Performance of graphite and boron-nitride-silicone based lubricants and associated lubrication mechanisms in warm forging of aluminum / Gracious Ngaile in Transactions of the ASME . Journal of tribology, Vol. 130 n°2 (Mars/Avril 2008)  

Public ISBD [article]  inTransactions of the ASME . Journal of tribology > Vol. 130 n°2 (Mars/Avril 2008) . - 7 p. Titre : Performance of graphite and boron-nitride-silicone based lubricants and associated lubrication mechanisms in warm forging of aluminum Type de document : texte imprimé Auteurs : Gracious Ngaile, Auteur ; Frank Botz, Auteur Année de publication : 2008 Article en page(s) : 7 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Water/oil-graphite emulsions Graphite-based lubricants Boron-nitride-silicone Résumé : Although water/oil-graphite emulsions are widely used in warm forging processes, they carry environmental concerns. In an attempt to replace graphite-based lubricants in warm forging of aluminum alloys, two variants of boron-nitride-silicone lubricants were formulated. The two variants were made by dispersing boron nitride powder in polydimethyl siloxane oil at concentrations of 1% and 8%. The formulated lubricants were initially tested for their thermal degradation characteristics using a thermogravimetric analyzer and compared to the thermal degradation behavior of graphite and silicone oil lubricants. Ring compression tests were then carried out at 260°C and 370°C. Boron-nitride-silicone lubricant variants did not show significant difference in performance as die temperature was increased from 260°Cto370°C. This is in contrast to graphite, which performed much better at 260°C than at 370°C, due to thermal oxidation. On the other hand, silicone oil exhibited the worst performance at 260°C and the best performance at 370°C. In both boron nitride lubricant variants, the polydimethyl siloxane facilitated hydrostatic/hydrodynamic lubrication at 260°C, with boron nitride acting as a barrier film that reduced friction. However, the lubrication mechanisms changed at 370°C, where the depolymerization of polydimethyl siloxane led to formation of silica due to thermal oxidation. Silica, together with boron nitride, acted as a film barrier with low shear strength. The dual lubrication mechanisms make boron-nitride-silicone lubricants suitable for a wide range of aluminum forging temperatures. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleid=1468033 [article] Performance of graphite and boron-nitride-silicone based lubricants and associated lubrication mechanisms in warm forging of aluminum [texte imprimé] / Gracious Ngaile, Auteur ; Frank Botz, Auteur . - 2008 . - 7 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 130 n°2 (Mars/Avril 2008) . - 7 p. Mots-clés : Water/oil-graphite emulsions Graphite-based lubricants Boron-nitride-silicone Résumé : Although water/oil-graphite emulsions are widely used in warm forging processes, they carry environmental concerns. In an attempt to replace graphite-based lubricants in warm forging of aluminum alloys, two variants of boron-nitride-silicone lubricants were formulated. The two variants were made by dispersing boron nitride powder in polydimethyl siloxane oil at concentrations of 1% and 8%. The formulated lubricants were initially tested for their thermal degradation characteristics using a thermogravimetric analyzer and compared to the thermal degradation behavior of graphite and silicone oil lubricants. Ring compression tests were then carried out at 260°C and 370°C. Boron-nitride-silicone lubricant variants did not show significant difference in performance as die temperature was increased from 260°Cto370°C. This is in contrast to graphite, which performed much better at 260°C than at 370°C, due to thermal oxidation. On the other hand, silicone oil exhibited the worst performance at 260°C and the best performance at 370°C. In both boron nitride lubricant variants, the polydimethyl siloxane facilitated hydrostatic/hydrodynamic lubrication at 260°C, with boron nitride acting as a barrier film that reduced friction. However, the lubrication mechanisms changed at 370°C, where the depolymerization of polydimethyl siloxane led to formation of silica due to thermal oxidation. Silica, together with boron nitride, acted as a film barrier with low shear strength. The dual lubrication mechanisms make boron-nitride-silicone lubricants suitable for a wide range of aluminum forging temperatures. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleid=1468033

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