Synergistic Effects of MoDTC and ZDTP on Frictional Behaviour of Tribofilms at the Nanometer Scale

The layered structure and the rheological properties of anti-wear films, generated in a rolling/sliding contact from lubricants containing zinc dialkyldithiophosphate (ZDTP) and/or molybdenum dialkyldithiocarbamate (MoDTC) additives, have been studied by dynamic nanoindentation experiments coupled w...

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Bibliographic Details
Published in:Tribology letters 2004-11, Vol.17 (4), p.797-809
Main Authors: Bec, S., Tonck, A., Georges, J. M., Roper, G. W.
Format: Article
Language:English
Subjects:
Additives
Coefficient of friction
Condensed Matter
Engineering Sciences
Formulations
Friction
Lubricants
Lubricants & lubrication
Materials Science
Mechanics
Mechanics of materials
Molybdenum disulfide
Nanoindentation
Physics
Rheological properties
Sliding contact
Stiffness
Tribology
Zinc dialkyldithiophosphates
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Summary:The layered structure and the rheological properties of anti-wear films, generated in a rolling/sliding contact from lubricants containing zinc dialkyldithiophosphate (ZDTP) and/or molybdenum dialkyldithiocarbamate (MoDTC) additives, have been studied by dynamic nanoindentation experiments coupled with a simple modelling of the stiffness measurements. Local nano-friction experiments were conducted with the same device in order to determine the evolution of the friction coefficient as a function of the applied pressure for the different lubricant formulations. For the MoDTC film, the applied pressure in the friction test remains low ( 0.4). For the tribofilms containing MoDTC together with ZDTP, which permits the applied pressure to increase up to a few GPa through some accommodation process, a very low friction domain appears (0.01 < μ < 0.05), located a few nanometers below the surface of the tribofilm. This low friction coefficient is attributed to the presence of MoS2 planes sliding over each other in a favourable configuration obtained when the pressure is sufficiently high, which is made possible by the presence of ZDTP.
ISSN:1023-8883
1573-2711
DOI:10.1007/s11249-004-8088-7