Improving the tribological properties of NiAl matrix composites via hybrid lubricants of silver and graphene nano platelets

This work presents a comprehensive study of the synergistic tribological effect of combined solid lubricants of silver and graphene nano platelets (GNPs). Moreover, it presents a comparative study of the tribological characteristics of NiAl (NA), NiAl-10 wt% silver (NAS), NiAl-1.5 wt% GNPs (NAG), NiAl-1.5 wt% GNPs-10 wt% silver (NAGS10) and NiAl-1.5 wt% GNPs-15 wt% silver (NAGS15) composites based on tribological and microstructural tests. The NAGS10 composite shows the lowest friction coefficients and the highest wear resistance among the whole composites at different sliding velocities and applied loads, while NA exhibits the highest friction coefficients and wear rates at the same sliding conditions. The microstructural tests of NAGS10 and NAGS15 composites reveal the formation of GNPs and silver enriched islands which act as the bearing areas and play the major role in loading transition. Furthermore, those islands ease the slipping of the graphene layers over the NiAl substrate.