Tribological Behavior of a Si3N4/Carbon Short Fiber Composite under Water Lubrication

The tribological behavior of monolithic Si₃N₄ and a Si₃N₄/carbon fiber composite has been assessed under high load and low speeds in an aqueous environment. The results showed that the friction coefficient of the Si₃N₄ was not significantly reduced when compared with dry sliding, and this was attributed to the failure to maintain a lubricating layer between the solid–solid surfaces. In the case of the composite, the initial high friction coefficient was reduced shortly after the beginning of the wear test and maintained a low value (about 0.03) throughout. This was attributed to the solid lubricating effect of the composite resulting in lower stress at the contact asperities, preventing the removal of the lubricating layer.