TRIBOLOGICAL PROPERTIES OF ALUMINA-ZIRCONIA COMPOSITE COATINGS PREPARED BY PLASMA SPRAYING

The intent of this research was to determine the tribological trends of zirconia as an additive to a plasma-sprayed alumina coating matrix. For the deposition process, pure alumina and alumina-withzirconia (5%, 10%) weight percentages were employed to be coated on steel substrates using an airhydrogen plasma. The torch power was set to ~40 kW. The surface roughness for the alumina coatings were in the range from 2.6-3.2 μm and with additive percentages of zirconia, it was found to vary between 3.0-3.7 μm. XRD measurements indicated that the predominant phase in the alumina-zirconia coatings was tetragonal-ZrO2 (t-ZrO2) and with alumina, it was α-Al2O3 and γ-Al2O3. The tribological properties such as the friction coefficient and the wear-rate of the alumina-composite coatings had been inspected to evaluate its dependence on the type and concentration of the additive powders. An increase in friction-coefficient was observed with the addition of zirconia. The normalized wear rates were in the range of ~10-5 mm3/Nm for the composite coatings with certain exceptions.