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On the dramatic wear protecting effect of tribofilms on wear of combustion engine valves
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Ångström Tribomaterials Group)ORCID iD: 0000-0003-1274-4974
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Ångström Tribomaterials Group)ORCID iD: 0000-0002-3955-5746
2018 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

Combustion engine valves control the flow of gases into and out of the cylinder. Intake valves open to let air in and exhaust valves open to let exhausts out. In the two other strokes of the four-stroke cycle the flow channels need to be sealed to allow efficient combustion. The enormous amount of operational cycles during the service life of an engine forces the wear rate of the sealing surfaces to be extremely low, despite being subjected to high temperatures and high closing forces. Although not being intentionally lubricated, residues from the engine oil reach the sealing surfaces and form protective tribofilms. These prevent the metal-to-metal contact that would otherwise cause rapid wear.

Here, the detailed mechanism behind the protective action of the tribofilms have been investigated using modern techniques for cross sectioning, both through valve surfaces covered by tribofilms and those where it has become worn off. As long as the tribofilm is covering, no wear of the valves could be detected while as soon as it becomes worn off, large-scale deformation and wear occur.

Broad ion beam polishing combines the non-damaging effect of using focused ion beams to produce cross sections with the possibility of studying larger areas.

Place, publisher, year, edition, pages
2018.
Keywords [en]
Combustion engine valve, Tribofilm, Wear protection, Cross sectioning
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Tribo Materials; Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-393106OAI: oai:DiVA.org:uu-393106DiVA, id: diva2:1351643
Conference
The 18th Nordic Symposium on Tribology - Nordtrib 2018, Uppsala, Sweden, June 18-21, 2018
Available from: 2019-09-16 Created: 2019-09-16 Last updated: 2019-09-16

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