WS2/a‐C multilayer films exhibit good friction reduction but relatively low hardness and load‐bearing capacity. To further enhance the tribological properties of WS2/a‐C films, Mo layers with different thicknesses are introduced into WSx/a‐C multilayer films to fabricate WSx/Mo/a‐C/Mo multilayer films by magnetron sputtering. The microstructure and tribological properties of the films are characterized by X‐ray diffractometry, scanning electron microscopy, nanoindentation, and ball‐on‐disk tribotesting. The results show that the WSx/Mo/a‐C/Mo multilayer films have better mechanical and tribological properties than WSx/a‐C multilayer films. With increasing Mo single‐layer thickness, the hardness of the multilayer films initially increases and then decreases slightly; moreover, an increased elastic modulus and decreased adhesion are observed. The multilayer film with an Mo single‐layer thickness of 2 nm demonstrates the optimal set of comprehensive properties (i.e., a maximum hardness (H)/elastic modulus (E) ratio of 0.0793, H3/E2 ratio of 0.0812 GPa, binding force of 30.4 N, minimum friction coefficient of 0.187, and wear rate of 1.01 × 10−14 m3 N−1 m−1).
The manufacturing of multilayer films with improved mechanical and tribological properties has attracted attention recently for enabling their space applications. In this study, we aim to optimize the manufacturing process of WSx/a-C multilayer films by alternately depositing WS2, amorphous carbon (a-C), and Al metal on silicon substrates through magnetron sputtering. The microstructure and morphology of the multilayer films were investigated by x-ray diffractometry, scanning electron microscopy, and x-ray photoelectron spectroscopy. The mechanical and tribological properties of the films were evaluated in vacuum using a nanoindentation tester, ball-on-disk tribometer, and scratch tester. The results showed that the addition of an Al layer with an optimal thickness refined the microstructure of the films. The tribological properties of the films deteriorated with increasing thickness of the Al single layer. When the thickness of the Al film was 1 nm, the tribological properties of the films were optimal, and the adhesion was maximum (49.1 N). Hardness of the films gradually decreased with an increase in the thickness. Wear rate of the films decreased initially and then increased, and the wear rate was lowest when the thickness of the Al single layer was 2 nm (1.41 × 10−15 m3 N−1 m−1). By manufacturing films with optimal thickness, suitable tribological properties for vacuum applications can be achieved.
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