Extreme friction reductions during inital running-in of W-S-C-Ti low-friction coatings
2013 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 302, no 1-2 SI, 987-997 p.Article in journal (Refereed) Published
The disulphides of tungsten and molybdenum are known for their low friction properties when used as solid lubricants. Due to their low hardness, their load bearing capacity when used as thin films is poor. When carbon is added to a WS2 coating, both of these shortcomings are improved, and a structure consisting of nanocrystals of WS2, and possibly tungsten carbide, in a matrix of amorphous carbon is formed. In this study, an attempt is made for further increasing the hardness of such coatings, by addition of Ti, a strong carbide former. A number of W–S–C(–Ti) coatings were deposited using magnetron co-sputtering, and characterised with regard to chemical composition, structure and tribological properties. It was seen that addition of Ti significantly increased the hardness of the coatings, while maintaining their excellent low friction properties in dry atmosphere. However, the coatings with Ti showed extremely high initial friction, a feature not seen for the coatings without Ti. The mechanisms behind this running-in behaviour were investigated by studying surfaces at early stages of wear. It was observed that tribofilms formed during sliding for the coatings containing Ti consisted mainly of TiO2, with platelets of WS2 appearing in the contact only after prolonged sliding. For the pure W–S–C coatings, WS2 was observed in the sliding interface almost instantly at the onset of sliding.
Place, publisher, year, edition, pages
Elsevier, 2013. Vol. 302, no 1-2 SI, 987-997 p.
Nano Technology Tribology
Research subject Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science; Engineering Science with specialization in Electronics
IdentifiersURN: urn:nbn:se:uu:diva-191211DOI: 10.1016/j.wear.2013.01.065ISI: 000322682800018OAI: oai:DiVA.org:uu-191211DiVA: diva2:585056
19th International Conference on Wear of Materials 2013; 14-18 April 2013; Portland, OR, USA
FunderSwedish Foundation for Strategic Research