Formation of titanium nitride barrier layer in nickel-titanium shape memory alloys by nitrogen plasma immersion ion implantation for better corrosion resistance

Ray W.Y. Poon, Joan P.Y. Ho, Xuanyong Liu, C. Y. Chung, Paul K. Chu, Kelvin W.K. Yeung, William W. Lu, Kenneth M.C. Cheung

    Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

    61 Citations (Scopus)

    Abstract

    Nickel-titanium shape memory alloys (NiTi) are potentially useful in orthopedic implants due to their super-elasticity and shape memory properties. However, the materials are vulnerable to surface corrosion and the most serious issue is out-diffusion of toxic Ni ions from the substrate into body tissues and fluids. In this paper, we describe our fabrication of TiN barrier layers in NiTi by nitrogen plasma immersion ion implantation followed with vacuum annealing at 450°C or 600°C. Our results show that the barrier layer is not only mechanically stronger than the NiTi substrate, but also is effective in impeding the out-diffusion of Ni from the substrate. Among the samples, the 450°C-annealed TiN barrier layer possesses the highest mechanical strength and best Ni out-diffusion impeding ability. The enhancement can be attributed to the consolidation of the Ti-N layer resulting from optimal diffusion at 450°C. © 2005 Elsevier B.V. All rights reserved.
    Original languageEnglish
    Pages (from-to)20-25
    JournalThin Solid Films
    Volume488
    Issue number1-2
    DOIs
    Publication statusPublished - 22 Sept 2005

    Research Keywords

    • Corrosion resistance
    • Hardness
    • Nickel-titanium shape memory alloy
    • Plasma immersion ion implantation
    • Titanium nitride

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