CHEMICAL DIFFUSION OF NIOBIUM IN NICKEL

Although impurity diffusion values are of great interest in developing nickel base super alloys, limited data in 4d-transition elements are available. This paper reports on niobium diffusion data in nickel in t he temperature range between 1200 and 1500 K, obtained by using an ele ctron probe microanalyser. The temperature dependence of the diffusion coefficient, D-Nb, can be expressed by the following Arrhenius relati on, D-Nb = 1.04(-0.48)(+0.87) X 10(-6) exp[-(202.59 +/- 4.71 -0.48 kJ/ mol)/RT] m(2)/s. These studies have shown that the niobium diffusivity is nearly one order of magnitude higher than the self diffusivity in nickel. The large difference between the activation energy values (Del ta Q = -78.31 kJ/mol) indicates a rather high impurity-vacancy binding energy.