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Scuffing resistance testing of piston ring materials for marine two-stroke diesel engines and mapping of the operating mechanisms
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.
2015 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 330, p. 42-48Article in journal (Refereed) Published
Abstract [en]

The incentive is strong for optimising sliding materials to reduce the risk for scuffing. In this study, scuffing tests were performed aiming towards finding new piston ring materials for greener marine diesel engines and also towards understanding scuffing mechanisms better. The tested ring materials where grey iron, Stellite 6, plasma sprayed cermet and high velocity oxy fuel (HVOF) cermet (both cermets with the same compounds: Cr-carbide, Ni, Cr, Mo). The Stellite 6 and HVOF cermet performed somewhat better than the other two materials. Microscopic and spectroscopic studies of failed sample surfaces revealed several characteristic features. It was clear that different mechanisms are active simultaneously, at different parts of the samples. Based on these results, we propose a hypothesis for a scuffing process involving several stages with distinctive mechanisms. Further studies are needed to strengthen this hypothesis and to relate these findings to actual deterioration mechanisms in the engine.

Place, publisher, year, edition, pages
2015. Vol. 330, p. 42-48
Keyword [en]
Scuffing, Boundary lubrication, Marine diesel engines, Cast iron, Cermet, Stellite
National Category
Materials Engineering Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
URN: urn:nbn:se:uu:diva-260160DOI: 10.1016/j.wear.2015.01.074ISI: 000357438000006OAI: oai:DiVA.org:uu-260160DiVA, id: diva2:846590
Funder
EU, FP7, Seventh Framework Programme, 265861
Available from: 2015-08-17 Created: 2015-08-17 Last updated: 2018-01-11Bibliographically approved
In thesis
1. Tribology for Greener Combustion Engines: Scuffing in Marine Engines and a Lubricating Boric Acid Fuel Additive
Open this publication in new window or tab >>Tribology for Greener Combustion Engines: Scuffing in Marine Engines and a Lubricating Boric Acid Fuel Additive
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Tribologi för grönare förbränningsmotorer : Skuffning i fartygsmotorer och ett smörjande borsyrabaserat bränsleadditiv
Abstract [en]

This thesis aims at increased knowledge in two fields of tribological research; both related to making currently used combustion engines greener. The first field regards the possibilities of using a boric acid fuel additive to increase fuel efficiency. The second field is about the severe wear phenomenon scuffing, which can become problematic when cargo ships are operated on low-sulphur fuel to reduce sulphuric emissions.

Tribological tests were developed and performed to simulate the applications. Advanced surface analysis was performed to understand changes occurring on the outermost surface of sliding components, which affect friction and wear. Samples from engines were studied to verify the relation between the lab tests and the applications.

In the case of boric acid, the coefficient of friction was below 0.02 for large parts of the tests, but varied with test parameters. The corresponding reduction in friction was up to 78% compared with tests without the additive. As an attempt to assess if the substantial fuel savings found in field tests with passenger cars (6%) can be explained by friction reduction in boundary and mixed lubricated parts of the piston assembly, assumptions were presented that would lead to fuel savings close to these 6%. Boric acid was detected on surfaces after the tests, and the tribofilm appearance depended on test parameters. The tribofilms were shown to be affected by storage time and test temperature; a finding that is vital for future studies.

In the case of scuffing, mechanisms were studied and accumulation of wear debris had a significant role on scuffing initiation in the lab scale scuffing tests. Regarding the possibility to test materials scuffing resistance, there was a large scatter in the results, and thereby difficult to draw conclusions. Two new piston ring materials were identified to perform somewhat better than the currently used.

In conclusion, findings that could facilitate immediate improvement of fuel efficiency of today’s combustion engine vehicles as well as findings that strengthen available hypotheses on scuffing mechanisms are presented. The latter offers improved understanding of scuffing and thereby give possibilities to counteract the higher risk associated with operation on cleaner fuel.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 97
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1607
Keyword
Friction, wear, lubrication, energy loss, atmospheric emissions, fuel efficiency, transport.
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Other Materials Engineering
Research subject
Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-333430 (URN)978-91-513-0174-7 (ISBN)
Public defence
2018-01-19, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2017-12-21 Created: 2017-11-29 Last updated: 2018-03-08

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Olander, PetraJacobson, Staffan

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