Microstructures and tribological properties of MoS2/Mo2N multilayer gradient films deposited by reactive magnetron sputtering

Abstract

In order to compare the microstructures and tribological properties of films, pure Mo2N, pure MoS2, 3-layer and 13-layer MoS2/Mo2N gradient films were deposited by reactive magnetron sputtering. The crystalline structure, surface and cross-section morphologies, 3D surface topography, binding energy, hardness and tribological properties of films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atom force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), nanoindenter, and wear tester, respectively. The results indicate that the preferred orientation of MoS2 in gradient films has changed. The surface and cross-section structures of gradient films become denser with increasing the number of gradient layers. Average surface roughness (Ra) of pure MoS2 film is the highest, and Ra of 13-layer film is the lowest. The binding energy of MoS2 in the composite layer of gradient film has changed. The hardness of gradient film is higher than that of MoS2 and lower than that of Mo2N. The wear resistance of gradient films is much better than that of pure MoS2, and this phenomenon is more obvious under high load conditions. The improvement in the wear resistance of gradient films is attributed to the increase of dense, hardness, H/E and H3/E2. In the initial stage of friction, the 3-layer gradient film can maintain low friction coefficient (≤0.15), which is attributed to the thick MoS2 surface layer. The wear resistance of 13-layer is much better than that of 3-layer gradient film, because it has higher hardness, higher H/E and H3/E2 than 3-layer gradient film.

Keywords

• MoS2/Mo2N gradient films
• Magnetron sputtering
• X-ray diffraction
• Wear resistance
• Friction coefficient