Effects of Deposition Temperature on Microstructure and Tribological Properties of Pulsed Laser Deposited WS_x Films

WS_x solid lubrication films were deposited on monocrystalline silicon substrates at various temperatures by pulsed laser deposition. The composition, morphology and microstructure of the films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometer respectively. The tribological behavior of the films were investigated using a ball-on-disk tribometer in atmosphere (relative humidity 50% to 60%). The results show that the film deposited under room temperature was of crystallite structure. As rising the substrate temperature from room temperature to 300 ℃, the surface of the film became smoother and more compact, and the bonding strength between film and substrate and the crystallinity degree of WS_x phase increased. However, the atom fraction ratio of sulfur to tungsten of the film (S/W ratio) decreased from 1.84 to 1.49. The friction coefficient was inversely correlated with the S/W ratio in the substrate temperature range of RT~200 ℃. A great amount of crystalline WS₂ was formed within the film at a substrate temperature of 300 ℃, and the film exhibited the lowest friction coefficient and excellent wear resistance.