Tribological behavior of tetrahedral amorphous carbon (ta-C) coatings at elevated temperatures

• The tribological behavior of ta-C coatings varies with temperature.
• ta-C shows lower friction at 200–400 °C than at 23 or 100 °C.
• Carbon transfer layers are formed on Si3N4 balls at 200–400 °C.
• ta-C is subject to severe delamination at 500 °C.

In this study, tribological behavior of tetrahedral amorphous carbon (ta-C) coatings was investigated at elevated temperatures, from which it was found that it could be broadly defined by three distinct temperature regions: Region I at 23 and 100 °C; Region II at 200, 300, and 400 °C; and Region III at 500 °C. A qualitative analysis of the toughness and adhesion of the ta-C coatings within each of these regions was conducted by scratch testing. The formation of a transfer layer on Si3N4 balls in Region II was determined as the cause of a reduced friction and higher wear rate when compared with Region I. In Region III, the generation and propagation of cracks in the ta-C coating resulted in severe delamination.