Tribological Properties of Alumina-Zirconia Composite Coatings Prepared by Plasma Spraying

Abstract

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-ZrO 2 (t-ZrO 2 ) and with alumina, it was α-Al 2 O 3 and γ-Al 2 O 3 . 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 mm 3 /Nm for the composite coatings with certain exceptions.