Tribological behaviour of plasma-sprayed Al2O3 coatings under severe wear conditions

Plasma-sprayed alumina coatings are widely used as wear resistant coatings on a variety of metallic substrates. However, the particular structures of plasma-sprayed coatings (lamellar microcracks, unmolten particles, weak interfaces and high porosity) affect their mechanical properties and consequently their tribological behaviour. The present work deals with the wear behaviour of a 450 μm thick Al2O3 coating deposited on spheroidal graphite (S.G.) cast-iron substrate by Atmospheric Plasma Spraying (APS). Wear tests were carried out under severe conditions (normal force varying from 50 to 160 N, sliding speed: 1.40 m/s and average relative humidity (RH): 60%), using as a counterbody a quenched D2 tool steel. The microstructural characteristics of the ceramic coating were correlated to the evolution of both the friction and the wear coefficients and to the wear mechanisms involved.