Permeation, Diffusion, and Solution of Nitrogen in Tungsten and Molybdenum

Abstract

Using ultrahigh-vacuum and mass-spectroscopic techniques, permeation, diffusion, and solution of nitrogen in W and Mo have been measured for pressures between 5 × 10−5 and 500 torr and for temperatures between 1100° and 2500°K. The following values for the permeation constants, P(torr·liter/cm·sec·torr1/2), diffusion constants, D (cm2/sec), and solubility constants, S(torr·liter/cm3·torr1/2), are obtained: P(W) = 1.6 × 10−4exp (− 52 000 / RT); P(Mo) = 6.1 × 10−3exp (− 47 500 / RT); D(W) = 5.4 exp (− 62 000 / RT); D(Mo) = 2.3 × 10−2exp (− 33 000 / RT); S(W) = 3.0 × 10−5exp (+ 10 000 / RT); S(Mo) = 2.6 × 10−1exp (− 14 500/RT). For nitrogen in Mo, the diffusion constant is in agreement with Zener's theory of interstitial atomic diffusion. For nitrogen in W, the frequency factor of the diffusion constant and the diffusion activation energy are abnormally high and not in agreement with Zener's theory.