Effects of alloying elements on hard ceramic layer formation on surfaces of biomedical Ti-29Nb-13Ta-4.6Zr and Ti-6Al-4V ELI during gas nitriding

Masaaki Nakai, Mitsuo Niinomi, Toshikazu Akahori, Naofumi Ohtsu, Hideki Nishimura, Hiroyuki Toda, Hisao Fukui, Michiharu Ogawa

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Abstract

Formation of the reaction product layer on the surface of biomedical titanium alloys, Ti-29Nb-13Ta-4.6Zr (TNTZ) and Ti6A1-4V ELI (Ti64), during gas nitriding was investigated. These alloys were exposed to nitrogen atmosphere at 1023, 1073, 1123 and 1223 K. After the gas nitriding, a reaction product layer was observed on the surface of both alloys, and was analyzed using an X-ray diffraction (XRD), Auger electron spectroscopy (AES) and X-ray Photoelectron spectroscopy (XPS). The layer was comprised of two phases, which were outer oxide layer (mainly Ti02) and inner nitride layer (mainly TiN or Ti 2N). In these layers, the thickness of the oxide layer particularly depended on the kinds of alloys. According to the thermodynamics and point defect theory, the growth rate of oxide layer is expected to be increased by the presence of Al in TiO2. Namely, the dissolution of Al into TiO 2 may increase the number of oxygen vacancies, resulting in acceleration of oxygen diffusion inward. On the other hand, the elements that accelerate the growth of the oxide layer are not contained in TNTZ. Thus, the oxide layer formed on Ti64 was thicker than that of TNTZ. In a similar way, the elements that accelerate the growth of the nitride layer are not contained in both TNTZ and Ti64. Thus, the nitride layers with similar thicknesses may be formed on TNTZ and Ti64 during gas nitriding.

Original languageEnglish
Pages (from-to)415-422
Number of pages8
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Volume71
Issue number4
DOIs
Publication statusPublished - Apr 1 2007
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

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