| In order to improve the tribological performance of the aluminium-steel contact, two research lines have been followed: (1) Use of the ordered fluids liquid crystals and ionic liquids as lubricant additives. (2) Tribological behaviour of new powder metallurgy aluminium materials processed by mechanical milling.; A parafinic-naftenic base oil modified by a 1wt% of four additives has been used: Three liquid crystals with increasing polarity: 4,4' -dibutylazobenzene (LC1) < colesteryl linoleate (LC2) < n-dodecyl ammonium chloride (LC3), and the ionic liquid 1-ethyl, 3-methyl-imidazolonium tetrafluoroborate. This is the first time that a ionic liquid is studied as lubricant additive.; Viscosity measurements at 25 and 100°C, maximum number of molecules by unit aluminium surface and comparative costs of the additives showed the advantage of the ionic additives over the neutral ones.; Pin-on-disk tests were performed according to ASTM G99. Influence of load, speed and temperature on friction and wear was studied for each additive.; While the ionic liquid gives low friction (<0.1) and wear (≤10-5 mm3m-1), the performance of the liquid crystalline additives depends on the conditions. LC3 shows a higher lubricating ability than the neutral LC1 and LC2 under high load, speed or temperature.; Only the ionic liquid shows tribochemical interaction (by SEM and EDS) with the steel and aluminium surfaces, with an increment in the fluorine content inside the wear track.; The second line was to study the influence of the process conditions on the dry and lubricated wear of new powder-metallurgy aluminium materials.; MA Al-NH3 milled under NH3 atmosphere was compared with (MA Al-Air) processed in air and with Al-1 which has not been mechanically alloyed.; Conditions for mild to severe wear transition have been established. Al-1 is always under a severe wear regime. MA Al-NH3 shows transition to severe wear at 150°C, showing a 60% reduction in wear rate with respect to MA Al-Air and a two order of magnitude reduction with respect to Al-1.; The wear resistance of MA Al-NH3 is attributed to its high hardness, lower porosity, and fine microstructure with submicroscopic reinforcing phases such as aluminium carbide and nitride (by X-ray diffraction and TEM observations). |
