Thermal Spraying for Power Generation Components (SCHNEIDER:THERMAL SPRAY O-BK) || Front Matter

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K. E. Schneider, V. Belashchenko, M. Dratwinski, S. Siegmann, A. ZagorskiThermal Spraying for Power Generation Components

Thermal Spraying for Power Generation ComponentsK. E. Schneider, V. Belashchenko, M. Dratwinski, S. Siegmann, A. ZagorskiCopyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 3-527-31337-0

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Klaus Erich Schneider, Vladimir Belashchenko,Marian Dratwinski, Stephan Siegmann,Alexander Zagorski

Thermal Spraying forPower Generation Components

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All books published by Wiley-VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

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Bibliographic information published bythe Deutsche NationalbibliothekThe Deutsche Nationalbibliothek lists this publication in the Deutsche National-bibliografi e; detailed bibliographic data are available in the Internet at http://dnb.d-nb.de.

© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfi lm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifi cally marked as such, are not to be considered unprotected by law.

Composition Manuela Treindl, LaaberPrinting Strauss GmbH, MörlenbachBinding Litges & Dopf Buchbinderei GmbH, Heppenheim

Printed in the Federal Republic of GermanyPrinted on acid-free paper

ISBN-13: 978-3-527-31337-2ISBN-10: 3-527-31337-0

Authors

Klaus Erich SchneiderKuessaberg, Germanye-mail: KlausErich.Schneider@t-online.de

Vladimir BelashchenkoConcord, NH, USAe-mail: belashchenko@comast.net

Marian DratwinskiStein, Switzerlande-mail: dratwinski@bluewin.ch

Stephan SiegmannEMPAThun, Switzerlande-mail: stephan.siegmann@empa.ch

Alexander ZagorskiALSTOMBaden, Switzerlande-mail: alexander.zagorski@power.alstom.com

CoverSimulated Spray Pattern, ALSTOM

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V

Preface

Coatings constitute an intrinsic part of the power-generation hardware. Thousands of patents, papers and conference presentations address new coating types, new hardware and software, new process developments, new chemical compositions. A huge unpublished knowledge is stored in manufacturers “know-how”.

However, sometimes coatings are still considered as an “art” and there are fair reasons for that. The thermal spray is still not a “plug and play” tool and the product quality largely depends on the deep understanding of process physics and hardware features, accumulated experience, engineer’s intuition and operator’s training.

This book now deals with questions that are essential for a good performance of this “art”:

Is there a given process stability? What is the ratio of deterministic and stochastic in the coating process?Is there an inherent process capability for a given specifi cation that cannot be improved?What is the right preventive maintenance strategy?Is there a chance to end up with coating-process capabilities in the order of other manufacturing processes?What can be predicted and designed a priori by physical modeling and offl ine programming and what can be achieved by trial and error only?What can be done to describe and control quality?

This book is not a pure scientifi c book. It is of most value for the engineer involved in design, processing and application of thermally sprayed coatings:

To understand the capability and limitations of thermal spraying, to understand deposition effi ciency – and the importance of maintenance and spare parts for quick changeover of worn equipment, to use offl ine programming and real equipment in an optimum mix to end up with stable processes in production after the shortest development time and in the end to achieve the fi nal target in production:

Process stability at minimum total cost

Klaus Schneider

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Thermal Spraying for Power Generation ComponentsK. E. Schneider, V. Belashchenko, M. Dratwinski, S. Siegmann, A. ZagorskiCopyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 3-527-31337-0

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VI Preface

Acknowledgement

The authors would like to thank the following companies and institutions for supplying valuable material – published and unpublished – for this book.

ALSTOM, Sulzer Metco, Turbocoating, CENIT, EMPA Material Science and Technology, Praxair, HC Starck, Siemens, ASM, Elsevier Publ., Stellite Coatings, Progressive Technologies, National Research Council Canada.

And personal acknowledgements to F. Stadelmaier (TACR), P. Ryan, P. Holmes, J. E. Bertilsson (ALSTOM), A. Scrivani (Turbocoating), A. Sickinger (ASA, California, USA), K. Matty (former AETC).

In particular, I would like to express my gratitude to the management and my colleagues at ALSTOM for the assistance and valuable discussions during all the years that enabled me to start this book. The production experience with offl ine programming and monitoring was only possible together with the erection and start-up of the ALSTOM coating shop in Birr, Switzerland.

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The Authors of this Book

Klaus E. Schneider received a degree in Physics and Materials Science and a PhD in Materials Science and Technology from the University of Erlangen, Germany. He has three decades of experience in manufacturing and materials technology in power and turbine engineering, mechanical engineering. During his professional carreer at BBC, ABB, ALSTOM Mannheim, Germany, and Baden, Switzerland (1974–2004), he worked in several leading positions in materials, supply management and manufacturing. He was responsible for national and international R&D programmes and for erecting new manufacturing facilities. Since 2004 he is active as a consultant for materials and manu-facturing technology.

Vladimir Belashchenko has a PhD in Physics and Chemistry of Plasma Technology and a ScD in Materials Science. He has over 30 years of experience in research, development and implementation of thermal spray equipment, materials and technologies. In 1992, he obtained the ASM International Award, in 2004 the R&D 100 Award.

Marian Dratwinski is a process development engineer with a very wide range of technical knowledge and experiences. In his current post, he is responsible for Coating Applications Development at Sulzer Metco AG in Switzerland.

Thermal Spraying for Power Generation ComponentsK. E. Schneider, V. Belashchenko, M. Dratwinski, S. Siegmann, A. ZagorskiCopyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 3-527-31337-0

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Stephan Siegmann received his degree in Physics from the Uni-versity of Basel, Switzerland. After completing the PhD in the fi eld of Thermal Spraying, he was working as Vice Manager Research at MGC Plasma Company at Muttenz, Switzerland, in the fi eld of waste treatment by thermal plasma at 1.2 MW. In the year 1994 he changed back to his former fi eld of Thermal Spraying and built up a position at the Swiss Federal Institute for Materials Science and Technology (EMPA), where he is now responsible for all Thermal Spray activities.

Alexander Zagorski received his degree in Mechanical Engineering from the Novosibirsk State Technical University and his PhD in Hydromechanics and Plasma from the Institute of Theoretical and Applied Mechanics in Novosibirsk, Russia. After having worked in Research and Development for eighteen years, he is now the Expert Engineer at the ALSTOM Customer Service Development in Switzerland.

The Authors of this Book

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IX

Contents

Preface V

The Authors of this Book VII

1 Introduction 11.1 Requirements for Materials and Coatings in Powerplants 11.2 Examples of Coatings in Gas Turbines 21.3 Defi nition of Thermal Spraying (THSP) 51.4 Thermal-Spraying Systems 51.5 Coatings for Power-Generation Components 61.6 The Complete Manufacturing and Coating Process 71.7 Coating-Process Development 121.8 Tasks for “Target” Readers 15

2 Practical Experience Today 172.1 Coating Processes 172.2 Basics of Thermal Spraying 212.3 Feedstock 232.3.1 Wire 232.3.2 Powder 242.3.2.1 Powder Types 242.3.2.2 Powder-Production Processes and Morphologies 272.3.2.3 Powder Characterization 332.3.2.4 Powders for Power-Generation Applications 362.4 Thermal-Spraying Equipment 402.4.1 Example of a Low-Pressure Plasma-Coating System 412.4.2 Flame and Arc Spray Torches 432.4.3 HVOF Process 452.4.3.1 Comparison of HVOF Fuels 472.4.3.2 A Brief Overview of the Major Existing HVOF Systems 482.4.3.3 Possible Improvements of HVOF Systems 512.4.4 Plasma Process 542.4.4.1 A Brief Overview of Plasma Torches 58

Thermal Spraying for Power Generation ComponentsK. E. Schneider, V. Belashchenko, M. Dratwinski, S. Siegmann, A. ZagorskiCopyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimISBN: 3-527-31337-0

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X Contents

2.4.4.2 Possible Improvements of Plasma Systems 632.5 Work Flow and Important Coating Hardware 652.5.1 Powder Preparation and Powder-Delivery System 682.5.1.1 Powder Preparation 682.5.1.2 Powder Delivery and Injection System 682.5.1.3 Powder Injection and Plasma/Hot Gas Jet 732.5.1.4 Injector Plugging and “Spitting” 752.5.1.5 Powder Buildup at the Front Nozzle Wall 772.5.2 Cooling System 772.5.3 Power-Supply System 792.5.4 Gas Supply and Distribution System 802.5.5 Manipulation Systems 812.5.6 Fixtures and Masking 832.6 Examples of Coated Power-Generation Components 842.7 Production Experience 862.7.1 Surface Preparation 872.7.1.1 Internal Plasma and Transferred Arc 892.7.2 Process and Systems 912.7.2.1 The Programming of the Coating Process 942.7.3 Finishing 952.7.4 Repair of Turbine Parts 952.7.4.1 Coating Removal, Stripping 972.7.4.2 Restoration of the Base Materials 982.7.4.3 Refurbishing, Recoating 982.8 Commercial 992.8.1 General 992.8.2 Surface Preparation 1032.8.3 Coating Equipment 1032.8.4 Finishing 104

3 Quality and Process Capability 1053.1 Quality Assurance 1053.2 Sources of Process Variations 1053.2.1 Special Causes of Coating-Process Variation 1073.2.2 Stochastic Nature of a Spray Process 1083.2.2.1 Arc and Jet Pulsations 1083.2.2.2 Powder-Size Distribution 1093.2.2.3 Powder Injection 1103.2.2.4 Powder Shape 1103.2.2.5 Particle Bonding 1103.2.2.6 Gun and Component Motion and Positioning 1103.2.3 Drifting 1113.2.4 Stability of the Quality Control 1123.3 Process Capability and Stable Process 1153.3.1 Defi nition of Process Capability 115

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XIContents

3.3.2 Defi nition of a Stable Coating Process 1173.3.3 Operational Window 1183.3.4 What Process Capability is Required? 1223.3.5 Additional Factors that Affect the Process Capability 1243.3.6 Case Study: Achievable Process Capability 1253.3.6.1 Part Complexity 1253.3.6.2 Mutual Position of the Gun and Component Fixtures 1253.3.6.3 Powder Quality 1253.3.6.4 Torch Pulsations and Drifting 1263.3.6.5 Instability of the Quality-Control Process 1283.3.6.6 Surface Preparation and the Part Temperature 1283.3.6.7 Conditions of the Powder-Injection System 1293.3.6.8 Process Capability 1293.4 Maintenance 130

4 Theory and Physical Trends 1334.1 Coating Formation from Separate Particles: Particle Impact,

Spreading and Bonding 1334.2 Physics of Plasma Torches 1384.2.1 Plasma Properties 1394.2.2 Gas Dynamics of Plasma Torch 1454.2.3 Energy Balance of the Plasma Gun 1474.2.4 Major Trends 1494.2.4.1 Variation of the Gun Power; the Gas Flow Rates and Composition

Unchanged 1494.2.4.2 Variation of the Plasma Composition at the Same Specifi c Plasma

Enthalpy 1494.2.4.3 Variation of the Plasma Flow Rate at Unchanged Gun Power

and Gas Composition 1504.2.4.4 Effect of Nozzle Diameter 1514.2.5 Plasma Swirl 1514.3 Structure of Plasma Jets 1514.3.1 APS Jet 1514.3.2 Structure of LPPS Jet 1534.4 Particles in Plasma 1554.4.1 Particles at APS 1564.4.2 Particle at LPPS 1584.4.2.1 Particle Acceleration and Heating in the LPPS Free Jet 1584.4.2.2 Particle Acceleration and Heating Inside the Nozzle 1604.5 Spray Footprint (Spray Pattern) 1614.6 Infl uence of Particles on Plasma Flow 1644.7 Substrate Surface Temperature 1654.8 Formation of the Coating Layer 1674.9 Use of Different Plasma Gases 1684.10 Some Distinguishing Features of HVOF Physics 169

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XII Contents

5 Offl ine Simulation of a Thermal-Spray Process 1715.1 Simulation in Production 1715.2 Physical Background of Simulation Package 1755.2.1 Viscoplasticity Model of a Splat and Particle Bonding 1755.2.2 Thermodynamic and Transport Properties of Argon/Hydrogen

Mixtures 1765.2.3 Modeling of the Plasma Gun 1765.2.4 Modeling of the Plasma Jets 1765.2.4.1 APS Jet 1775.2.4.2 LPPS Jet 1775.2.5 Acceleration and Heating of Particles in Plasma 1795.2.6 Surface Thermal Conditions 1805.3 Spray Pattern 1825.3.1 Calibration of the Bonding Model and Sensitivity of a Spray Pattern

to the Process Parameters, Spray Angle and Bonding Model 1825.3.2 Coating Porosity and Roughness 1855.4 Modeling of Turbine Blades 1875.5 Coating Thickness Optimization and Stochastic Modeling Tools 1895.6 Simulation of HVOF Process 1955.7 Use of Offl ine Simulation in Coating Development 1995.7.1 Application Areas of Modeling in the Coating Process 1995.7.1.1 Coating Defi nition and Design for Coating 1995.7.1.2 Coating-Process Development 1995.7.1.3 Part Development 2005.7.1.4 Physical Modeling and Offl ine Simulation as Process-Diagnostic

Tools 2015.7.1.5 Simulation as a Numerical Experiment 2015.7.1.6 When the Offl ine Simulation Should Be Used 202

6 Standards and Training 2056.1 Standards, Codes 2056.1.1 Introduction to Standards 2056.1.2 Quality Requirements for Thermally Sprayed Structures and

Coating Shops 2066.1.3 Qualifi cation and Education of Spraying Personnel 2096.2 Special Case: Spraying for Power-Generation Components 2116.2.1 Coating-Process Development 2126.2.2 Coating Production 2136.2.3 General Requirements for Coating-Shop Personnel 213

7 Monitoring, Shopfl oor Experience and Manufacturing Process Development 215

7.1 Monitoring, Sensing 2157.1.1 Introduction of Monitoring 2157.1.2 Particle-Monitoring Devices 217

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7.1.3 Infl uence of Spray Parameters on Particle Speed and Temperature 218

7.1.4 Infl uence of Particle Velocity and Temperature on Microstructure 219

7.2 How to Use Monitoring for Process Control 2227.2.1 Monitoring, Sensing from a Job Shop Point of View 2227.2.2 Vision for Future Coating Control and Monitoring 2247.3 Manufacturing Coating Development 2287.3.1 Coating Development Process 2297.3.2 Coating Defi nition and Coating Specifi cation;

Design for Coating 2307.3.3 Process Development 2337.3.3.1 Powder Selection 2347.3.3.2 Torch Parameters 2347.3.3.3 Spray Pattern and Standoff Distance 2347.3.3.4 Coating Mono-Layer; Powder Feed Rate and Traverse Gun Speed 2357.3.3.5 Spray Trials and Coating Qualifi cation 2357.3.3.6 Sensitivity Checks 2367.3.4 Part Development 2367.3.4.1 Coating Program 2367.3.4.2 Process Qualifi cation and Preserial Release 2377.3.5 Serial Release 239

8 Outlook, Summary 2418.1 Thermal Spray Torches 2428.2 Future Offl ine Programming and Monitoring in Process

Development and Production 244

References 245

Subject Index 261

Contents

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Disclaimer

While every precaution has been taken in the preparation of this book, the publisher and the authors assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein.

As far as the authors of this book specify products of third parties they merely provide a description pertaining to this book. They do not want to promote or advertise any product or are liable for specifi c qualities of these products. In no event the authors are liable for damages suffered or personal injury including every kind of damages, especially consequential damages, arising out of the use or the inability to use these products. The same applies to the facts and information taken from foreign authority. The authors do not guarantee that the provided facts and information is state of the art, correct, complete or the quality thereof.

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