Self-repairing Performance and Formation Mechanism of Self-repairing Layer of Natural Serpentine Powder as a Lubricating Oil Additive

A RFT-III reciprocating friction and wear tester (pin-on-block contact mode) was used to investigate the self-repairing performance of oleic acid-surface-capped natural serpentine powder as a lubricating oil additive for steel-steel frictional pair. The microhardness of worn block surface was measured using a hardness meter. The morphology, elemental composition, and chemical state of typical elements on worn steel surfaces and cross-sections were analyzed by means of scanning electron microscopy, energy dispersive spectrometry; and the self-repairing mechanism of the surface-capped natural serpentine powder was explored. Results indicate that the surface-capped natural serpentine powder as a lubricating oil additive can greatly reduce the friction coefficient and wear rate of the steel-steel pair, which was attributed to the formation of a self-repairing layer with good friction-reducing and antiwear performance on worn steel surface viatribochemical reaction in the presence of the lubricating oil additive. The self-repairing layer was composed of densely packed nanoparticles with various sizes. It contained a large amount of Fe₂O₃ and amorphous graphite as well as a small amount of Fe, organic fragments, Si-containing organic compounds, and SiO₂.