Corrosion and bio-tribological properties of Ti(CN)x hard coating on titanium alloy by the pulsed plasma electrolytic carbonitriding process

• Thickness and hardness of diffusion layer increase with decreasing pulse frequency.
• High frequency provides a denser diffusion layer showing high corrosion resistance.
• Wear rate decreases by an order of magnitude under 0.9% saline after the PEC/N process.
• Diffusion layer shows the lowest friction coefficient of 0.23 under calf serum.
• PEC/N treatment reduces wear rate by two orders of magnitude under calf serum.

Ti(CN)x hard coating was deposited on Ti6Al4V alloy by the pulse plasma electrolytic carbonitriding process in formamide electrolyte. The influence of pulse frequency on the corrosion and bio-tribological properties of PEC/N coating was investigated. The results showed that higher pulse frequency (15 kHz) provides a denser diffusion layer than low frequency markedly improving the corrosion resistance. The thickness and hardness of diffusion layers increase with decreasing pulse frequency and the wear resistance gets improved under dry friction. Carbonitriding layers greatly improve the bio-tribological behavior of Ti6Al4V alloy under saline and calf serum lubrication. The friction coefficient is reduced to 0.23 under calf serum lubrication and the wear rate decreases by two orders of magnitude compared with titanium alloy.