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.
The Long-Term Corrosion Performance of Alloy 22 in Heated Brine Solutions