Ceramics-Silikáty 55 (4) 305-311 (2011)

TRIBOLOGICAL PROPERTIES OF TiB_x AND WC/C COATINGS

F. Lofaj, M. Mikula, B. Grančič, G. Cempura, P. Horňák, P. Kúš, D. Kottfer

Tribological properties of TiB_x and WC/C coatings have been studied using the ball-on-disc method at room and elevated temperatures in air to investigate their behavior under conditions approaching high performance dry cutting. The average room temperature coefficients of friction (COF) of both nanocomposite DC magnetron sputtered TiB_x coatings and PECVD WC/C coatings were in the range 0.2-0.6. The lowest value of TiB_x coatings of 0.16 was achieved in case of prefferentially oriented stuctures deposited at the highest negative bias. The lowest COF of WC/C was around 0.11. The increase of testing temperature to 450°C caused the increase of COF up to approximately 0.7-0.8. The experiments at elevated temperatures suggest the existence of the oxide transfer film with higher COF than that of the sliding contact without the film. Although both coating systems have relatively high COF values at elevated temperatures, they exhibit elements of some adaptive behavior.

Keywords: Coefficient of friction, Thin nanocomposite coatings, TiB₂, WC/C, Transfer film