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Growth and characterization of chromium carbide films deposited by high rate reactive magnetron sputtering for electrical contact applications
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0002-5516-6388
Impact Coatings AB, Sweden.
Impact Coatings AB, Sweden.
Impact Coatings AB, Sweden.
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2014 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 260, 326-334 p.Article in journal (Refereed) Published
Abstract [en]

Chromium carbide films with different phase contents were deposited at 126±26 °C by industrial high rate reactivemagnetron sputtering, using both direct current magnetron sputtering (DCMS) and high power impulsemagnetron sputtering (HiPIMS). Film structure and properties were studied by SEM, XRD, TEM, XPS, NRA, Raman spectroscopy, nanoindentation, unlubricated reciprocating sliding experiments, and a laboratory setup to measure electrical contact resistance. The films consisted of amorphous a-CrCy, a nanocrystalline minority phase of metastable cubic nc-CrCx, and a hydrogenated graphite-like amorphous carbon matrix (a-C:H). The DCMS and HiPIMS processes yielded films with similar phase contents and microstructures, as well as similar functional properties. Low elastic modulus, down to 66 GPa, indicated good wear properties via a hardness/elastic modulus (H/E) ratio of 0.087. Unlubricated steady-state friction coefficients down to 0.13 were obtained for films with 69 at.% carbon, while the electrical contact resistance could be reduced by two orders of magnitude by addition of a-C:H phase to purely carbidic films. The present films are promising candidates for sliding electrical contact applications.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 260, 326-334 p.
Keyword [en]
Direct current magnetron sputtering, High power impulse magnetron sputtering, Reactive sputtering, Amorphous chromium carbide, Solid lubricant, Contact resistance
National Category
Physical Chemistry Condensed Matter Physics Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-240742DOI: 10.1016/j.surfcoat.2014.06.069ISI: 000347584300045OAI: oai:DiVA.org:uu-240742DiVA: diva2:777044
Conference
The 41st International Conference on Metallurgical Coatings and Thin Films, APR 28-MAY 02, 2014, San Diego, CA
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2016-08-29Bibliographically approved
In thesis
1. Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts
Open this publication in new window or tab >>Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today’s electronic society relies on the functionality of electrical contacts. To achieve good contact properties, surface coatings are normally applied. Such coatings should ideally fulfill a combination of different properties, like high electrical conductivity, high corrosion resistance, high wear resistance and low cost. A common coating strategy is to use noble metals since these do not form insulating surface oxides. However, such coatings are expensive, have poor wear resistance and they are often applied by electroplating, which poses environmental and human health hazards.

In this thesis, nanocomposite carbide-based coatings were studied and the aim was to evaluate if they could exhibit properties that were suitable for electrical contacts. Coatings in the Cr-C, Cr-C-Ag and Nb-C systems were deposited by magnetron sputtering using research-based equipment as well as industrial-based equipment designed for high-volume production. To achieve the aim, the microstructure and composition of the coatings were characterized, whereas mechanical, tribological, electrical, electrochemical and optical properties were evaluated. A method to optically measure the amount of carbon was developed.

In the Cr-C system, a variety of deposition conditions were explored and amorphous carbide/amorphous carbon (a-C) nanocomposite coatings could be obtained at substrate temperatures up to 500 °C. The amount of a-C was highly dependent on the total carbon content. By co-sputtering with Ag, coatings comprising an amorphous carbide/carbon matrix, with embedded Ag nanoclusters, were obtained. Large numbers of Ag nanoparticles were also found on the surfaces. In the Nb-C system, nanocrystalline carbide/a-C coatings could be deposited. It was found that the nanocomposite coatings formed very thin passive films, consisting of both oxide and a-C.

The Cr-C coatings exhibited low hardness and low-friction properties. In electrochemical experiments, the Cr-C coatings exhibited high oxidation resistance. For the Cr-C-Ag coatings, the Ag nanoparticles oxidized at much lower potentials than bulk Ag. Overall, electrical contact resistances for optimized samples were close to noble metal references at low contact load. Thus, the studied coatings were found to have properties that make them suitable for electrical contact applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 74 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1417
Keyword
transition metal carbide, amorphous carbon, composite, contact resistance, corrosion, friction, optical properties
National Category
Materials Chemistry Inorganic Chemistry Ceramics Nano Technology Composite Science and Engineering Corrosion Engineering
Identifiers
urn:nbn:se:uu:diva-302063 (URN)978-91-554-9676-0 (ISBN)
Public defence
2016-10-14, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2016-09-22 Created: 2016-08-29 Last updated: 2016-10-11

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Nygren, KristianKassman Rudolphi, ÅsaJansson, Ulf
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