Effect of Spraying Power on the Tribological Properties of Alumina and Alumina-Graphite Coatings

Abstract

Atmospheric plasma spraying is used to deposit alumina and alumina-graphite composite coatings. The influence of arc current (plasma temperature) on the microstructure, roughness, elemental composition, and phase composition of the coatings is analyzed by scanning electron microscopy (SEM), surface roughness testing, energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The tribological properties of the sprayed coatings are analyzed using a tribometer with a ball-on-flat configuration. The roughness of the as-sprayed coatings increases and the size of the granules decreases with the increase in plasma temperature. The results demonstrate that the friction coefficients and wear rates are slightly reduced for Al2O3 coatings sprayed at higher arc currents. The Al2O3-graphite coatings register lower friction coefficient values than the Al2O3 coatings under dry sliding conditions.