Enhanced environmental adaptability of sandwich-like MoS2/Ag/WC nanomultilayer films via Ag nanoparticle diffusion-dominated defect repair†

Abstract

Robustness and environmental adaptability are crucial for molybdenum disulfide (MoS₂) films to minimize friction and wear in industrial applications. However, current sputtered MoS₂ films suffer from inherent defects, including insufficient hardness, poor crystallinity, and susceptibility to oxidation, thereby limiting their longevity and reliability. Here, we present a sandwich-like nanomultilayer architecture comprising alternating MoS₂ and tungsten carbide (WC) layers integrated with Ag nanoparticles. This architecture demonstrates robust corrosion resistance, effectively protecting the MoS₂ within the film for over 18 months of air exposure and exhibiting minimal corrosion during 21 days of salt spray tests. The remarkable environmental stability of the sandwich-like MoS₂/Ag/WC nanomultilayer film is attributed to the creation of numerous heterogeneous interfaces and the spontaneous diffusion and repair of Ag atoms through defect channels of the film, impeding the penetration of corrosive agents. Furthermore, during the frictional process, Ag, characterized by its inherent high mobility and ductility, facilitates the formation of a dense tribofilm on its counterpart ball, encapsulating formed metal oxides to prevent adhesive wear. As a result, the film exhibits a significantly reduced wear rate (1.25 × 10⁻⁷ mm³ N⁻¹ m⁻¹) even after long-term salt spray corrosion and air exposure. This study offers a general route for designing MoS₂-based materials toward long-lifetime and environmental adaptability via self-repair mechanisms.