58×10

^-5

636 27.1

8360

1000 139000

0.31 1.63×10

^-5

662 28.7

8360

1100 129000

0.32 -

- -

8360

1

-

2

.

) ( 4

) ( 4

+ = 1

.

. 14 .

12 ] [

.

- 4

- 3 3 .

. .

6

1 Power Law

2 Benzeggagh-Kenane (BK)

.

- 4 - 1

.

Fig. 14 Picture provided by the Scanning Electron Microscope from

layers interface, without oxide layer formation

14

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

6

Table. 6 Results of estimation of cohesive zone properties T_s

(MPa)

T_n

(MPa)

28.25 56.5

- 1 - 2

64 .

15

S22

( )

20 35

50 . 64

. 64

15 20

64 16

S22

64 910

20

17

. 50

15 17

- 5

7500 Nmm 617

o

C

o

1170 20 C

64

.

Fig. 15 Contour of S22 Stress in first model at: (a) 20^th cycle, (b) 35^th cycle, (c) 50^th cycle, (d) 64^th cycle

15 S22

( ) : ( ) 20

( ) 35 ( ) 50

64 +1.994e+4

-1.665e+3 -4.370e+3 -7.076e+3 -9.782e+3 -1.249e+4

)

(a) (b) )

)

(c) (d) )

S₂₂

(MPa)

S₂₂

(MPa)

S22

(MPa)

S22

(MPa)

+2.051e+4 -1.709e+3 -4.471e+3 -7.233e+3 -9.995e+3 -1.276e+4

+5.751e+3 +2.041e+2 -1.657e+2 -5.355e+2 -9.054e+2 -1.275e+3

+1.710e+3 +3.883e+2 +2.486e+2 +1.090e+2 -3.067e+1 -1.703e+2

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

293

Fig. 16 Contour of S22 Stress in second model after 64 cycles 16 S₂₂

64

Fig. 17 Contour of S22 Stress in second model after 64 cycles, near the region of delamination

17 S22

64

.

.

7500 Nmm

9 64

. .

- 6

( )

.

- 7 )

J/kgK (

CPE8T

8

) ( MPa

) ( W/mK )

( MPa

)

)

) K ( °C ) K ( °C

) K ( °C

) ( 1/°C

) ( s

) ( K

) mm

^-1

(

) mm

^-1

(

) kg/m

³

(

s

- 8

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[6] Z. Lu, S.W. Myoung, Y.G. Jung, G. Balakrishnan, et al., Thermal fatigue behavior of air-plasma sprayed thermal barrier coating with bond coat species in cyclic thermal exposure, Materials, Vol. 6, No. 8, pp. 3387-3403, 2013.

S₂₂

(MPa) +1.670e+3 +1.173e+2 -4.810e+1 -2.135e+2

S₂₂

(MPa)

+1.670e+3 +1.173e+2 -4.810e+1 -2.135e+2

[ Downloaded from mme.modares.ac.ir on 2023-12-10 ]

[7] K. Sláme ka, L. elko, P. Skalka, J. Pokluda, et al., Bending fatigue failure

of atmospheric-plasma-sprayed CoNiCrAlY+ YSZ thermal barrier coatings, International Journal of Fatigue, Vol. 70, pp. 186-195, 2015.

[8] Moridi, M. Azadi, G.H. Farrahi. Thermo-mechanical stress analysis of thermal barrier coating system considering thickness and roughness effects, Surface and Coatings Technology, Vol. 243, pp. 91-99, 2014

[9] W. Zhu, L. Yang, L.W. Guo, Y.C. Zhou, et al., Determination of interfacial adhesion energies of thermal barrier coatings by compression test combined with a cohesive zone finite element model., International Journal of Plasticity, Vol. 64, pp. 76-87, 2015.

[10] P. Bednarz, Finite element simulation of stress evolution in thermal barrier coating systems, PhD Thesis, Fakultät für Maschinenwesen, 2006.

[11] M. Bia as, Finite element analysis of stress distribution in thermal barrier coatings, Surface and Coatings Technology, Vol. 202, No. 24, pp. 6002-6010, 2008.

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[15] K. Sfar, J. Aktaa, D. Munz, Numerical investigation of residual stress fields and crack behavior in TBC systems, Materials Science and Engineering, Vol.

333, No. 1, pp. 351-360, 2002.

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[18]U. Hermosilla, Mechanical modeling of thermal barrier coatings at high temperatures, PhD thesis, University of Nottingham, 2008.

[19] M. Munro, Evaluated material properties for a sintered -Al2O3, Journal of the American Ceramic Society, Vol. 80, No. 8, pp. 1919-1928, 1997.

[20] Special Metals Corporation Catalog, Inconel 617, Accessed 05 Mar 2005;

http://www.specialmetals.com/documents/Inconel%20alloy%20617.pdf.

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