Low Friction in CuO-Doped Yttria-Stabilized Tetragonal Zirconia Ceramics: A Complementary Macro- and Nanotribology Study

The tribological behavior of CuO-doped yttria-stabilized tetragonal zirconia (3Y-TZP) ceramics in the absence of additional lubricants was characterized by macroscale pin-on-disk measurements and nanoscale atomic force microscopy (AFM) for a broad range of velocities. The previously observed low shear strength interfacial layers generated in pin-on-disk tracks by Al2O3 ball counter surfaces on CuO-doped 3Y-TZP, as well as virgin surfaces, were probed quantitatively by AFM with Si3N4 tips as the counter surface. The observed trends in nanoscale coefficient of friction determined by AFM were found to be in agreement with data acquired using a pin-on-disk tribometer. The combined data support the notion that a layer of surface contaminations is removed during the initial sliding, and wear of high asperities occurs. Subsequently, an interfacial layer with low shear strength is generated during sliding. While these results do not provide an exhaustive explanation for the process of layer formation, they represent the first report of bridged nano- and macrotribological analysis of a compositionally heterogeneous low-friction, low-wear ceramic material and further confirm some of the key assumptions for the deterministic model reported previously by Pasaribu and Schipper.