A Study of the Wear Resistance of TiMoN/NbN Nano-Multilayer Coatings Deposited by Ca-PVD Technology Under Different Working Pressures

This study investigates the wear behaviour of TiMoN/NbN nano-multilayer coatings deposited by cathodic-arc PVD under two nitrogen working pressures (0.52 and 0.13 Pa). Although both coatings exhibit comparable total thicknesses (~10–11 μm) and a similar number of periods (~270), their structural integrity, interface coherence, and elemental distribution differ significantly with deposition pressure. The coating synthesized at 0.52 Pa develops a highly ordered, dense multilayer architecture, characterized by well-defined interfaces and a reduced microdefect density. Conversely, the coating deposited at 0.13 Pa displays pronounced interfacial waviness, disrupted periodicity, and increased defect concentration. Ball-on-disc tribological tests reveal a stable friction coefficient of 0.42–0.48 for the 0.52 Pa coating, whereas the 0.13 Pa coating shows an elevated and unstable friction response (0.60–0.70) with frequent fluctuations. Microstructural and chemical analyses of wear tracks indicate the formation of a robust, adaptive Ti–Nb–Mo–O tribofilm for the high-pressure coating, incorporating lubricious MoO3 and mechanically strengthening Nb2O5 phases. In contrast, the low-pressure coating produces only a thin, brittle TiO2-rich film lacking self-replenishing capability. These findings demonstrate that optimized nitrogen pressure is essential for achieving structurally coherent nanolaminates capable of forming functional tribofilms, thereby dramatically improving wear resistance in TiMoN/NbN nano-multilayer systems.