© 2002 ASM International. All Rights Reserved. Protective Coatings for Turbine Blades (#06738G)

Protective Coatings for Turbine Blades

Y. Tamarin

Materials Park, Ohio 44073–0002 www.asminternational.org

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© 2002 ASM International. All Rights Reserved. Protective Coatings for Turbine Blades (#06738G)

Copyright 䉷 2002 by ASM International威 All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the copyright owner. First printing, September 2002

Great care is taken in the compilation and production of this book, but it should be made clear that NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE GIVEN IN CONNECTION WITH THIS PUBLICATION. Although this information is believed to be accurate by ASM, ASM cannot guarantee that favorable results will be obtained from the use of this publication alone. This publication is intended for use by persons having technical skill, at their sole discretion and risk. Since the conditions of product or material use are outside of ASM’s control, ASM assumes no liability or obligation in connection with any use of this information. No claim of any kind, whether as to products or information in this publication, and whether or not based on negligence, shall be greater in amount than the purchase price of this product or publication in respect of which damages are claimed. THE REMEDY HEREBY PROVIDED SHALL BE THE EXCLUSIVE AND SOLE REMEDY OF BUYER, AND IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHETHER OR NOT CAUSED BY OR RESULTING FROM THE NEGLIGENCE OF SUCH PARTY. As with any material, evaluation of the material under end-use conditions prior to specification is essential. Therefore, specific testing under actual conditions is recommended. Nothing contained in this book shall be construed as a grant of any right of manufacture, sale, use, or reproduction, in connection with any method, process, apparatus, product, composition, or system, whether or not covered by letters patent, copyright, or trademark, and nothing contained in this book shall be construed as a defense against any alleged infringement of letters patent, copyright, or trademark, or as a defense against liability for such infringement. Comments, criticisms, and suggestions are invited, and should be forwarded to ASM International. Prepared under the direction of the ASM International Technical Book Committee (2001–2002), Charles A. Parker, Chair ASM International staff who worked on this project included Steve Lampman, Manager of Book Acquisitons; Bonnie Sanders, Manager of Production; Carol Terman, Production Project Manager; and Scott Henry, Assistant Director of Reference Publications. Library of Congress Cataloging-in-Publication Data Tamarin, Y. Protective coatings for turbine blades / Y. Tamarin. p. cm. Includes bibliographical references and index. 1. Aircraft gas-turbines—Blades. 2. Protective coatings. 3. Gas-turbines—Materials. I. ASM International. II. Title. TL709.5.B6 T36 2002 629.134⬘353—dc21 2002027690 ISBN: 0–87170–759–4 SAN: 204–7586 ASM International威 Materials Park, OH 44073–0002 www.asminternational.org Printed in the United States of America Cover: Test blades (shiny) in a low-pressure turbine. Source: Advances in Turbine Materials, Design, and Manufacturing, Proceedings of the Fourth International Charles Parsons Turbine Conference, The institute of Materials, 1997

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© 2002 ASM International. All Rights Reserved. Protective Coatings for Turbine Blades (#06738G)

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Contents Foreword....................................................................................................................... v Preface......................................................................................................................... vi Chapter 1: Introduction.................................................................................................... 1 Chapter 2: Choosing Optimum Coatings for Modern Aircraft Engine Turbine Blades................. 5 Conditions of Turbine Blade Operation ............................................................... 5 Requirements Imposed on Turbine Blade Coatings................................................ 8 Principles of Choosing Coatings for Aircraft Engine Turbine Blades ........................ 8 Causes of Coating Failures on Aircraft-Engine Turbine Blades.............................. 10 Chapter 3: Technological Processes for Deposition of Protective Coatings to Turbine Blades .... 25 Diffusion Coatings ........................................................................................ 25 Overlay Coatings .......................................................................................... 38 Chapter 4: Phase Composition and Structure of Coatings on Superalloys ............................... 55 Phase Composition and Structure of Diffusion Coatings....................................... 55 Phase Composition and Structure of Ni-Cr-Al, Ni-Co-Cr-Al, and Co-Ni-Cr-Al Alloys and Overlay Coatings Made of Them...................................................... 69 Phase Composition and Structure of Overlay Coatings......................................... 71 Chapter 5: Phase and Structural Changes in Coatings during High-Temperature Tests .............. 79 Changes of Phase Composition and Structure in Diffusion Coatings....................... 80 Changes of Phase Composition and Structure in Overlay Coatings at HighTemperature Tests ......................................................................................... 87 Chapter 6: Turbine Blade Coating Protective Properties ...................................................... 97 Protective-Properties Evaluation Methods .......................................................... 97 Heat Resistance of Aluminides and Alloys for Overlay Coatings ..........................100 Heat Resistance of Coated Superalloys.............................................................106 Resistance of Overlay-Coated Alloys to Hot Corrosion .......................................109 Resistance of Coated Superalloys to Hot Corrosion ............................................113 Chapter 7: The Effect of Protective Coatings on the Mechanical Properties of Superalloys .......119 Thermal Expansion Coefficients and Elasticity Modulus of Coating Alloys ............120 Mechanical Properties of Coating Alloys ..........................................................124 Thermal Stresses in Superalloy Coatings ..........................................................128 Effect of Coatings on High-Temperature Strength of Superalloys..........................134 iii

© 2002 ASM International. All Rights Reserved. Protective Coatings for Turbine Blades (#06738G)

iv / Protective Coatings for Turbine Blades

Effect of Coatings on Fatigue Strength of Superalloys ........................................138 Effect of Coatings on Thermal Fatigue of Superalloys ........................................142 Coating Effect on Thermomechanical Fatigue of Superalloys ...............................150 Chapter 8: Electron Beam Thermal Barrier Coatings..........................................................161 Ceramics for EB Evaporation .........................................................................162 Main Features of TBC Deposition Technique ....................................................165 Thermophysical Properties of Condensed Ceramics ............................................175 TBC Ceramic Layer Durability .......................................................................180 Chapter 9: Some Principles of Strength Designing for Turbine-Blade Protective Coatings ........195 Calculation of Stresses and Strains in Coatings..................................................195 Thermal Barrier Coatings ..............................................................................203 Appendix....................................................................................................................211 Index .........................................................................................................................217

iv

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Protective Coatings for Turbine Blades

06738G

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