Tribological behavior of radio-frequency sputtering WS2 thin films with vacuum annealing

Thin films of tungsten disulfide (WS2) were deposited on 3Cr13 martensitic stain less steel substrate by radio-frequency (RF) sputtering. The as-deposited films were annealed at 473, 673 and 873K respectively for 2h in 510-4Pa vacuum. Composition of the films was inspected by energy dispersive spectroscopy. Surface morphology and structure properties were studied by scanning electron microscopy and X-ray diffraction techniques. Tribological behavior was also examined using tribometer. At 473K, the films exhibited low crystallization structure and no significant improvement in the tribological performance. At 673K, the tribological performance was improved and a transition from non-crystalline to hexagonal structure took in place. When the annealing temperature rose up to 873K, the films cracked and fell off from the substrate. The results suggested that with suitable technical parameters vacuum annealing could promote crystallization and improve tribological performance of RF sputtering WS2 films.