Tribological behavior of various ceramic materials sliding against CF/PTFE/graphite-filled PEEK under seawater lubrication

Abstract

In order to select appropriate antifriction and wear resistance material combinations for key frictional pairs in seawater hydraulic components, tribological characteristics of SiC, Si3N4, Al2O3, and ZrO2 ceramics sliding against carbon fiber/polytetrafluoroethylene/graphite-filled polyetheretherketone composite lubricated with seawater were comparatively investigated with a ring-on-ring test rig. The results show that the nonoxide ceramics (Si3N4 and SiC), especially the Si3N4 ceramic, exhibited lower friction coefficients and smaller wear rates than those of oxide ceramics (Al2O3 and ZrO2). And the tribological behaviors of polyetheretherketone/Si3N4 tribopair under dry friction, pure water, and seawater lubrications are further comparatively studied to explore the effect of lubricating medium on the tribological characteristics of Si3N4 ceramic. It is found that the lubricating effect of SiO2 and Si(OH)4 films generated by tribo-chemical reaction between Si3N4 and water is the main factor for the relatively low friction coefficient and wear rate of polyetheretherketone/Si3N4 tribopair under aqueous lubrication. Under seawater lubrication, the Mg(OH)2 and CaCO3 deposition layers caused by the chemical reaction of Mg2+ and Ca2+ in seawater could inhibit the generation of SiO2 and Si(OH)4 films and increase the counterface roughness. As a result, the tribological behaviors of polyetheretherketone/Si3N4 tribopair are worse under seawater lubrication than that of pure water lubrication.