Modeling decohesion of a top-coat from a thermally-growing oxide in a thermal barrier coating

Khaled Al-Athel; Kaspar Loeffel; Haowen Liu; Lallit Anand

doi:10.1016/j.surfcoat.2013.02.005

Modeling decohesion of a top-coat from a thermally-growing oxide in a thermal barrier coating

Khaled Al-Athel, Kaspar Loeffel, Haowen Liu, Lallit Anand^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

58 Scopus citations

Abstract

Oxidation of the bond-coat and the shape-distortion which accompanies the growth of the oxide is a major mechanism which causes local interfacial decohesion between the ceramic top-coat and the growing oxide layer in a thermal barrier coating. The objective of this paper is to numerically study the growth of the oxide and the induced decohesion of the top-coat from a bond-coat which is not perfectly flat but has an initial sinusoidal-shaped surface undulation. Our numerical simulation study accounts for: (a) the diffusion of oxygen; (b) the oxidation of the bond-coat; (c) the anisotropic growth and the associated stresses and shape-distortion of the thermally-grown-oxide; (d) creep of the top-coat; and (e) the interfacial traction-separation response between the top-coat and the growing oxide.A parametric study is conducted by varying the amplitude of the initial sinusoidal undulation at the interface between the top-coat and the bond-coat. Our simulation results show that the decohesion of the top-coat depends strongly on the amplitude of the initial undulation - imperfections with a larger initial amplitude prove to be more detrimental.Our numerical study suggests that in order to improve the delamination-life of an air-plasma-sprayed thermal barrier coating it might be beneficial to produce bond-coat surfaces with shallow and evenly distributed dimples - rough enough to provide adherence of the top-coat to the bond-coat via a mechanical-keying effect, but not too rough so that it leads to excessive shape-distortion and premature decohesion. This may be accomplished by using shot-peening, so as to plastically-deform and reduce the roughness of the as-deposited bond-coat surface.

Original language	English
Pages (from-to)	68-78
Number of pages	11
Journal	Surface and Coatings Technology
Volume	222
DOIs	https://doi.org/10.1016/j.surfcoat.2013.02.005
State	Published - 15 May 2013

Bibliographical note

Funding Information:
The help of Professor Sanjay Sampath and Dr. Gopal Dwivedi of SUNY Stony Brook in providing us with TBC samples is gratefully acknowledged, as is the help of Claudio Di Leo on several aspects of our research. The authors would like to thank the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia , for partially funding the research reported in this paper through the Center for Clean Water and Clean Energy at MIT and KFUPM under project number R9-CE-08 . Support from NSF (CMMI award no. 019646-001 ) is also gratefully acknowledged.

Keywords

Decohesion
Diffusion
Elastic-plastic deformation
Finite-element analysis
Oxidation
Thermal-barrier coating

ASJC Scopus subject areas

General Chemistry
Condensed Matter Physics
Surfaces and Interfaces
Surfaces, Coatings and Films
Materials Chemistry

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10.1016/j.surfcoat.2013.02.005

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title = "Modeling decohesion of a top-coat from a thermally-growing oxide in a thermal barrier coating",

abstract = "Oxidation of the bond-coat and the shape-distortion which accompanies the growth of the oxide is a major mechanism which causes local interfacial decohesion between the ceramic top-coat and the growing oxide layer in a thermal barrier coating. The objective of this paper is to numerically study the growth of the oxide and the induced decohesion of the top-coat from a bond-coat which is not perfectly flat but has an initial sinusoidal-shaped surface undulation. Our numerical simulation study accounts for: (a) the diffusion of oxygen; (b) the oxidation of the bond-coat; (c) the anisotropic growth and the associated stresses and shape-distortion of the thermally-grown-oxide; (d) creep of the top-coat; and (e) the interfacial traction-separation response between the top-coat and the growing oxide.A parametric study is conducted by varying the amplitude of the initial sinusoidal undulation at the interface between the top-coat and the bond-coat. Our simulation results show that the decohesion of the top-coat depends strongly on the amplitude of the initial undulation - imperfections with a larger initial amplitude prove to be more detrimental.Our numerical study suggests that in order to improve the delamination-life of an air-plasma-sprayed thermal barrier coating it might be beneficial to produce bond-coat surfaces with shallow and evenly distributed dimples - rough enough to provide adherence of the top-coat to the bond-coat via a mechanical-keying effect, but not too rough so that it leads to excessive shape-distortion and premature decohesion. This may be accomplished by using shot-peening, so as to plastically-deform and reduce the roughness of the as-deposited bond-coat surface.",

keywords = "Decohesion, Diffusion, Elastic-plastic deformation, Finite-element analysis, Oxidation, Thermal-barrier coating",

author = "Khaled Al-Athel and Kaspar Loeffel and Haowen Liu and Lallit Anand",

note = "Funding Information: The help of Professor Sanjay Sampath and Dr. Gopal Dwivedi of SUNY Stony Brook in providing us with TBC samples is gratefully acknowledged, as is the help of Claudio Di Leo on several aspects of our research. The authors would like to thank the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia , for partially funding the research reported in this paper through the Center for Clean Water and Clean Energy at MIT and KFUPM under project number R9-CE-08 . Support from NSF (CMMI award no. 019646-001 ) is also gratefully acknowledged.",

year = "2013",

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doi = "10.1016/j.surfcoat.2013.02.005",

language = "English",

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pages = "68--78",

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T1 - Modeling decohesion of a top-coat from a thermally-growing oxide in a thermal barrier coating

AU - Al-Athel, Khaled

AU - Loeffel, Kaspar

AU - Liu, Haowen

AU - Anand, Lallit

N1 - Funding Information: The help of Professor Sanjay Sampath and Dr. Gopal Dwivedi of SUNY Stony Brook in providing us with TBC samples is gratefully acknowledged, as is the help of Claudio Di Leo on several aspects of our research. The authors would like to thank the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia , for partially funding the research reported in this paper through the Center for Clean Water and Clean Energy at MIT and KFUPM under project number R9-CE-08 . Support from NSF (CMMI award no. 019646-001 ) is also gratefully acknowledged.

PY - 2013/5/15

Y1 - 2013/5/15

N2 - Oxidation of the bond-coat and the shape-distortion which accompanies the growth of the oxide is a major mechanism which causes local interfacial decohesion between the ceramic top-coat and the growing oxide layer in a thermal barrier coating. The objective of this paper is to numerically study the growth of the oxide and the induced decohesion of the top-coat from a bond-coat which is not perfectly flat but has an initial sinusoidal-shaped surface undulation. Our numerical simulation study accounts for: (a) the diffusion of oxygen; (b) the oxidation of the bond-coat; (c) the anisotropic growth and the associated stresses and shape-distortion of the thermally-grown-oxide; (d) creep of the top-coat; and (e) the interfacial traction-separation response between the top-coat and the growing oxide.A parametric study is conducted by varying the amplitude of the initial sinusoidal undulation at the interface between the top-coat and the bond-coat. Our simulation results show that the decohesion of the top-coat depends strongly on the amplitude of the initial undulation - imperfections with a larger initial amplitude prove to be more detrimental.Our numerical study suggests that in order to improve the delamination-life of an air-plasma-sprayed thermal barrier coating it might be beneficial to produce bond-coat surfaces with shallow and evenly distributed dimples - rough enough to provide adherence of the top-coat to the bond-coat via a mechanical-keying effect, but not too rough so that it leads to excessive shape-distortion and premature decohesion. This may be accomplished by using shot-peening, so as to plastically-deform and reduce the roughness of the as-deposited bond-coat surface.

AB - Oxidation of the bond-coat and the shape-distortion which accompanies the growth of the oxide is a major mechanism which causes local interfacial decohesion between the ceramic top-coat and the growing oxide layer in a thermal barrier coating. The objective of this paper is to numerically study the growth of the oxide and the induced decohesion of the top-coat from a bond-coat which is not perfectly flat but has an initial sinusoidal-shaped surface undulation. Our numerical simulation study accounts for: (a) the diffusion of oxygen; (b) the oxidation of the bond-coat; (c) the anisotropic growth and the associated stresses and shape-distortion of the thermally-grown-oxide; (d) creep of the top-coat; and (e) the interfacial traction-separation response between the top-coat and the growing oxide.A parametric study is conducted by varying the amplitude of the initial sinusoidal undulation at the interface between the top-coat and the bond-coat. Our simulation results show that the decohesion of the top-coat depends strongly on the amplitude of the initial undulation - imperfections with a larger initial amplitude prove to be more detrimental.Our numerical study suggests that in order to improve the delamination-life of an air-plasma-sprayed thermal barrier coating it might be beneficial to produce bond-coat surfaces with shallow and evenly distributed dimples - rough enough to provide adherence of the top-coat to the bond-coat via a mechanical-keying effect, but not too rough so that it leads to excessive shape-distortion and premature decohesion. This may be accomplished by using shot-peening, so as to plastically-deform and reduce the roughness of the as-deposited bond-coat surface.

KW - Decohesion

KW - Diffusion

KW - Elastic-plastic deformation

KW - Finite-element analysis

KW - Oxidation

KW - Thermal-barrier coating

UR - https://www.scopus.com/pages/publications/84875804420

U2 - 10.1016/j.surfcoat.2013.02.005

DO - 10.1016/j.surfcoat.2013.02.005

M3 - Article

AN - SCOPUS:84875804420

SN - 0257-8972

VL - 222

SP - 68

EP - 78

JO - Surface and Coatings Technology

JF - Surface and Coatings Technology

ER -

Modeling decohesion of a top-coat from a thermally-growing oxide in a thermal barrier coating

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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