Effects of annealing treatment on tribological behaviour of tungsten-doped diamond-like carbon film under lubrication (Part 1): Chemical composition, mechanical properties and tribological behaviour under base oil

Tungsten-doped diamond-like carbon (W-DLC) films were prepared by magnetron sputtering, followed by annealing in the temperature range of 100-500 degrees C. The effects of the annealing treatment on the chemical compositions, mechanical properties and tribological behaviours of annealed W-DLC films with a base oil were tested by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, x-ray diffraction and nanoindenter tests. The results indicated that increasing the annealing temperature led to a decrease in the thicknesses and hardness values of the W-DLC films due to the graphitization and oxidation of the film surfaces. However, the structures of the W-DLC films annealed at 500 degrees C were destroyed. Under poly-alpha olefin lubrication, when the annealing temperature was lower than 300 degrees C, the tribological properties of the W-DLC films were stable. This occurred because the graphitization of the sample surface was conducive to the removal of abrasive particles.