Plasma source ion implantation of nitrogen, carbon and oxygen into Ti-6Al-4V alloy

Abstract

Plasma source ion implantation (PSII) has been under extensive research as an innovative technique for ion implantation of three-dimensional objects. A PSII device has been built and used to study nitrogen, carbon and oxygen ion implantation into Ti-6Al-4V orthopaedic alloy. The r.f. plasma generated using an antenna located inside the vacuum chamber was measured to have densities of 10(9)-10(10) cm(-3) at 0.5 m Torr for neutral pressure. The target bias voltage and current during implantation were monitored with a voltage divider and a current transformer. The bias voltage was found to have a rise time of about 5 mu s and flatness over the pulse width of 20 mu s. The Auger analysis of the implanted samples was shown to have depth distributions typical for ion implantation and the implanted layers were found to have undergone chemical state changes. The implantation time dependences were different for nitrogen, carbon and oxygen ion implantation. The implanted samples showed higher hardnesses especially at low loads in the order of oxygen, nitrogen and carbon ion implantation.