Tribochemical aspects of silicon nitride ceramic sliding against stainless steel under the lubrication of seawater

Tribological behaviors of Si3N4 ceramic sliding against 316 stainless steel under seawater lubrication were investigated and compared with those under dry sliding and pure water lubrication. The results showed that SiO2 colloidal particles were formed on the rubbing surface of Si3N4 due to the friction-induced chemical reaction of Si3N4 with H2O, which were further aggregated into the silica gel with the assistance of ions in seawater. Because of the boundary lubrication of the silica gel layer, both the lowest friction coefficient and the smallest wear rates of Si3N4 and 316 steel were obtained in seawater. ► Excellent lubrication was obtained for Si3N4/316SS in seawater. ► The wear rates of the both Si3N4 and 316SS were the lowest in seawater. ► The tribochemical reaction of Si3N4 and H2O forms the colloidal silica in water. ► The colloidal silica can be aggregated into silica gel in seawater. ► The excellent lubrication in seawater is attributed to the deposited silica gel.