Effect of Hydrogen on Grain Boundary Diffusion of Chromium in Zr–1 wt % Nb Alloy

Comparative studies of chromium grain boundary diffusion in the near-surface layer of Zr–1Nb and Zr–1Nb–0.14Н polycrystalline alloys were conducted at isothermal diffusion annealing and irradiation of the surface with a pulsed electron beam (PEB) in the temperature range of 573–723 K. The optical emission spectrometry of high-frequency glow discharge was used to determine the distribution profiles of chromium concentration by depth in the near-surface layer of the studied alloys. The grain boundary diffusion parameter of chromium Pb = δsDb (δ is the grain boundary width; s is the segregation coefficient; and Db is the grain boundary diffusion coefficient) in the near-surface layer of Zr–1Nb and Zr–1Nb–0.14Н alloys was estimated based on the Whipple−Le Claire equation. It is revealed that at simultaneous exposure to temperature and PEB irradiation, the Pb parameter increases, while the activation energy of grain boundary diffusion of chromium in the near-surface layer of the Zr–1Nb alloy decreases. The presence of hydrogen in the Zr‒1Nb–0.14Н alloy results in a reduction of the Pb parameter and a rise in the activation energy of grain boundary diffusion of chromium.