Tribological Properties of Cr₂O₃, Cr₂O₃-SiO₂-TiO₂ and Cr₂O₃-SiO₂-TiO₂-Graphite Coatings Deposited by Atmospheric Plasma Spraying

In this study, Cr2O3, Cr2O3-SiO2-TiO2 and Cr2O3-SiO2-TiO2-graphite coatings were formed by atmospheric plasma spraying. The influence of SiO2-TiO2 and SiO2-TiO2-graphite reinforcements on the surface morphology, elemental composition, structure and tribological properties of chromia coatings was determined. The friction coefficients and specific wear rates were investigated by a ball-on-flat configuration using 1 N and 3 N loads under dry-lubrication conditions. The addition of SiO2-TiO2-graphite resulted in the lowest surface roughness and the most homogenous surface of the coatings. The X-ray diffraction (XRD) measurements demonstrated that all as-sprayed coatings consisted of an eskolaite chromium oxide phase. The results showed that the Cr2O3-SiO2-TiO2 coating demonstrated the lowest friction coefficient values. The SiO2-TiO2 and SiO2-TiO2-graphite additives reduced the specific wear rates of Cr2O3 coatings by 30% and 45%, respectively. Additionally, the wear resistance was improved almost 45 times in comparison to the steel substrate.