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Solving Problems in Surface Engineering and Tribology by Means of Analytical Electron Microscopy Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 12 Solving Problems in Surface Engineering and Tribology by Means of Analytical Electron Microscopy ERNESTO CORONEL ACTA UNIVERSITATIS UPSALIENSIS ISSN 1651-6214 UPPSALA ISBN 91-554-6148-4 2005 urn:nbn:se:uu:diva-4785 !""# "$ # % % % & ' ( ) * ' + *' !""#' & % * ( % , * ' , ' !' -1 ' ' ./0 1 2##324 3-23 . ) 5 ) % % ' '' % % % ) % % %% % %% % ' . ) 5 ) % %' + ) ' ( % 2% (+ ) ) % % ' 6 ) ) ) % % (+ ' ( % % % (/! ) ) ' ) 7( ,8+$+ ) % % ,( 93 ) - % ' , % ) % % ) ' ( ) % ' + 2 % % ' , :" + 2 % ) ) % ' % ) % % ) % ) ' ;+<+ % 5 % 5 + % % ' + ) ) % % ) ) 5 ' ( * % * + ! ! " ! # $ %&'! ! ()%*+* ! = * + !""# .0 4# 24! 3 ./0 1 2##324 3-23 $ $$$ 23>-# 7 $<< '5'< ? @ $ $$$ 23>-#8 Till min familj List of Papers I The effect of carbon content on the microstructure of hydrogen- free titanium carbide films grown on high speed steel by physical vapour deposition E. Coronel, U. Wiklund and E. Olsson, In manuscript II Microstructure of d.c. magnetron sputtered TiB2 coatings M. Berger, E. Coronel and E. Olsson, Surface & Coatings Technol- ogy, 180, (2004), 240-244 III An analytical TEM study of (Ta,Al)C:C coatings in as-deposited and oxidised states E. Coronel, D. Nilsson, S. Csillag and U. Wiklund, In manuscript IV TEM studies of tribofilm formation - compatibility between two metal doped DLC coatings and lubricant E. Coronel, N. Stavlid and U. Wiklund, In manuscript V On the wear mechanisms of CVD diamond when sliding in nitro- gen and argon atmosphere E. Coronel and J. Andersson and U. Wiklund, In manuscript VI Surface analysis of laser cladded Stellite exposed to self-mated high load dry sliding D. Persson, E. Coronel, S. Jacobson and S. Hogmark, Submitted to Wear VII Wear induced material modification of cemented carbide rock drill buttons U. Beste, E. Coronel and S. Jacobson, Accepted for publication in International journal of refractory metals and hard materials The author of this thesis has performed all high resolution analytical electron microscopy of all papers. Contents Part I Background 9 I.1 Introduction 11 I.1.1 Tribology 11 I.1.2 Surface Modification 12 I.1.3 The Active Surface 13 I.1.4 Tribological Testing 13 General 13 Tests used in this thesis 14 I.1.5 Tribofilm Analysis 15 I.2 Surface Engineering 17 I.2.1 Deposition of Coatings 17 Magnetron Sputtering 17 Electron beam evaporation 18 CVD 19 Laser Powder Cladding 20 I.3. Analytical Microscopy 21 I.3.1 Electron Scattering 21 Elastic Scattering 22 Inelastic Scattering 25 I.3.2 Microscopical Techniques 26 Transmission ElectronMicroscopy 27 Scanning Electron Microscopy 28 Focused Ion Beam 28 Conventional TEM sample preparation 30 I.3.3 Energy Dispersive X-ray Spectroscopy 31 I.3.4 Electron Energy Loss Spectroscopy 32 Thickness measurements 34 Relative Quantification 35 I.3.5 Energy Filtered TEM 36 Three Windows Technique 37 Part II Contributions 39 II.1 Introduction 41 II.2 Structure and composition of as-deposited and heat treated thin coatings (Papers I, II, III) 41 II.2.1 Effect of carbon content on the microstructure of TiC coatings (Paper I) 41 Conclusions 45 II.2.2 Effect of substrate bias on the microstructure of TiB2 coatings (Paper II) 45 Conclusions 47 II.2.3 The role of Al on structure and stability of (Ta,Al)C:C coatings (Paper III) 47 As-deposited coating 48 Heat treated coatings 50 Conclusions 51 II.3 Revealing mechanisms of friction and wear (Papers IV, V, VI) 53 II.3.1 Mechanisms of tribofilm formation for lubricated Me-DLC coatings (Paper IV) 53 Surface morphology of tribofilms 54 Structure of tribofilms 54 Composition of tribofilms 55 Conclusions 58 II.3.2 Wear mechanisms of diamond surfaces in different atmospheres (Paper V) 59 Sliding tests 59 Analysis of wear debris 60 Internal film characterizations 61 Composition of diamond surface 61 Conclusions 62 II.3.3 Friction mechanisms of Stellite 21 (Paper VI) 62 Sample preparation 62 Microstructure 63 Composition 63 Conclusions 65 II.4 Solution of a practical problem-Wear of cemented carbide in rock drilling (PaperVII) 67 II.4.1 Rock drilling- A tough application of cemented carbide 67 II.4.2 Sample Preparation 68 II.4.3 Wear mechanisms of drill buttons 68 Drilling quartzitic granite 68 Drilling magnetite 70 II.4.4 Conclusions 70 II.5 Summary of Contributions 71 II.6 Future challenges of HR-TEM 72 Sammanfattning på svenska 73 Bakgrund 73 Bidrag och resultat 74 Acknowledgements 77 References 79 Part I Background I.1 Introduction The development of new materials and surface layers is one of the most sig- nificant motors for the technical progress of our society. New materials may be developed by curiosity or even by chance, but much more often as a re- spond to pronounced demands. The demands are of several categories; eco- nomical (longer life, lower price, easier to machine, etc.) technical (higher performance, lighter, stronger, less prone to wear and corrosion, etc.) and – today of increasing importance – environmental and health related (non- toxic, renewable, etc.). Successful development of new and improved materials is a complicated activity, requiring the collected efforts and skills from people of several fields of expertise. The development is always iterative, including several loops of material synthesis, testing, and modifications based on the evalua- tion. The research behind the present thesis encompasses work with coating synthesis and tribological testing and evaluation based on a solid knowledge about the inner structure and composition of the materials. By employing advanced surface analysis and high-resolution microscopy, the materials development and tribological evaluation processes are made much more efficient. Moreover, this evaluation can be performed both on the as-synthesised material and after tribological testing or practical use. Knowl- edge on how the material interacts on the atomic scale with the counter sur- faces, provides even more information and gives hints on how to make the materials even better suited to performing their intended tasks. I.1.1 Tribology Tribology covers the science and technology of surfaces in contact and rela- tive motion. This broad definition makes it extremely common and hence an important field of study. It includes friction, wear and lubrication and associ- ated surface layers on the contacting bodies1. Tribology is also of great eco- nomic significance in all industrial sectors. In late years this has been espe- cially evident in the development and use of tools, machine components and vehicles to meet today’s increasing economical and environmental restric- tions. 11 Surfaces in tribological contact are subject to very harsh environments characterized by extreme local pressures, temperatures and deformation. Under these conditions, surface films are formed through reactions between the contacting materials and the surrounding atmosphere or lubricant, but also through phase changes resulting in a surface layer with different proper- ties compared to the original surface. These surface films, often referred to as tribofilms, may be very thin i.e. from a couple of nanometers to a few micrometers. Despite their insignificant thickness they will govern the be- haviour of critical tribological components. Obviously, the study of tri- bofilms or related material properties requires high resolving power which is provided by techniques such as Auger electron spectroscopy (AES), trans- mission electron microscopy (TEM), scanning electron microscopy (SEM) or atom force microscopy (AFM), among others. I.1.2 Surface Modification Low friction films have been used by humans for a very long time and yet there are areas of applications which just recently started to benefit from the advantages of surface modification or coating technology. The ancient Egyp- tians, for instance, used wooden sledges to drag the large stones used to build the pyramids. The sledge was dragged on a wooden track and recov- ered wall paintings reveal that a lubricant, probably water, was used to alter the surface properties and reduce the friction. This early documented use of friction-reduction technology shows that man has addressed this problem for a long time, and that the use of lubricants and oils today bear a close resem- blance with the use then. However, in vacuum technology, space applica- tions or food industry, where there is a need for low friction components, one cannot make use of liquid lubricants. In the case of vacuum technology and space applications it is difficult to keep the lubricants in position due to the low pressure2-4, and in the food industry a lubricant might contaminate the food5. To solve this problem, solid low-friction materials have been de- veloped and used successfully. Today, thin layers of solid lubricants are used to reduce friction and wear in many applications with sliding contacts such as on video tapes, computer hard disks and reader heads6. The great economic significance of tribological
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