The effect of sputtering power on the structural and tribological behaviors at elevated temperature of Ta/Si co-doped DLC films

Ta and Si with various concentrations was co-doped into DLC films by plasma enhanced magnetron sputtering technique to improve its thermal stability and frictional performance at elevated temperature from 25 °C to 300 °C. Results showed that the doped Si and Ta mainly formed carbide in the film but play different role in the structure of the film. The sp3C content, surface roughness, hardness and adhesion strength increased firstly and then decreased with increasing content of doped elements in the film. The thermal stability and frictional performances at higher temperature was improved by higher content of doped element. It is notable that the film (with Si content of 4.47 at.% and Ta content of 2.44 at.%) exhibited low wear rates from 10−7 to 1 × 10−6 mm3/Nm at different temperatures owing to its higher sp3C content (18.2 %), proper nano-carbide, and thus higher hardness (11.09 GPa) and lower internal stress (0.24 GPa). The excellent frictional performances of this film tested at 300 °C was due to the reduced graphitization of the film, accompanied with the SiC nanoparticles and Ta5Si3 phase formed during the friction.