Abstract The choice of metal dopant strongly influences the structural and tribomechanical performance of diamond-like carbon (DLC) coatings. In this study, two graded Ti-based architectures—Ti-TiC-TiZrC-a:C and Ti-TiC-TiZrC-TiZrCN-a:C—were deposited on AISI M2 tool steel by closed-field unbalanced magnetron sputtering with pulsed-dc biasing to clarify the effects of Zr and nitrogen incorporation. SEM observations revealed dense-graded morphologies with thicknesses of approximately 2 μm and 3 μm, respectively. XRD confirmed the formation of TiC and TiZrC phases in both coatings, with additional TiZrCN reflections in the nitrogen-containing system. Both coatings significantly increased hardness relative to the substrate, reaching 1280 ± 25 and 1300 ± 28 HK0.01, respectively; however, statistical analysis ( p ≈ 0.27) indicated no significant difference between them. Tribological testing showed that the Ti-TiC-TiZrC-a:C coating exhibited superior balance, with lower friction (0.090), a lower wear rate ((1.21 ± 0.03) × 10 −5 mm 3 /N·m), and a higher critical load (47 N). Nitrogen incorporation altered the phase constitution and stress state but did not enhance overall tribological performance. The results show that interlayer architecture and stress control are more decisive than compositional complexity in optimizing graded Ti-based DLC coatings.
Bülbül et al. (Mon,) studied this question.