Tribological Effects of BN and MoS₂ Nanoparticles Added to Polyalphaolefin Oil in Piston Skirt/Cylinder Liner Tests

In this work, the friction and wear of poly-alpha-olefin (PAO10) base oil with 3 wt. % boron nitride (BN), and molybdenum disulfide (MoS₂) nanoparticles were studied. The formulations were tested using cast iron cylinder-liner segments reciprocating against aluminum alloy piston-skirt segments at 20, 40, and 100°C. The results showed that at a load of 250 N and reciprocating frequency of 2 Hz BN did not lower friction, whereas MoS₂ nanoparticles were very effective at reducing both friction and wear, compared to the base oil. Raman spectroscopy showed the formation of an aligned MoS₂ layer on the cast iron liner surface, which functioned as a tribofilm. In the case of the cast iron liner tested with BN nanolubricant there were no traces of BN that could be related to tribofilm formation. The effect of surfactant was also studied and it was found that not only it was beneficial in dispersing the nanoparticles in oil, but also produced some reduction in friction and wear even as stand-alone additive in PAO10.