Influence of carbon content on the microstructure and tribological properties of TiN(C) coatings in water lubrication

TiN(C) coatings with different carbon content were deposited on Si(100) wafers and 316L stainless steel disks using unbalance magnetron sputtering (UMS) from Ti and C targets in a mixture of N2 and Ar gases. The microstructure and phase of TiN(C) coatings were observed and analyzed using field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD), and the bonding structures of TiN(C) coatings were analyzed using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS). The friction and wear properties of TiN(C) coatings sliding against SiC balls in water were investigated using ball-on-disk tribometer, and the wear tracks of the TiN(C) coatings were observed using 3D-profilometer and FE-SEM. The results showed that the orientation of TiN (111) changed to TiN(100) with an increase in the C target current while the peak of TiC(400) was observed at the C target current beyond 2 A. When the C target current varied in the range of 1–3 A, the TiC, Ti(C,N),CN bonds were observed, whereas the DLC-rich area with CC bonds was detected as the C target current higher than 2 A. The hardness of TiN(C) coatings first increased to 32 GPa at the C target current of 1 A, and then decreased gradually with further increment in the C target current. The lowest friction coefficient of 0.24 and the lowest specific wear rate of 3.3 × 10− 6 mm3/Nm were obtained simultaneously as the TiN(C) coatings were deposited at the C target current of 3 A.