Strengthening mechanism of in-situ synthesized Cu2S nanoparticles on tribological performance of polyamide-imide bonded solid lubricating coatings

Cuprous sulfide (Cu2S) nanoparticles were in-situ synthesized in Polyamide-imide (PAI) bonded solid lubricating coatings to improve the tribological performance of PAI lubricating coatings. To reveal the strengthening mechanism of in-situ synthesized Cu2S nanoparticles on tribological performance of PAI lubricating coatings, hydrothermal synthesized Cu2S (noted as HS-Cu2S) nanoparticles were also prepared as a comparison. The experimental result indicated that in-situ synthesized Cu2S nanoparticles can more conspicuously promote the tribological performance of PAI lubricating coatings than HS-Cu2S nanoparticles. The possible reason was attributed to that in-situ synthesized Cu2S nanoparticles generated interfacial interactions with bonded resin PAI during the high-temperature curing process of composite coatings. As a result, the dispersion performance of in-situ synthesized Cu2S nanoparticles was effectively promoted in PAI lubricating coatings, and simultaneously, the bonding strength between Cu2S nanoparticles and bonded resin was also stimulated. What's more, a continuous organic-inorganic composite tribo-film was in-situ formed on the surface of the counterpart steel ball during the friction process. Therefore, direct abrasion between counterpart steel ball and composite coatings was restrained, and tribological performance of the composite coatings was significantly promoted.