Combination of nanoparticles of graphite and hexagonal boron nitride as anti-wear and extreme-pressure additives- On exploring the possibility of synergism

Nano-particles (NPs) are extensively explored as additives (anti-friction- AF, anti-wear AW and extreme pressure- EP) in oils and greases. Combinations of NPs of graphite and hexagonal boron nitride (hBN) were tried in Group III oil keeping total amount constant (4 wt.%) along with dispersant (Polyisobutylene succinimide -PIBSI- 1 wt. %) to explore the possible synergism in AW and EP performance. Combo-oils with 2 % of each NPs showed synergistic effect in AW performance with 63% improvement compared to the parent oil. The SEM and EDAX studies on ball surface worn in this oil revealed best quality film (smooth, thin and coherent) and also with lowest roughness of 56 nm as confirmed from the atomic force microscopy (AFM). In case of EP test, however, no synergism was observed. Graphite NPs (4 %) proved most effective with 78% improvement. Step-wise inclusion of hBN deteriorated the performance.