Self-Lubrication Mechanism of Plasma-Sprayed Cr2O3-Ag Nanocomposite Coatings at Room to Moderate Temperatures.

Lubrication mechanisms of plasma-sprayed Cr2O3-Ag nanocomposite coatings were studied by using ball-on-disk friction tests against tungsten carbide counterface at temperatures ranging from 25 to 500 °C. The Cr2O3-Ag nanocomposite coatings were fabricated from agglomerated granules of chromium oxide and silver nanoparticles by plasma spraying process under optimized parameters. The presence of semi-molten nanoparticle zones within the coating promoted a sliding wear behavior characterized by plastic deformation of nanostructured ceramic matrix coatings. The formation of a silver-rich tribofilm on top of the contact surface and tribodecomposition of Cr2O3, as well as tribo-oxidation of Ag at the sliding interface were found to be the controlling mechanisms of friction in these coatings at moderate to high temperatures. The lowest coefficient of friction (COF) at all temperatures was obtained for the Cr2O3-5 vol. % Ag coating due to the optimum condition of its silver-rich tribofilm. [ABSTRACT FROM AUTHOR]