Assessment of Ternary Multicomponent Diffusion in Alloy 22 (Ni-Cr-Mo)
Diffusivity [D] matrices are reported for the ternary Ni-Cr-Mo alloy in the approximate single-phase compositional range of Hastelloy C-22 (Alloy 22), surrounding Ni-63 wt.%, Cr-22.3 wt.%, and Mo-14.7 wt.%. These data will contribute to our understanding of the long-term phase stability of Alloy 22, and its potential use as a corrosion barrier in nuclear waste packages. Experimental diffusion couple data were obtained at selected temperatures from a series of diffusion couples, and evaluated, assuming constant diffusivity. Our approach treats the process as an optimization problem that simultaneously considers concentration profile data from numerous diffusion couples surrounding a single end-point composition. We make use of the mathematical characteristics of the analytical solution to this problem, reducing the number of parameters to be fitted. The parameter fitting is accomplished using a combination of heuristic and deterministic methods. Discussion of the sources and magnitudes of uncertainty in the diffusivity values is included.
Prof. Yong Ho Sohn, C. Campbell, D. Lewis and Afina Lupulescu
A.V. Jaques and J.C. LaCombe, "Assessment of Ternary Multicomponent Diffusion in Alloy 22 (Ni-Cr-Mo)", Defect and Diffusion Forum, Vol. 266, pp. 181-190, 2007