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| ELECTROCHEMICALLY SURFACE ALLOYING ON Ni WITH Ta AND Nb IN MOLTEN FLUORIDES AND PROPERTIES OF Ta-Ni AND Nb-Ni ALLOYS |
| by QIAO Zhiyu(Beijing University of Iron and Steel Technology); Pieere TAXIL (Universite Paul Sabatier; Toulouse; France)(Manuscript received 9 January; 1986; revised manuscript 3 July; 1986) |
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Cite this article:
by QIAO Zhiyu(Beijing University of Iron and Steel Technology); Pieere TAXIL (Universite Paul Sabatier; Toulouse; France)(Manuscript received 9 January; 1986; revised manuscript 3 July; 1986). ELECTROCHEMICALLY SURFACE ALLOYING ON Ni WITH Ta AND Nb IN MOLTEN FLUORIDES AND PROPERTIES OF Ta-Ni AND Nb-Ni ALLOYS. Acta Metall Sin, 1987, 23(2): 198-205.
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Abstract The electrochemically alloying on Ni surface with Ta and Nb was carried out In molten LiF-NaF-K_2TaF_7 or LiF-NaF-K_2NbF_7 at temperatures between 850 and 1050℃. In both cases only TaNi_3 and NbNi_3 stable phases are detected in the bulk of the layer. The intermetallic compounds of Ta-Ni binary system, including Ta_2Ni, TaNi, TaNi_2 and TaNi_3 have been identified and the Gibbs energy of formation of Ta-Ni compounds have been calculated. It is shown that the growth of the surface alloying layer follows a parabolic law versus the alloying time. The kinetic parameters of the intermetallic diffusion of Ta-Ni and Nb-Ni systems, including the dimensionless parameters which depends on the solid compositions at the boundary of the alloy layer and the intermetallic diffusion coefficients D have been estimated by combination of electrochemical measurements and diffusion equation. The following equations are confirmed: x~2=Kt and α=(K/D)~(1/2) where x is the thickness of the surface layer and K is the constant.
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Received: 18 February 1987
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