Diffusion of Ni⁶³ and W¹⁸⁵ in Nickel-Tungsten Alloys (On the Relation between High-Temperature Creep and Diffusion in Nickel Base Solid Solutions. III)

Abstract

The self-diffusion coefficients of nickel and tungsten in nickel-tungsten alloys containing 0 to 9 at%W have been measured with a usual lathe sectioning technique. Polycrystalline specimens having 1 to 4 mm grain size were used. Measurements were carried out over the temperature range from about 1100° to 1400°C. In this system, nickel atom diffuses more rapidly than tungsten atom, and the ratio of diffusion coefficient of nickel to that of tungsten is from 3 to 4 for each composition over the temperature range examined. Diffusion rates of both elements decrease with increasing tungsten contents. The frequency factors for nickel self-diffusion are 1.9, 30, 58 and 1.1 cm²/sec, and the activation energies are 68.0, 76.5, 80.6 and 70.3 kcal/mol for alloys containing 0, 1.7, 5.3 and 9.2 at% tungsten, respectively. For tungsten self-diffusion in respective alloys, the frequency factors obtained are 2.0, 2.2, 17 and 1.4 cm²/sec, and the activation energies are 71.5, 73.1, 80.5 and 74.5 kcal/mol.