Abstract
This study investigates the influence of multilayer architecture on the mechanical, corrosion, and tribological properties of Ti/TiN coatings deposited on biomedical Ti-6Al-4V alloy. Nine multilayer configurations were prepared by DC/RF magnetron sputtering using metallic Ti and ceramic TiN targets, with a fixed TiN/Ti ratio of 3:1 and varying total numbers of layers (3, 5, and 7) and deposition times (30, 60, and 120 min). A strict application of the 10% indentation depth rule was implemented to eliminate substrate effects, which revealed significantly higher intrinsic hardness values (540–740 HV) and indentation moduli (124–143 GPa) compared to the substrate (353 HV; 114 GPa). In contrast, conventional higher-load testing underestimated coating performance due to substrate dominance. Among the investigated architectures, the Ti/TiN-7 configuration exhibited the best balance of properties, combining high hardness (~690 HV), modulus (~137 GPa), improved corrosion resistance (Ecorr up to −0.13 V, Icorr reduced by an order of magnitude), and stable abrasive wear behavior. These findings demonstrate that both bilayer number and deposition time critically determine the mechanical and functional response of Ti/TiN multilayers. The results provide practical guidelines for the reliable characterization and design of multilayer coatings for biomedical and aerospace applications.