SLIDING WEAR OF A PLASMA-SPRAYED AL2O3 COATING

Wear behaviours of plasma-sprayed Al2O3 coating in conformal contact sliding under dry and lubricated conditions against steel AISI D2 have been investigated under different loads at various speeds. A tangential impact wear model is proposed to explain the wear rise with speed and SEM analysis is carried out to identify the wear mechanisms. The results indicate that the wear behaviour of the Al2O3 coating in conformal contact differs from that in linear contact. The wear rate is lower in conformal contact in steady-wear state. Secondly, there exists a maximum-wear load both in dry sliding and lubricated sliding. Thirdly, there exists a minimum-wear sliding velocity of about 1 m s(-1) and a maximum-wear velocity of about 5 m s(-1) in dry sliding. The proposed tangential impact wear model could explain the wear rise of plasma-sprayed Al2O3 coating with the increased speed at the velocity range 1-3 m s(-1). Furthermore, in a lubricated situation, the wear of plasma-sprayed Al2O3 is small at low velocities below 1 m s(-1), and then increases sharply, proportional to the kinetic energy of the moving specimen, from 1 to 2.8 m s(-1). Finally, the failure types of plasma-sprayed Al2O3 coating when sliding against steel AISI D2 in conformal contact are: plastic deformation, adhesive wear and brittle fracture.