Chunfu Hong

Microstructure and tribological properties of Ti-contained amorphous carbon film deposited by DC magnetron sputtering

Pure amorphous carbon (a-C) film and that with a small amount of Ti were deposited on high speed steel (W18Cr4V) substrates by means of dc closed field unbalanced magnetron sputtering. The chemical composition and microstructure of the a-C films were performed using x-ray photoelectron spectroscopy, x-ray diffraction, Raman spectra, and transmission electron microscopy. The mechanical and tribological properties were evaluated using a nanoindentor, Rockwell and scratch tests, and a conventional ball-on-disk tribometer, respectively. The pure a-C film showed the high hardness (53 GPa), elastic modulus (289 GPa), but the poor adhesive strength. When adding a small amount of Ti to the a-C film, both the adhesive strength and the tribological properties were improved. The Ti contained a-C film had the low wear rate (1.9×10−17 m3 N−1 m−1) and friction coefficient in humid air.

Structure of sp2 dominant a-C film with superhardness

The mechanical properties of amorphous carbon (a-C) films strongly depend on the film structure. This paper reports on the superhardness of an a-C film resulting from a sp2 dominant microstructure synthesized by magnetron sputtering. The inherent medium compressive stress ensures the film is deposited with a thickness of 1.5 µm. The microstructure of the film with sp2 sites embedded in the amorphous matrix is responsible for the high elastic recovery and superhardness behaviour.

Preparation and Tribological Properties of Amorphous Ti/C Multilayers by Pulsed Laser Deposition

Amorphous Ti/C multilayers were prepared on titanium-alloy and silicon (100)-wafer substrates by pulsed laser deposition. Films with different Ti concentration were synthesized by changing the ablating time for Ti and C targets. The morphology and microstructure of Ti/C multilayers were characterized by scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD). Both of the Ti and C monolayers were amorphous. The metallic Ti stimulated the formation of more amorphous carbon phase by reducing the sp2 aromatic bonds and elongating the C-C chain bonds. The tribological properties of Ti/C multilayers were investigated by ball-on-disk tribometer. The pure C film and the multilayers containing more than 68.8 at.% of Ti showed low wear resistance. The multilayer contained 36.8 at.% of Ti exhibited the lowest wear rate at 3.54×10–16 m3/N·m. The formation of carbon related interlayer and its effect on tribological performance of the films were discussed.