Molybdenum disulfide (MoS2) has been extensively utilized as a solid lubricant in various high-performance industries, including aerospace, nuclear energy, mechanical engineering, and electronics, owing to its exceptional lubricating properties that arise from its unique layered structure that facilitates easy shear between basal planes. However, a major challenge for MoS2 thin films is their inherent sensitivity to environmental conditions, particularly exposure to atmospheric moisture, salt fog, and high temperatures, which can cause oxidation. This oxidation compromises tribological performance and significantly reduces the service life of the films, and thereby, limiting their applicability in harsh environments. To address these limitations, the development of MoS2-based films with enhanced environmental stability is a key research topic. In this study, we successfully synthesized MoS2/ WB2 nanocomposite and MoS2 / WB2 superlattice films using unbalanced magnetron sputtering, a versatile and effective thin-film deposition technique. The primary objective was to enhance the environmental adaptability and mechanical properties of MoS2 films while maintaining their low-friction characteristics. The experimental findings revealed that the introduction of WB2 not only promoted the preferential growth of MoS2 along the (002) crystal plane, but also resulted in the formation of films with smooth surfaces and dense microstructures. These structural enhancements are crucial for improving the environmental stability and tribological performance of the MoS2 films. Notably, the MoS2/ WB2 superlattice film exhibited superior mechanical properties when compared with its nanocomposite counterpart, with a hardness of approximately 7.9 GPa and a high H / E ratio of 0.097. These properties are primarily attributed to the abundant MoS2 (002) planes aligned parallel to the substrate and nano-multilayer interfaces within the superlattice structure, which collectively contribute to the enhanced resistance of the film to environmental degradation. One of the most significant findings of this study is the remarkable corrosion resistance of the MoS2 / WB2 superlattice film in a neutral salt spray environment. The film maintained a low friction coefficient and wear rate before and after exposure to corrosive conditions. Specifically, the friction coefficient in an atmospheric environment was approximately 0.06, with a wear rate of 1.94 x 10(-7)mm(3) / (N.m). After five days of salt spray corrosion, the friction coefficient increased slightly to 0.10, with a wear rate of 7.15 x 10(-7)mm(3) / (N.m). Even after ten days of salt spray exposure, the film exhibited friction coefficients of 0.13 and a wear rate of 9.01 x 10(-7)mm(3) / (N.m), indicating minimal degradation and exceptional durability. Conversely, the composite film structure showed a significant deterioration in friction performance after a similar salt spray exposure, underscoring the superior environmental stability of the superlattice design. The mechanisms underlying the enhanced performance of the MoS2 / WB2 superlattice film are closely linked to its high H / E ratio and excellent corrosion resistance, which facilitate the formation of a continuous and dense tribofilm on the surface during sliding. This tribofilm, primarily composed of MoS2 nanosheets and metal oxide (MeOx) particles, acts as a protective layer, reducing direct contact at the sliding interface, and thereby, minimizing friction and wear. The persistence of low friction coefficients and wear rates even after prolonged exposure to corrosive environments highlights the potential of MoS2 / WB2 superlattice films for applications under harsh conditions, where high mechanical performance and environmental stability are required. MoS2 / WB2 superlattice films developed in this study represent a significant advancement in the field of solid lubricants. The combination of high hardness, excellent corrosion resistance, and sustained low-friction performance under corrosive conditions makes these films highly suitable for use in demanding environments, such as aerospace and nuclear energy sectors. The novel approach of integrating WB2 into a superlattice structure with MoS2 not only addresses the environmental sensitivity of traditional MoS2 films, but also opens new avenues for the design of high-performance solid lubricants with enhanced durability and reliability. This study provides a robust foundation for future research aimed at optimizing the composition and structure of MoS2-based nanocomposite films to improve their tribological properties and environmental resistance.
