Tribological behaviors of an attapulgite–graphene nanocomposite as an additive for mineral lubricating oil

Abstract

In this work, an attapulgite–graphene nanocomposite was prepared. The tribological properties of the prepared attapulgite–graphene nanocomposite as an additive for 200SN mineral lubricating oil were investigated using an SRV-IV tribometer through ball-on-disk contact mode for the first time. The characterization of the prepared nanocomposite indicated that attapulgite nanofibers are enveloped by the graphene nanosheets and present fine combination. The tribological test results show that the friction-reducing and antiwear properties of 200SN were obviously improved by adding the attapulgite–graphene nanocomposite. Through the characterization and analysis of the worn surface and cross-section, it was found that a tribofilm composed of Fe, Fe₃O₄, FeO, Fe₂O₃, FeOOH, graphite, graphene, SiO₂ and organic compounds was formed on the worn surface. Furthermore, the bonding between the tribofilm and steel matrix is tight. The tribofilm and lubricating oil achieve a solid–liquid coupling lubrication effect, which is responsible for the improvement of the friction-reducing and antiwear properties.