Relations between low frictional property in fullerene-added oil and surface roughness parameters

Abstract

This study aimed to reduce friction of the internal parts of an engine such as a vehicle by using fullerene (FLN) -added lubrication oil. We investigated the friction characteristics of it with the change of surface roughness under boundary lubrication to improve fuel efficiency. We produced the test specimens with plateau structure and surface roughness Ra=0.1~2.6 with various roughness parameters using sandpaper and used a ball on plate tester. The specimens is SUJ2 and the used oil is PAO4 and PAO4 added 1000 ppm mix-fullerene. We measured fifteen roughness parameters (Rp, Rv, Rz, Ra, Rq, Rsk, Rku, Rsm, RΔq, R𝛿c, Rk, Rpk, Rvk, Mr1, Mr2) of the specimen surfaces and elucidated the relation between these parameters and the friction coefficients for fullerene-added oil. The results showed that the relation between three parameters (Rsk, Rp, RΔq) and them can be approximated by quadratic function and all the determination coefficients are more than 0.8. PLS regression analysis revealed a linear relationship (R²=0.72) between these 15 roughness parameters and the friction coefficient in the fullerene-added oil, which means that the friction coefficient can be controlled by manipulating the surface profiles by adding fullerenes. The difference in friction properties between the base oil and the fullerene-added oil was suggested to be the effect of spinnability.