Tribological behaviour of aluminium alloy AA7075 after ion implantation

The present paper reports the effect of nitrogen and molybdenum implantations in the tribological properties of aluminium alloy AA7075 with different heat treatments of structural hardening (T6 and T73).Nanoindentation tests have been performed in order to study the hardness of the implanted layer, which was previously characterized by XPS and GAXRD. The study of the dry sliding wear behaviour has been done using a pin-on-disk tester and complemented with the analysis of the wear tracks by SEM/EDS and interferometric measurements.Our results show that nitrogen implantation is more effective than molybdenum implantation is the selected conditions (2 × 1017 N+ ions/cm2, 50 keV and 2 × 1016 Mo+ ions/cm2, 100 keV respectively). The formation of a modified layer containing a nitride phase, AlN, can explain the noticeable improvement on hardness and wear resistance observed in the nitrogen implanted samples, where the specific wear rate is reduced between 60 and 75% depending on the temper of the alloy. However, Mo+ implantation that does not induce the formation of any new phase produces a minor hardness improvement and reduces the specific wear rate to a lesser extent (about 30–45%).Finally, the study of the wear tracks allows us to conclude that the adhesive-abrasive mechanism, which is the dominant wear mechanism in the unimplanted alloys, is not modified by the implantation process.

► N and Mo implantations clearly improved tribological properties of AA7075.
► N+ implantation is more effective due to the formation of AlN layer.
► Improved surface properties after Mo+ implantation are due to damage by ion bombardment.
► The effect of implantations is highly dependent on temper: more effective in T73.