Tribochemical effects on CNx films

CNx thin coatings have been deposited by de magnetron sputtering using a gr aphite target in nitrogen atmosphere under different experimental condition s. X-Ray photoelectron spectroscopy, electron-energy loss spectroscopy, nuc lear magnetic resonance and Fourier-transformed infrared spectroscopy were used to elucidate the structural chemistry of each film. The tribological b ehavior has been investigated using a reciprocating pin-on-flat tribometer in a wide range of environmental conditions: ambient air, dry air and nitro gen. Tribochemical effects in relation to the nature of the surrounding atm osphere during friction tests are presented. Strong relationships between t he N/C ratio, the nature of C-N bonds and the friction behavior are highlig hted and discussed. An optimum in the friction and wear properties was foun d for a maximum in the C=N/C=C ratio for the studied set of CNx samples. Th e XPS/AES analysis of the sliding counterfaces support a destabilization of the CNx network under friction and build-up of a carbon rich tribolayer un der steady-state. (C) 2000 Elsevier Science B.V. All rights reserved.