Improvement on corrosion resistance of NiTi orthopedic materials by carbon plasma immersion ion implantation

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2006-01, Vol.242 (1-2), p.270-274
• Main Authors: Poon, Ray W.Y., Ho, Joan P.Y., Luk, Camille M.Y., Liu, Xuanyong, Chung, Jonathan C.Y., Chu, Paul K., Yeung, Kelvin W.K., Lu, William W., Cheung, Kenneth M.C.
• Format: Article
• Language: English
• Subjects: Corrosion resistance; NiTi shape memory alloys; Plasma immersion ion implantation and deposition; Surface morphology
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2005.08.045

Nickel–titanium shape memory alloys (NiTi) have potential applications as orthopedic implants because of their unique super-elastic properties and shape memory effects. However, the problem of out-diffusion of harmful Ni ions from the alloys during prolonged use inside a human body must be overcome before they can be widely used in orthopedic implants. In this work, we enhance the corrosion resistance of NiTi using carbon plasma immersion ion implantation and deposition (PIII&D). Our corrosion and simulated body fluid tests indicate that either an ion-mixed amorphous carbon coating fabricated by PIII&D or direct carbon PIII can drastically improve the corrosion resistance and block the out-diffusion of Ni from the materials. Results of atomic force microscopy (AFM) indicate that both C2H2-PIII&D and C2H2-PIII do not roughen the original flat surface to an extent that can lead to degradation in corrosion resistance.