1
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`UTC 2035
`General Electric v. United Technologies
`IPR2016-01289
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`UTC 2035
`General Electric v. United Technologies
`IPR2016-01289
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`Progress in Materials Science 46 (2001) 505—553
`
`Progress in
`Mqtenols
`
`www.elsevier.com/locate/pmatsci
`
`; Mechanisms controlling the durability of
`'
`thermal barrier coatings
`
`A.G. Evans 3”“, D.R. Mumm 3, J.W. Hutchinson b,
`G.H. Meier C, F.S. Pettitc
`
`“Materials Institute. Princeton University, Princeton, NJ 08540, USA
`‘
`_ l’Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA
`.; artment of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA
`
`'
`
`Received 25 August 2000; accepted 10 October 2000
`
`r
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`I act
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`7 e durability of thermal barrier coatings is governed by a sequence of crack nucleation,
`agation and coalescence events that accumulate prior to final failure by large scale buck-
`j.; and spalling. Because of differing manufacturing approaches and operating scenarios,
`'7 ral specific mechanisms are involved. These mechanisms have begun to be understood. This
`reviews this understanding and presents relationships between the durability, the gov-
`ing material properties and the salient morphological features. The failure is ultimately
`' nected to the large residual compression in the thermally grown oxide through its roles in
`lifying imperfections near the interface. This amplification induces an energy release rate at
`ks emanating from the imperfections that eventually buckle and spall the TBC. © 2001
`sevier Science Ltd. All rights reserved.
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`.Vr‘ .
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`1‘ ntents
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`l I
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`. Background..................................................................................................... ..507
`1.1. The system .............................................................................................. ..507
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`1.2. Failure phenomena ................................................................................. ..511
`
`tj‘
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`"‘ Corresponding author. Tel.: + 1-609-258-4762; fax: + 1-609-258—1177.
`E-mail address: anevans(iitprinceton.edu (A.G. Evans).
`
`0079-6425/01/$ - see front matter QC“ 2001 Elsevier Science Ltd. All rights reserved.
`PII: 50079-6425(00)00020-7
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`506
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`AG. Evans 91 (II. / Progress in Materials Sr'iem'r) 46 (200] ) 5057553
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`1.2.1. Generalities .................................................................................. ..511
`1.2.2. Specific mechanisms ..................................................................... ..513
`1.2.3. Related observations .................................................................... ..514
`1.3. Overarching principles ........................................................................... ..516
`
`2. Thermally grown oxides ................................................................................. ..517
`2.1. Growth phenomena ................................................................................ ..517
`
`2.1.1. Thermodynamics .......................................................................... ..518
`
`2.2. Stresses .................................................................................................... ..521
`
`2.2.1. Thermal expansion misfit stresses around imperfections ............. ..522
`2.2.2. Redistribution of misfit stresses by bond coat visco-plasticity ..... ..523
`2.2.3. Growth stresses ............................................................................ ..524
`
`2.2.4. Creep relaxation ........................................................................... ..527
`2.3. Adhesion ................................................................................................. ..528
`
`2.3.1. Metal/oxide interfaces .................................................................. ..528
`2.3.2. Mechanics .................................................................................... ..529
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`2.3.3. Test protocols ............................................................................... ..530
`2.3.4. Measurements .............................................................................. ..531
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`2.4. Failure ..................................................................................................... ..531
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`3. TBC failure mechanisms ................................................................................. ..532
`
`3.1. TBC properties ....................................................................................... ..532
`3.1.1. Stress/strain relationships ............................................................. ..532
`3.1.2. Fracture resistance ....................................................................... ..533
`3.2. The role of imperfections ........................................................................ ..535
`3.3. Stresses, cracking and failure ................................................................. ..538
`
`References ........................................................................................................... .549
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`4. Closure ............................................................................................................ ..542
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`Appendix A. Small scale buckling ....................................................................... ..543
`A1. Buckling maps ......................................................................................... ..543
`A2. Role of imperfections ................. ..a‘.......................................................... ..544
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`Appendix B. Stresses ........................................................................................... ..545
`Bl. Thermal expansion misfit ........................................................................ ..545
`B2. Oxide growth .......................................................................................... ..546
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`Appendix C. Stress intensity factors .................................................................... ..547
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`Appendix D. TGO creep/growth dynamics ......................................................... ..548
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`Appendix E. Ratcheting ...................................................................................... ..549
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`3
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