Friction and wear properties of plasma-sprayed Cr2O3-BaCrO4 coating at elevated temperatures

Chromium oxide is widely used as a tribological coating material in high-temperature applications requiring high wear resistance and lubricity. Herein, an attempt has been made to further improve the friction and wear properties of Chromium oxide coatings by incorporating BaCrO4 as a high temperature solid lubricant. The Cr2O3-10 wt% BaCrO4 high temperature self-lubricating ceramic was prepared by atmospheric plasma spraying (APS). The friction and wear characteristics of the Cr2O3-BaCrO4 composite coating coupled with Si3N4 balls from 25 degrees C to 700 degrees C were measured by a high temperature tribological tester and compared with that of pure Cr2O3 coating. Results showed that the Cr2O3-BaCrO4 coating possessed compact and lamellar structure with features of chromates fully spreading in it. Cr2O3-BaCrO4 coating did not exhibit improved tribological performance until the temperature was elevated to 400 degrees C and above. Surface brittle fracture could be mainly responsible for the poor tribological properties of Cr2O3-BaCrO4 coating at 25 degrees C and 300 degrees C. The adaptive formation of BaCrO4 at 400 degrees C and above on the worn surfaces of Cr2O3-BaCrO4 coating played a vital role in improving the frictional force on ceramic surfaces and the wear resistance of the coatings and counterpart balls despite the significant decomposition of BaCrO4 during spraying.