The tribological properties of TZP-graphite self-lubricating ceramics

A nano processing technique was used to produce TZP-graphite self-lubricating ceramics. The nano size ZrO2 powder was prepared by a co-precipitation method. The TZP-graphite composites were produced by a hot-pressing (HP) fast-sintering technique. Wear and friction properties of these composites were determined on a ball-on-disc tribotester in air and water and it was found that the graphite additive is effective in reducing the coefficient of friction of TZP ceramics, especially in water. Under dry sliding the critical graphite content is 13.3 vol.%. When the graphite content is higher than this value, the coefficient of friction of a GCr15 steel/TZP-graphite sliding couple decreases from 0.56 to 0.29, but the wear rate of TZP-graphite increases rapidly. In water, the coefficient of friction of the GCr15 steel/TZP-graphite (2.9 vol.%) sliding couple can approach 0.04, and the low friction duration time decreases with the increase of normal load. Additionally, in water, TZP-graphite composites have better wear resistance than TZP ceramics.