The interdiffusion of C (originating from a graphite substrate) into a Nb coating and the fabrication of its carbides by heat treatment at 1073 to 1773K was studied. The thickness of the Nb2C and NbC phases formed after heat treatment as well as the interdiffusion coefficients for the formation of the carbide layers were also studied. It was found that the carbide layer growth exhibited parabolic behavior patterns inherent in the growth rate constants of Nb2C and NbC layers. By assuming that the interdiffusion coefficients were independent of concentration, it was possible to determine the interdiffusion coefficients of C into Nb2C and NbC layers as a function of temperature.

Interdiffusion of Carbon into Niobium Coatings Deposited on Graphite. S.Barzilai, A.Raveh, N.Frage: Thin Solid Films, 2006, 496[2], 450-6