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Your search keyword '"Hogmark, Sture"' showing total 48 results
Start Over Author "Hogmark, Sture" Publisher uppsala universitet, materialvetenskap
48 results on '"Hogmark, Sture"'

1. An atomistic approach to the initiation mechanism of galling

Author

Vitos, Levente, Larsson, Karin, Johansson, Börje, Hanson, Magnus, Hogmark, Sture, Vitos, Levente, Larsson, Karin, Johansson, Börje, Hanson, Magnus, and Hogmark, Sture

Abstract

Sliding metallic contacts are accompanied by a severe wear phenomenon named galling. This is manifested in adhesion followed by a substantial increase of friction and subsequent deterioration of the contact surfaces. Experiments on titanium- and vanadium-nitride coated surfaces slid against steels indicate that VN exhibits low friction and improved galling characteristics, clearly outperforming the widely used TiN coating. Using first principles simulations, based on the exact muffin-tin orbital and pseudopotential methods, we present an insight to the atomic level processes initiating galling at Ti(V)N-Fe interfaces. It is found that the equilibrium atomic-scale contacts between nitrides and Fe are adhesive. We demonstrate that the close-packed (001) VN-Fe interface exhibits a lower atomic-level roughness and a reduced atomic-friction coefficient than that in the case of TiN. These theoretical results indicate that VN is less prone to galling compared to TiN.

Published
2006
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2. Surface analysis of laser cladded Stellite exposed to self-mated high load dry sliding

Author

Persson, Daniel H. E., Coronel, Ernesto, Jacobson, Staffan, Hogmark, Sture, Persson, Daniel H. E., Coronel, Ernesto, Jacobson, Staffan, and Hogmark, Sture

Abstract

Materials from the Stellite family of Co-based alloys are commonly used as low friction, galling resistant materials in high load dry sliding contact applications. In the present investigation, the surface region of a Co-based material (Stellite 21) exposed to self-mated high load dry sliding at room temperature has been analysed in detail. During sliding, an approximately 30 nm thick Co-enriched tribofilm is created. It exhibits low friction properties and a high galling resistance. The transformation from an face-centred-cubic structure to easily sheared hexagonal-closed-packed basal planes in the tribofilm combined with the high load carrying capacity of the underlying deformation hardened zone is suggested to explain the excellent low friction properties and galling resistance of this material.

Published
2006
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3. On the effect of surface topography and humidity on lubricated running-in of a carbon based coating

Author

Svahn, Fredrik, Kassman-Rudolphi, Åsa, Hogmark, Sture, Svahn, Fredrik, Kassman-Rudolphi, Åsa, and Hogmark, Sture

Abstract

The running-in behaviour of an amorphous carbon coating has been evaluated with respect to the substrate surface topography and the humidity of the surrounding environment. Four different surface treatments: polishing, grinding, wet-sandblasting and sandblasting, were employed prior to coating deposition. Sliding ball-on-disc tests were made in dry and humid air with four different oils: one PAO, one ester, one paraffinic mineral oil (all non-additivated) and one fully formulated mineral based engine oil. It was found that wet-blasted surfaces, having an Rq-value of 0.2 μm but much sharper asperities than typically ground surfaces, gave the coatings a better running-in ability compared with the other surfaces. The friction reduced rapidly from typical boundary lubricated values (0.09) to typical values of mixed boundary and EHL lubrication (0.04-0.045), without excessive wear of the steel counter body. No coating delamination was observed for coatings on this surface, and the mild wear was a fine polishing. This running-in behaviour was only observed in dry environments and only with non-additivated and non-polar oils, with PAO giving the lowest friction. In air of 50-60% relative humidity, no transition from boundary to EHL or mixed lubrication could be observed. For all oils and all surface topographies, the friction was always constant at levels typical for boundary lubrication. In dry air a thick tribo-layer composed of oxide was formed on the steel counter body but not in humid air. This oxide, along with a fine polishing of the surfaces and a macroscopic pressure reduction due to wear of the counter body, is believed to be important for the running-in ability.

Published
2006
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4. Editorial

Author

Hogmark, Sture, Jacobson, Staffan, Hogmark, Sture, and Jacobson, Staffan

Published
2006

14. Interactive Tribological Coatings

Author

Hogmark, Sture, Nilsson, Daniel, Svahn, Fredrik, Ignberg, L, Hogmark, Sture, Nilsson, Daniel, Svahn, Fredrik, and Ignberg, L

Published
2004

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