Ceramics have important advantages in application due to their high hardness and stiffness, high temperature stability and wear resistance. However, often the coefficient of friction is too high in sliding contacts, resulting in high frictional losses. Therefore ceramic composites containing a soft, self lubricating phase have potential to be used in these applications as the presence of the soft phase as a second phase in the ceramic gives the possibility of gradual supply to the surface and additional control over the thickness of the soft surface layer.
In this research, a copper oxide doped zirconia composite (CuO-TZP) is used as a self-lubricating ceramic composite system. The frictional behaviour of this material has been experimentally studied at several temperature levels. Further, a model has been developed which includes the processes responsible for maintaining the soft third body layer at the interface. The developed model includes a source flow and wear flow in balance for a stable thin soft layer in the contact. The model can predict the thickness of the third body layer under several tribological conditions in the mild wear regime as well as the operational conditions at which a stable thin soft layer is formed.
It can be concluded from the research that the coefficient of friction of TZP can be significantly reduced by the presence of a thin Cu-rich layer on the surface. The tribological performance of CuO-TZP under dry sliding conditions strongly depends on the operational conditions, like velocity, contact pressure and temperature. The model shows that the supply of soft phase to the surface is mainly determined by soft phase concentration as well as the applied load while the removal is mostly influenced by the microgeometry of the counter surface.