Tribological properties of a-CNx coatings sliding against SiC balls in ethylene glycol aqueous solution

Amorphous carbon nitride(a-CN_x) coatings were deposited on SiC disks by using ion beam assisted deposition, and their bonding structure and hardness were determined using X-ray photoelectron spectroscopy and nano-indenter, respectively. The contact angles on the surface of the a-CN _x coatings were measured with contact angle meter. The friction and wear behaviours of the a-CN_x/SiC tribopairs in ethylene glycol aqueous solution were investigated with ball-on-disk tribometer. The results indicated that the a-CN_x coatings contained 12at. % nitrogen and their bonding structure consisted of sp²C=N/C=C and sp³C-N bonds. The static contact angles on the a-CN_x coatings decreased with the ethylene glycol concentration. The lowest coeffi cient of friction of 0.019 was acquired as the ethylene glycol concentration was 10vol. %. When the ethylene glycol concentration increased, the specifi c wear rate of the SiC ball fl uctuated in the range of 5.9 × 10^-10∼1.1 × 10^-9 mm³ Nm^-1, while that of a-CN_x coatings varied in the range of 3.3 × 10^-8∼7.8 × 10^-8 mm³ Nm^-1.