Tribological and micromechanical performance of hard yet tough TiSiN/WN coatings: An experimental analysis of multilayer effects

Hard nitride coatings have the potential to serve as protective layers for cutting tools due to their excellent mechanical properties and wear resistance. To improve their mechanical, tribological, and high-temperature oxidation characteristics, the structural design of the coating is crucial. This study explores the micromechanical and tribological properties of multilayer WN/TiSiN and monolayer WN and TiSiN coatings prepared using magnetron sputtering. We compare the adhesion strength, wear resistance, and failure mechanisms in these systems. The multilayer WN/TiSiN coating demonstrates superior adhesion strength and crack resistance. Scratch tests confirm cohesive-adhesive failure modes with spallation localized to interfacial zones, allowing the coating to withstand extra loading. Tribological analysis revealed distinct wear mechanisms among the coatings. While the WN coating had the lowest wear rate (1.3 × 10⁻⁶ mm³/Nm), its poor adhesion and susceptibility to failure under stress reduced its reliability. Conversely, the TiSiN coating exhibits higher wear rates (2.4 × 10⁻⁶ mm³/Nm) but maintains stable performance through oxide film formation. On the other hand, the WN/TiSiN multilayer coating combined the strengths of both monolithic layers with moderate wear rates (1.7 × 10⁻⁶ mm³/Nm) and a low coefficient of friction (0.5). Raman spectroscopy confirmed the formation of protective oxide films, such as WO₃ and TiO₂, contributing to reduced wear and enhanced stability.