Microstructure, Mechanical, and Tribological Properties of Mo2N/Ag-SiNx Nanomultilayers with Varying Modulation Periods

The multilayered Mo2N/Ag-SiNx self-lubricant films were designed and deposited using a DC (Direct Current) magnetron sputtering system under mixed gas atmosphere of N2 and Ar. The modulation ratio (thickness ratio of Mo2N to Ag-SiNx) was fixed at 2:1, while the modulation periods (thickness of Mo2N and its adjacent Ag-SiNx layer) were set at 20, 40, and 60 nm. The results indicated that all multilayer films, regardless of modulation period, exhibited a combination of face-centered cubic (fcc) and amorphous phases. Specifically, fcc-Mo2N was detected in the Mo2N layers, while fcc-Ag and amorphous SiNx co-existed in the Ag-SiNx layers. The multilayered architecture induced residual stress and interface strengthening, resulting in hardness values exceeding 21 GPa for all films. Compared to Mo2N and Ag-SiNx monolayer films, the multilayer structure significantly enhanced tribological properties at room temperature, particularly in terms of wear resistance. The Mo2N/Ag-SiNx multilayer films exhibit ~25% lower friction than Ag-SiNx, ~3% lower than Mo2N, and achieve remarkable wear rate reductions of ~71% and ~85% compared to Ag-SiNx and Mo2N, respectively, demonstrating superior tribological performance. The synergistic effects of both modulation layers and relative high hardness were key factors contributing to the enhanced tribological behavior.