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Load capacity and durability of H-DLC coated hydrodynamic thrust bearings / Said Jahanmir in Transactions of the ASME . Journal of tribology, Vol. 133 N° 3 (Juillet 2011) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 133 N° 3 (Juillet 2011) . - 10 p. Titre : Load capacity and durability of H-DLC coated hydrodynamic thrust bearings Type de document : texte imprimé Auteurs : Said Jahanmir, Auteur ; Andrew Z. Hunsberger, Auteur ; Hooshang Heshmat, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Tribilogy Langues : Anglais (eng) Mots-clés : Coatings  Diamond-like  carbon  Friction  Hydrodynamics  Hydrophilicity  Hydrophobicity  Impact  testing  Machine  bearings  Titanium  alloys  Wear  resistance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Hydrogenated diamondlike carbon (H-DLC) coatings provide excellent wear resistance and low friction for bearing applications. However, the use of such coatings with aqueous lubricants could pose some difficulties due to the hydrophobic nature of the surface. A thrust bearing tribometer was used to compare performance of hydrophilic and hydrophobic surfaces in hydrodynamic lubrication with a mixture of water and glycerol as the lubricant. Hydrophobic surfaces on both runner and bearing were achieved with the deposition of H-DLC films on titanium alloy surfaces. Hydrophilic surfaces were created through modification of H-DLC surface with covalently bonded heparin. Several possible combinations of hydrophobic and hydrophilic surface conditions were used on the bearing and runner surfaces to provide full-wetting, partial-wetting, and half-wetting conditions. The experimental results confirmed that load support is still possible, when the bearing is half-wetted or partially wetted. However, the full-wetted bearing combination (i.e., Reynolds no-slip boundary condition) provided the highest load support. Introduction of slip at the surface resulted in a lower measured torque. Heparin treatment resulted in a lower than expected static friction and friction in full lubrication regime. The durability of coated surfaces was evaluated in a series of start–stop tests and in impact tests. The results confirmed that the coatings are stable and survive the test regiment that exceeded 50 test cycles; whereas the uncoated titanium alloy bearing surfaces were damaged after ten test cycles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] Load capacity and durability of H-DLC coated hydrodynamic thrust bearings [texte imprimé] / Said Jahanmir, Auteur ; Andrew Z. Hunsberger, Auteur ; Hooshang Heshmat, Auteur . - 2012 . - 10 p. Tribilogy Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 133 N° 3 (Juillet 2011) . - 10 p. Mots-clés : Coatings  Diamond-like  carbon  Friction  Hydrodynamics  Hydrophilicity  Hydrophobicity  Impact  testing  Machine  bearings  Titanium  alloys  Wear  resistance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Hydrogenated diamondlike carbon (H-DLC) coatings provide excellent wear resistance and low friction for bearing applications. However, the use of such coatings with aqueous lubricants could pose some difficulties due to the hydrophobic nature of the surface. A thrust bearing tribometer was used to compare performance of hydrophilic and hydrophobic surfaces in hydrodynamic lubrication with a mixture of water and glycerol as the lubricant. Hydrophobic surfaces on both runner and bearing were achieved with the deposition of H-DLC films on titanium alloy surfaces. Hydrophilic surfaces were created through modification of H-DLC surface with covalently bonded heparin. Several possible combinations of hydrophobic and hydrophilic surface conditions were used on the bearing and runner surfaces to provide full-wetting, partial-wetting, and half-wetting conditions. The experimental results confirmed that load support is still possible, when the bearing is half-wetted or partially wetted. However, the full-wetted bearing combination (i.e., Reynolds no-slip boundary condition) provided the highest load support. Introduction of slip at the surface resulted in a lower measured torque. Heparin treatment resulted in a lower than expected static friction and friction in full lubrication regime. The durability of coated surfaces was evaluated in a series of start–stop tests and in impact tests. The results confirmed that the coatings are stable and survive the test regiment that exceeded 50 test cycles; whereas the uncoated titanium alloy bearing surfaces were damaged after ten test cycles. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]