Frictional characteristics of ceramics under water-lubricated conditions

Friction experiments were conducted on four kinds of ceramics (SiC, Si3N4. Al2O3 and ZrO2) against themselves in water under different contact pressures and sliding velocities. The variations of friction coefficients as a function of sliding distance, and the effects of mean contact pressure and sliding velocity on friction coefficients were shown. Friction coefficients lower than 0.03 were observed under a certain combination of mean contact pressure and sliding velocity for each material. The friction coefficient suddenly increased when the mean contact pressure was above a threshold value, which depended on both sliding velocity and the material of sliding pairs. SiC had a higher threshold value than the other three ceramics at every sliding velocity investigated.