Further improving the mechanical and tribological properties of low content Ti-doped DLC film by W incorporating

Highlights: • W and Ti atoms were introduced successfully into the film together by co-sputtering W/Ti twin-target. • Introduction of W atom significantly enhanced the hardness and retained the low internal stress. • The friction and wear resistance could be further improved significantly by W incorporating. - Abstract: W/Ti-doped diamond-like carbon (DLC) films were fabricated on Si substrates by co-sputtering W and Ti targets in methane and argon mixture atmosphere. The composition and the microstructure, internal stress, mechanical and tribological properties of the films were measured by X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), Raman spectra, BGS 6341 type film stress tester, nano-indentor and reciprocating ball-on-disc tester, respectively. The results indicated all films showed the amorphous structural characteristics and a constant thickness value of ∼600 nm (195 ± 15 nm Ti interlayer was designed in order to minimize the influence of Ti interlayer), and the Ti content increased from 0 to 34.5% as the W target current increased from 0 A to 14 A. As the W concentration increased from 0 to 2.6 at.%, the hardness increased to 12.7 GPa and the internal stress maintained at a low value and almost no change. Meanwhile, the friction coefficient and wear rate showed the lowest value (0.023 and 1.2 × 10⁻⁸ mm³/N m, respectively). With the W content increased to 34.5 at.% further, the internal stress, friction coefficient and wear rate of film are dramatically increased.