Nanofillers for lubricants in mechanical applications: improved performances in real systems and technological impact
Lorenzo CALABRI (Tec Star)
ABSTRACT
Mechanical applications require always more efficient tribological performances using lubricants with improved properties, with reduced environmental impact and, possibly, long lasting over their life cycle.
Lubricants manufacturers usually add so called EP (Extreme Pressures) or AW (Anti-Wear) organic chemical additives, but this is not always satisfactory from a technical point of view and, furthermore, is limited by some environmental and safety problems. As a matter of fact some of these chemical additives are considered dangerous for workers exposition and prone to be banned from the European community.
In recent years, the use of different kinds of nanoparticles (oxides and onion like) as additives for oils and greases, has been of great interest for the scientific community, but also for direct real applications.
These nanoparticles act as nanoscaled bearings avoiding direct contact between surfaces, even at very high load and at low lubrication condition (boundary lubrication), but this effective result strongly depends upon the uniform dispersion, the stability, and the concentration of the nanoadditives within the lubricant. These three parameters represent the major technological barrier to overcome, in order to use these materials in real industrial settings.
The reduction of the wear rate, and a stabilization in the friction coefficient trend are the first noticeable effects of the use of nanoadditives, but, in some applications, also beneficial effects in the initial transient phase are visible, avoiding friction overshooting related to the initial trial phase (i.e. endless screw with frequent motion reversion) and, thus, allowing to operate in severe conditions.
Along this presentation all these aspects will be explained in light of specific applications in real systems, taking into account different types of oils (mineral, synthetic, ester-based, etc.) and greases, using different kind of nanoparticles (oxides and onion like). Particular attention will be devoted to gear motors, metal working process, traction gearboxes and in general industrial applications.
