This work is devoted to investigation of mechanical and tribological properties of carbon nitride (CN$_{x}$) coatings deposited on the titanium IM125 and steel AISI321 substrates by the method of reactive magnetron sputtering of a graphite target at direct current in a mixture of gases argon/nitrogen. As shown, at pressure $p$ = 0.35 Pа, nitrogen concentration in a mixture of gases $C$ = 42-58%, substrate temperature $T_{substr}$ = 130°C, the highest values of hardness $H$ = 15/20 GPa, modulus of elasticity $E^{*}$ = 120-132 GPa, normalized hardness $H/E^{*}$ = 0.130-0.152, elastic deformation $\varepsilon_{es}$ = 4.03-4.6% are obtained, indicating increased ductility and wear resistance of the coating under friction. Wear-resistance testing conducted under dry friction by means of the ball-on-disc and ball-section methods show that high wear resistance is found in CN$_{x}$ coatings with the highest carbon ordering, and it is confirmed by high values of normalized hardness $H/E^{*}$ and $\varepsilon_{es}$. Testing in blood plasma of titanium IM125 samples with CN$_{x}$ coating in friction pair with chirulen yields low values of friction coefficient and wear intensity of chirulen equal to 0.079 and 0.65 mm/km, respectively.