The diffusivity of N in Fe-Ni alloys was determined at 900 to 1100C by measuring de-nitrogenation in H (using a microbalance), after nitrogenation. The N diffusivity increased with increasing Ni content. The increase was small up to 10wt%Ni, but was considerable for Fe-20wt%Ni. The activation energy for N diffusion decreased with increasing Ni content. The N diffusivities could be described by:

10wt%Ni:     D (cm2/s) = 5.6 x 10-1 exp[-160(kJ/mol)/RT]

20wt%Ni:     D (cm2/s) = 1.32 x 10-1 exp[-132(kJ/mol)/RT]

H.J.Grabke, E.M.Petersen: Scripta Metallurgica, 1978, 12[12], 1111-4