Characterization and auto-restoration mechanism of nanoscale serpentine powder as lubricating oil additive under high temperature

Friction and wear experiments were carried out with nanoscale serpentine (a magnesium silicate mineral) and heat-treated serpentine as lubricating oil additives at 400 °C. The tribological test results showed that the self-repairing protective layers could be well formed on the contact surfaces, whether nanoscale serpentine or heat-treated serpentine powder was added into lubricating oil. SEM and EDAX analysis demonstrate that the morphology and elements of self-repairing layers are in accordance with that of serpentine. A generation mechanism of the layer was proposed from the view of isomorphic replacement theory in mineralogy and petrology, and friction-induced chemical reaction.

Research highlights
► Self-repairing layers were found on the worn surfaces under high temperature.
► Hydroxyl and Hydroxyl water have no influence on self-repairing behaviors.
► Friction chemical reaction and isomorphic replacement were dominant mechanism.