The diffusion behavior of elements in Hastelloy C-276 (C, Si, Mn, Co, W, Fe, Cr, Mo, Ni) in alumina films was investigated by using secondary ion mass spectroscopy. The films were deposited by ion-beam-assisted deposition and annealed in vacuum at 500 to 1000C. Characterization of film microstructure was performed by using transmission electron microscopy and selected area diffraction analyses. The films were predominantly amorphous with alumina nanocrystallites non-uniformly dispersed throughout the volume both before and after annealing. A relatively wide interface region between the Hastelloy substrate and alumina film was formed in the as-deposited sample due to ion beam mixing. No diffusion of any of the substrate elements was observed after annealing, except for Mn, Cr, and Ni. The impurity depth distributions consisted of 2 components, which differed by several orders of magnitude with respect to diffusion coefficient and solubility. The activation energies and temperature dependences of the diffusion coefficients were determined.

Characteristics of Alumina Diffusion Barrier Films on Hastelloy. I.Usov, P.Arendt, L.Stan, R.DePaula, H.Wang, S.Foltyn, P.Dowden: Journal of Materials Research, 2004, 19[4], 1175-80

Table 43

Diffusion of Cr in Alumina Monocrystals