TY - JOUR
T1 - 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
AU - Nakai, Masaaki
AU - Niinomi, Mitsuo
AU - Akahori, Toshikazu
AU - Ohtsu, Naofumi
AU - Nishimura, Hideki
AU - Toda, Hiroyuki
AU - Fukui, Hisao
AU - Ogawa, Michiharu
PY - 2007/4/1
Y1 - 2007/4/1
N2 - 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.
AB - 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.
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U2 - 10.2320/jinstmet.71.415
DO - 10.2320/jinstmet.71.415
M3 - Article
AN - SCOPUS:34249784501
SN - 0021-4876
VL - 71
SP - 415
EP - 422
JO - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
JF - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
IS - 4
ER -