Modulation of stress and mechanical properties in silicon- and titanium-doped tetrahedral amorphous carbon coatings via HiPIMS

This study implemented elemental doping modification of tetrahedral amorphous carbon (ta-C) coatings via high-power pulsed magnetron sputtering (HiPIMS) with reverse positive pulses. Systematic investigation revealed that both silicon and titanium doping effectively modulated the sp 3 /sp 2 bonding ratio in ta-C coatings. For silicon doping, an optimal concentration of 3% resulted in a significant increase in sp 3 -bond content to ∼85%, a high nanoindentation hardness of 49.3 GPa, a substantial reduction in residual stress to −3.4 GPa, and a low friction coefficient of 0.073. For titanium doping, an optimal concentration of 2% yielded an sp 3 -bond content of ∼83%, a hardness of 45.9 GPa, a residual stress of −4.2 GPa, and a friction coefficient of 0.083. However, comprehensive performance metrics were comparatively lower for titanium-doped coatings relative to their silicon-doped counterparts. The superior performance of silicon doping is attributed to the intrinsic characteristics of Si-C bonds, which more effectively relax network distortion while promoting sp 3 -hybridization and forming reinforcing SiC nanocrystallites. This work demonstrates that silicon doping not only preserves ultrahigh hardness but substantially alleviates residual stress while enhancing toughness, providing a critical theoretical and technological foundation for optimizing HiPIMS-fabricated high-performance ta-C coatings.