Application of a tritium imaging plate technique to depth profiling of hydrogen in metals and determination of hydrogen diffusion coefficients

Abstract

A new methodology for depth profiling of hydrogen in metals is developed applying a tritium imaging plate technique (TIPT) with cross sectional observation. Owing to its high sensitivity and wide dynamic range for tritium detection, depth distribution of hydrogen dissolved in the BCC metals such as tungsten (W) and steels are successfully obtained. The depth distributions enable us to determine reliable lattice diffusion coefficients of hydrogen in W and a ferritic/martensitic steel (F82H) within 20% errors taking into account three dimensional desorption/ release from the surfaces of the sample metals. Hydrogen trapped at surface and subsurface are clearly separated from the dissolved one. In BCC metals, since the former could be much larger than the latter, observation of overall hydrogen behavior without knowing detailed depth distributions could lead to wrong estimation of diffusion coefficients and solubility.