COMPOSITION, STRUCTURE AND TRIBOLOGICAL PROPERTIES OF AMORPHOUS-CARBON NITRIDE COATINGS

Carbon nitride thin films were synthesized using d.c. unbalanced magne tron sputtering of a high-purity graphite target in a nitrogen-contain ing plasma onto various substrates held at ambient temperatures. The N /C ratio was found to vary from zero to 0.8 depending on deposition co nditions. There was evidence of multiple bonding states for carbon and nitrogen (sp, sp(2) and sp(3)), and the bulk of the film was found to be amorphous. Nanoindentation studies showed that under appropriate s ubstrate bias conditions the carbon nitride coating hardness can be en hanced to levels well above that of conventional amorphous hard carbon coatings. CNx coatings replicate the substrate topography, giving ris e to surface roughness equal to or better than the original substrates . Lubricated tribotesting showed the relationship between wear perform ance and deposition conditions. Under pure sliding in air, the CNx coa ting provided a 30-fold reduction in wear rate for M2 steels (compared with uncoated M2) under our testing conditions.