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Nanoindentation on micro pillars for determination of intrincic hardness and residual stress in coatings deposited on complex geometries
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
(English)Manuscript (preprint) (Other academic)
Keyword [en]
nanoindentation, hardness, residual stress, focused ion beam, coating, PVD
National Category
Materials Engineering Other Materials Engineering
Research subject
Materials Science; Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-160807OAI: oai:DiVA.org:uu-160807DiVA: diva2:453056
Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2016-04-22
In thesis
1. Nanocomposites for Use in Sliding Electrical Contacts
Open this publication in new window or tab >>Nanocomposites for Use in Sliding Electrical Contacts
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis nanocomposite materials for use in high performance electrical contacts are tested. Self mating silver as coatings on cupper substrates are the most used material combination in power connectors today. In this work two new concepts were tested. The first one was to change one of the mating surfaces to a hard thin coating and keep the other surface made of silver. Tested coatings were nanocomposites with hard carbides in a matrix of amorphous carbon. TiC/a-C and  Ti-Ni-C/a-C were tested both electrically and tribologically. The total amount of carbon and the amount of carbon matrix was important, both for the electrical and the tribological properties. The Ti-Ni-C coating also showed that substituting Ti in TiC with the weak carbide former Ni changed the stability of the carbides. The substitution resulted in more a-C matrix and less C in the carbides. Thin coatings of nc-TiC/a-C and  Ti-Ni-C/a-C showed high potential as material candidates for use in electrical contacts.

The other tested concept was to modify the used silver instead of replacing it. This was done by embedding nanoparticles of solid lubricant IF-WS2 in the silver. The results from reciprocating sliding displayed low friction and high wear resistance. The modified silver surfaces lasted for 8000 strokes with a friction of about 0.3 while at the same time allowing for a low contact resistance. The results for surfaces of pure silver coating displayed a friction of 0.8-1.2 and that the silver was worn through already after 300 strokes.

A new method to investigate inherent hardness and residual stress of thin coatings, on complex geometries or in small areas, was also developed. An ion beam was used to create stress free coating as free standing micro pillars. Hardness measured on the pillars and on as-deposited coating were then used to calculate the residual stress in the coatings.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 879
Keyword
tribology, materials science
National Category
Materials Engineering Other Materials Engineering Composite Science and Engineering
Research subject
Materials Science; Engineering Science with specialization in Materials Science; Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-160809 (URN)978-91-554-8219-0 (ISBN)
Public defence
2011-12-09, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2011-11-18 Created: 2011-11-01 Last updated: 2011-11-23Bibliographically approved

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Wiklund, Urban

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