Lubricating greases are widely used in several heavily loaded tribopairs such as rolling element bearings, gears, chains, etc. Each application represents its own unique load/speed/temperature operating condition that the grease needs to be designed to. Since the non-conforming surfaces are elastically deformed and the pressure involved sufficiently high to give significant effects on viscosity the prevailing lubrication mechanism in grease lubricated pairs is elastohydrodynamic (EHL). However, under more severe loading case and low speeds in transient operation a boundary lubrication component may appear, i.e. when metal surfaces actually come into direct contact with no fluid layer between. The additive formulations of greases integrate a substantial degree of components that reduce wear in boundary conditions. Different types and combinations of thickeners and base oils, along with supplemental structure modifiers and performance additives, combine to give the end user product its special lubricating properties. In this paper the performances of nano-formulated grease through inorganic based additives were tested. In particular, one-pot syntheses was used to obtain free-floating nanosheets of tungsten and/or molybdenum disulphide functionalized by long chain amines in the form of fluid suspension or solid paste. The nanosheets obtained are constituted by one or few layers of crystalline metal chalcogenides completely covered by an organic coating. With respect to similar inorganic materials, the presence of coating stabilizes the suspension, avoids aggregation and oxidation phenomena. The nano-materials, successfully tested in base lubricating oils, were dispersed in the lubricating greases and compared by rheological and tribological tests to the conventional lubricating greases.

TRIBOLOGICAL AND RHEOLOGICAL BEHAVIOUR OF LUBRICATING GREASES WITH NANOSIZED INORGANIC BASED ADDITIVES

ALTAVILLA, CLAUDIA;CIAMBELLI, Paolo;SARNO, Maria;NOBILE, Maria Rossella;SOMMA, Elvira;D'AGOSTINO, Vincenzo;SENATORE, ADOLFO;PETRONE, VINCENZO
2011-01-01

Abstract

Lubricating greases are widely used in several heavily loaded tribopairs such as rolling element bearings, gears, chains, etc. Each application represents its own unique load/speed/temperature operating condition that the grease needs to be designed to. Since the non-conforming surfaces are elastically deformed and the pressure involved sufficiently high to give significant effects on viscosity the prevailing lubrication mechanism in grease lubricated pairs is elastohydrodynamic (EHL). However, under more severe loading case and low speeds in transient operation a boundary lubrication component may appear, i.e. when metal surfaces actually come into direct contact with no fluid layer between. The additive formulations of greases integrate a substantial degree of components that reduce wear in boundary conditions. Different types and combinations of thickeners and base oils, along with supplemental structure modifiers and performance additives, combine to give the end user product its special lubricating properties. In this paper the performances of nano-formulated grease through inorganic based additives were tested. In particular, one-pot syntheses was used to obtain free-floating nanosheets of tungsten and/or molybdenum disulphide functionalized by long chain amines in the form of fluid suspension or solid paste. The nanosheets obtained are constituted by one or few layers of crystalline metal chalcogenides completely covered by an organic coating. With respect to similar inorganic materials, the presence of coating stabilizes the suspension, avoids aggregation and oxidation phenomena. The nano-materials, successfully tested in base lubricating oils, were dispersed in the lubricating greases and compared by rheological and tribological tests to the conventional lubricating greases.
2011
9783901657399
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/3024624
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