Hydrogen-free Cu: Amorphous-C: N Coating on TC4 Titanium Alloy: The Role of Gas Ratio on Mechanical and Antibacterial Potency

Ti-6Al-4V alloy, also called TC4, substrates are sputter-deposited by Cu: amorphous-C: N (Cu:a-C:N) thin coatings using planar magnetron sputtering physical vapor deposition device. Mixtures of argon and nitrogen at different ratios are selected as the sputtering atmosphere, and no hydrocarbon gas is used. Correlation of microstructure, morphology, surface properties, antibacterial characteristics, and mechanical performance of the coatings to the N2/Ar ratio are discussed. The outcomes from Raman spectroscopy confirm the construction of the DLC (Diamond Like Carbon) phase in the microstructure of the coatings. The thin coatings synthesized at higher N2/Ar ratios show more increased amount of sp^3 hybridization, improved wettability, higher internal stress, and enhanced mechanical properties, i.e., higher hardness. However, these are accompanied by lower antibacterial performance. Plastic hardness (H) value of the thin coatings increased from about 2 GPa to 13 GPa by increasing N2/Ar ratio. However, bacterial reduction percent of the thin coatings decreased from 100 to 65% as N2/Ar ratio increased. The resultant outcomes reveal the critical role of the N2/Ar ratio on tailoring the antibacterial properties of Cu: a-C: N thin coatings as well as mechanical ones.