Tribological behavior of plasma sprayed carbon nanotubes reinforced TiO2 coatings

Intrinsic structural limitations of plasma-spray TiO2 coating deteriorate its wear resistance. Herein, CNTs are incorporated in the coating to assess their effects on the microstructure and tribological properties. Structurally, degradation degree of CNTs in TiO2 matrix during plasma spraying was revealed by Raman spectroscopy. And high resolution transmission electron microscopy manifested that TiO2/CNT interface was well bonded along with presence of notable interfacial carbothermic product TinO2n-1 at atomic scale. The phenomenon indicates a beneficial effect for transferring stress from matrix to CNTs effectively. Then, the influence of CNTs on coating's friction behavior was investigated by zirconia ball-on-disk tribometer under dry-sliding condition. As compared to TiO2 coating, the nanocomposite coating exhibited a moderate decrease in friction coefficient and an enormous reduction (∼93.6%) in wear volume. The remarkable advance in tribological properties of the reinforced coating can be attributed to four kinds of frictional effects of CNTs: tribo-reorientation, tribo-protruding, tribo-film and tribo-degradation.