The decarburization behavior of Nb wires was studied at 1600 to 2120C. The results could be explained by a C diffusivity of the form:

D (cm2/s) = 1.8 x 10-2 exp[-38.0(kcal/mol)/RT]

G.Hoerz, K.Lindenmeier: Zeitschrift für Metallkunde, 1972, 63[5], 240-7