Design of Thermal Barrier Coatings: A Modelling Approach

93 Pages·2015·3.939 MB·English

by  Mohit Gupta (auth.)

SPRINGER BRIEFS IN MATERIALS
Mohit Gupta
Design of
Thermal Barrier
Coatings
A Modelling
Approach
123
SpringerBriefs in Materials

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Mohit Gupta
Design of Thermal Barrier
Coatings
A Modelling Approach
Mohit Gupta
University West
Trollhättan , Sweden
ISSN 2192-1091 ISSN 2192-1105 (electronic)
SpringerBriefs in Materials
ISBN 978-3-319-17253-8 ISBN 978-3-319-17254-5 (eBook)
DOI 10.1007/978-3-319-17254-5
Library of Congress Control Number: 2015937967
Springer Cham Heidelberg New York Dordrecht London
© The Author(s) 2015
T his work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of
the material is concerned, specifi cally the rights of translation, reprinting, reuse of illustrations, recitation,
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does not imply, even in the absence of a specifi c statement, that such names are exempt from the relevant
protective laws and regulations and therefore free for general use.
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Springer International Publishing AG Switzerland is part of Springer Science+Business Media
(www.springer.com)
Dedicated to my beloved parents
Smt. (Late) Raj Kumari Gupta and Shri Ram
Niwas Gupta

Pref ace
T hermal barrier coatings (TBCs) are now key elements in the design of advanced
gas turbines. TBCs are used in a wide variety of modern gas turbine applications
such as power generation, marine and aero engines. Applications of TBCs result in
higher gas turbine effi ciency as well as enhanced lifetime of components due to the
thermal protection provided by TBCs. An extensive research is being carried out in
this fi eld to continue the implementation of new and advanced coating systems to
achieve even lower emissions as well as fuel costs.
A high performance TBC would exhibit low thermal conductivity, high strain
tolerance and long lifetime. Thus, these three properties need to be optimised by
controlling the microstructure defects which control the thermal–mechanical prop-
erties of TBCs as well as the topcoat–bondcoat interface roughness which controls
the lifetime of TBCs. The purpose of this book is to describe a design methodology
which could be implemented to obtain an optimised TBC to be used for next gen-
eration gas turbines.
C hapter 1 introduces the topic in detail and describes the scope of this book.
A general background knowledge about the processing technology and materials in
TBCs is given in Chap. 2 . The characteristics of TBCs in terms of microstructure,
properties and failure mechanisms are discussed in Chap. 3 . The experimental
methods commonly used to characterise TBCs are described briefl y in Chap. 4 .
Chapter 5 describes a modelling approach to design the thermal–mechanical
properties of TBCs which consists of real microstructure images as well as artifi -
cially created images, and the results are obtained by using that approach. Chapter
6 describes a modelling approach to design the topcoat–bondcoat interface rough-
ness in TBCs which consists of real interface roughness profi les, and the results are
obtained by implementing that approach. Chapter 7 describes a diffusion-based
modelling approach to study oxide formation in TBCs during service conditions,
and the results are obtained by implementing that approach. The conclusions from
the modelling approach described in this book are given in the last chapter as a
methodology to design an optimised TBC.
T his work was performed at the Production Technology Centre (PTC), Trollhättan,
as a part of the Thermal Spray research group at University West. The major portion
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viii Preface
of this work was done during the doctoral studies of the author. The author would like
to express his gratitude to his main supervisor during his doctoral studies, Prof. Per
Nylén, for his guidance, great support and valuable suggestions during this work.
Trollhättan, Sweden Mohit Gupta
25th February 2015
Contents
1 Introduction ................................................................................................. 1
1.1 Scope and Limitations .......................................................................... 4
References ....................................................................................................... 5
2 Background ................................................................................................. 7
2.1 Thermal Spraying ................................................................................. 7
2.1.1 Atmospheric Plasma Spraying ................................................. 7
2.1.2 High Velocity Oxy-Fuel Spraying ........................................... 9
2.1.3 Liquid Feedstock Plasma Spraying .......................................... 9
2.2 Thermal Barrier Coatings .................................................................... 9
2.3 Coating Formation ............................................................................... 11
2.4 Process Parameters ............................................................................... 11
2.5 Coating Materials for TBCs ................................................................. 12
2.5.1 Topcoat ..................................................................................... 12
2.5.2 Bondcoat .................................................................................. 14
2.5.3 Thermally Grown Oxides......................................................... 14
References ....................................................................................................... 15
3 Characteristics of TBCs.............................................................................. 17
3.1 Microstructure ...................................................................................... 17
3.2 Heat Transfer Mechanism .................................................................... 20
3.2.1 General Theory ........................................................................ 20
3.2.2 Application to TBCs ................................................................ 22
3.3 Mechanical Behaviour ......................................................................... 23
3.3.1 Stress Formation ...................................................................... 23
3.3.2 Young’s Modulus ..................................................................... 24
3.3.3 Non-linear Properties ............................................................... 25
3.4 Interface Roughness ............................................................................. 26
3.4.1 Roughness Relationship with Lifetime .................................... 26
3.4.2 Stress Inversion Theory ............................................................ 27
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