Tribological behavior of YSZ based composite coatings containing Ag, Sb₂O₃ and Ag/Sb₂O₃ from 25 to 800 °C

YSZ based composite coatings, containing Ag or Sb₂O₃ or Ag/Sb₂O₃, are fabricated using atmospheric plasma spraying technology. The phase composition, microstructure and mechanical properties are characterized. The influence of Ag, Sb₂O₃ and Ag/Sb₂O₃ on the tribological behavior of the YSZ based composite coatings sliding against Al₂O₃ ball was investigated from 25 to 800 °C. The results show that the introduced Ag in YSZ/Ag coating provides effective lubrication below 500 °C, while the presence of Sb₂O₃ deteriorates the wear behavior due to its volatilization and the deteriorative mechanical strength of YSZ/Sb₂O₃ coating. The YSZ/Ag/Sb₂O₃ coating with dual addition of Ag and Sb₂O₃ exhibits excellent friction and wear behavior in a broad temperature range. Such an improvement in tribological performance is attributed to the abundant supply of Ag covering on the worn surface. It is demonstrated that the diffusion channel of Ag increases due to the volatilization of Sb₂O₃ at high temperatures and the high porosity of the YSZ/Ag/Sb₂O₃ coating, which continuously provides lubricant Ag for the contact interface. The tribo-induced layer, composed of Ag, residual Sb₂O₃ and ZrO₂ wear debris, play a significant role in providing effective lubrication at elevated temperature.