Friction and wear behavior of nanosilica-filled epoxy resin composite coatings

Hydrophilic silica nanoparticles (abridged as nano-SiO2) surface-capped with epoxide were dispersed in the solution of epoxy resin (abridged as EP) in tetrahydrofuran under magnetic stirring. Resultant suspension of nano-SiO2 in EP was then coated onto the surface of glass slides and dried at 80 °C in a vacuum oven for 2 h, generating epoxy resin-nanosilica composite coatings (coded as EP/nano-SiO2). EP coating without nano-SiO2 was also prepared as a reference in the same manner. A water contact angle meter and a surface profiler were separately performed to measure the water contact angles and surface roughness of as-prepared EP/nano-SiO2 composite coatings. The friction and wear behavior of as-prepared EP/nano-SiO2 composite coatings sliding against steel in a ball-on-plate contact configuration under unlubricated condition was evaluated. Particularly, the effect of coating composition on the friction and wear behavior of the composite coatings was highlighted in relation to their microstructure and worn surface morphology examined by means of scanning electron microscopy. Results indicate that EP/nano-SiO2 composite coatings have a higher surface roughness and water contact angle than EP coating. The EP-SiO2 coatings doped with a proper amount of hydrophilic SiO2 nanoparticles show lower friction coefficient than EP coating. However, the introduction of surface-capped nanosilica as the filler results in inconsistent change in the friction coefficient and wear rate of the filled EP-matrix composites; and it needs further study to achieve well balanced friction-reducing and antiwear abilities of the composite coatings for tribological applications.