Effect of temperature on friction and wear behaviour of CuO-zirconia composites

Results of wear tests using an alumina ball sliding against 5 wt% copper oxide doped tetragonal zirconia polycrystalline (CuO-TZP) ceramics are reported as a function of temperature up to 700 degrees C. The specific wear rate and friction coefficient are strongly dependent on temperature. Below a critical temperature (T < 600 degrees C), CuO-TZP showed a high coefficient of friction as well as a high wear rate. This was ascribed to the formation of a rough surface, caused by brittle fracture and abrasive wear, based on observations by scanning electron microscopy (SEM), laser scanning microscopy (LSM) and X-ray photoelectron spectroscopy (XPS). However, above 600 degrees C a self-healing layer is formed at the interface and results in low friction and wear. The mechanism of layer formation and restoration is discussed and rationalized by onset of plastic deformation caused by a reduction reaction of CuO to Cu2O at high temperatures. (C) 2012 Elsevier Ltd. All rights reserved.