Study on the Performance of WS2 and WS2-C Composite Film

As an important solid lubricating material, tungsten disulfide has a wide range of applications in aerospace, machining, new energy vehicles, medical, electronics, digital and other fields due to its excellent tribological properties. However, the carrying capacity of pure WS2 film is low, and it is easy to absorb moisture and oxidize in humid air, which seriously shortens its service life.

Nowadays, in order to improve the carrying capacity and service life of pure WS2 film, scholars of Central South University use WS2, graphite and pure titanium as targets, and adopt twin target intermediate frequency magnetron sputtering, DC magnetron sputtering combined with ion enhancement methods. WS2 and WS2-C composite films were prepared on the surface of crystalline silicon wafer and TC4 alloy (Ti6Al4V) substrate.

Through scanning electron microscope (SEM), energy spectrometer (EDS), X-ray diffractometer (XRD), Raman spectrometer, metallographic microscope (OM), microhardness tester, scratch tester and ball-disk friction and wear tester, the microstructure, phase structure, mechanical properties and friction and wear properties of WS2 and WS2-C composite films were studied. The results show:

The WS2 film prepared by the intermediate frequency magnetron sputtering method has different degrees of S element loss. Its S/W atomic ratio is closely related to the working pressure and is not significantly affected by the deposition temperature. The WS2 film shows obvious that the surface of (002) crystal is preferentially grown. As the deposition temperature increases, the (002) diffraction peak of the film gradually weakens. The microhardness of the pure WS2 film is lower, and the film/base bonding strength is better. The WS2 film prepared at lower temperature has the lower the friction coefficient and good anti-friction effect, the higher the deposition temperature, the higher the friction coefficient of the film.

The WS2-C composite film prepared by co-sputtering the WS2 target and the graphite target has a compact structure, and the S/W atomic ratio is close to that of the WS2 film under the same conditions. With the increase of carbon content, the WS2((002) crystal plane of the composite film diffraction peaks gradually weaken. The appearance of tungsten carbide compounds increases the hardness of the film to a certain extent. The addition of carbon elements reduces the film/substrate bond strength of the composite film. As the carbon content increases, the friction coefficient of the composite film gradually increases, which means that its anti-friction effect is not as good as pure WS2 film, but its wear resistance life has been greatly improved. The friction coefficient of pure WS2 film and low carbon content composite film increases with the increase of load. As a result, for the composite film with higher carbon content, the friction coefficient is not significantly affected by the load, and the friction process of the film basically gradually stabilizes when the load becomes larger.

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