Microstructure and water-lubricated friction and wear properties of CrN(C) coatings with different carbon contents

The CrN(C) coatings with different carbon contents were deposited using unbalanced magnetron sputtering via adjusting the carbon target current, and their microstructure and mechanical properties were characterized using Raman spectrum, X-ray photoelectron spectroscopy and nano-indenter, respectively. The water-lubricated tribological properties of the CrN(C) coatings against Si3N4 balls were investigated using the ball-on-disk tribometer. The results showed that the C content in the CrN(C) coatings increased gradually, and the peak intensity correlated to Cr7C3 crystal phase became stronger when the carbon target current increased. When the carbon target current was 1 A, the hardness of the CrN(C) coatings increased to 22.5 GPa due to formation of Cr7C3 phase and amorphous CNx, and a little amorphous carbon had positive effect on tribological properties of the CrN(C) coatings in water lubrication. On the other hand, CrN(C) coatings deposited at 2–4 A exhibited a lower hardness and deteriorated tribological properties, due to the presence of a major amount of Cr2O3 particles in the films.