Analysis of the Applicability of the Hydrogen Permeation Method for Determining the Terminal Solid Solubility of Hydrogen in Hafnium

Many structural metallic materials (in particular, hafnium, zirconium, and titanium alloys) exploited in hydrogen-containing media tend to form brittle hydride phases when absorbing hydrogen, which deteriorates their mechanical properties. Determination of the terminal solid solubility (the hydrogen concentration in a metal at which hydride formation occurs) is an important and time-consuming experimental task. The purpose of this study is to develop a new approach based on the hydrogen permeation method, which makes it possible to find the terminal solid solubility at isothermal saturation without using an expensive equipment. The technique is based on the change in the character of hydrogen permeation through a membrane from a material studied as a result of the hydride phase formation; this technique imposes certain limitations on the experimental conditions. They are related to the parameters of the surface and bulk processes of hydrogen interaction with the material. The importance of the correct choice of experimental conditions for determining the terminal solid solubility of hydrogen in metals was demonstrated using computer simulation, the possibility of applying the technique to hafnium was analyzed, and the protocol and parameters of the experiment were substantiated.