Tribological Performance Of Plasma Sprayed Cr₂O₃-8TiO₂ Coatings

Plasma spraying is an important surface treatment technology. The coating can enhance and restore the surface of materials .At the same time material surface can get particular properties, so plasma spraying technology is widely used.Cr₂O₃-8TiO₂ coatings were prepared on a substrate of 45 steel by plasma spraying and hard chrome plating coatings were prepared. The micro-hardness and porosity of Cr₂O₃-8TiO₂ coatings and hard chrome plating coatings were tested. The microstructure and surface topography of ceramic coatings and hard chrome plating were observed by using optical microscopy (OM) and scan electron microscope (SEM). Energy dispersive spectroscopy (EDS) was used to measure the composition of the coatings. Cr₂O₃-8TiO₂ coatings and hard chrome plating coatings' frictional behaviour and wear mechanism in different friction conditions were studied.The Cr₂O₃-8TiO₂ coating has a typical laminar structure with about 10% porosity, while hard chrome plating coating has a dense structure with about 1% porosity. A relatively high micro-hardness with large variation between 1286～2143Hv was observed for Cr₂O₃-8TiO₂ coating, nearly twice as hard as hard chrome plating with micro-hardness of 860Hv.In dry-friction condition, friction coefficient and mass loss of Cr₂O₃-8TiO₂ coating were lower than that of hard chrome plating. And the higher sliding speed, friction coefficient of Cr₂O₃-8TiO₂ coating was lower. Due to high porosity, the wear mechanism of Cr₂O₃-8TiO₂ coating was micro-fracture wear. The hard chrome plating's wear mechanism was adhesive wear.In lubricated condition, friction coefficient of Cr₂O₃-8TiO₂ coating was lower than hard chrome plating's friction coefficient. In experiments which were carried out under 50N and 0．78m/s, ceramics coatings has an obviously better wear-resistance than the hard chrome plating. The mainly wear mechanisms of Cr₂O₃-8TiO₂ coating were abrasive wear and micro-fracture wear. And the main wear mechanisms of hard chrome plating were abrasive wear and adhesive wear.In conclusion, the plasma sprayed Cr₂O₃-8TiO₂ ceramic coating has a lower friction coefficient and mass loss than hard chrome plating.