Determination of apparent diffusivity of hydrogen in 9Cr-1MoVNbN steel using hot extraction-PEMHS technique

In the present study, apparent diffusivity of hydrogen at different temperatures in 9Cr-1MoVNbN steel was determined using the data obtained from the measurement of hydrogen evolved from specimens charged with hydrogen. Cylindrical specimens of the 9Cr-1MoVNbN steel in normalized condition were charged with hydrogen electrochemically to saturation level. Hot extraction technique was used for collection of hydrogen evolved from the specimens at different temperatures in a chamber. Subsequently, measurement of evolved hydrogen was carried out using a Nafion based proton-exchange-membrane hydrogen sensor (PEMHS). Using these data in the diffusion equation for a finite cylinder, apparent diffusivity of hydrogen in steel was determined at temperatures in the range of 25-400 °C. Hydrogen lost from the specimens prior to start of the collection of hydrogen evolved was estimated. Apparent diffusivity data, earlier obtained, were revised by considering this lost hydrogen in the estimation. Apparent diffusivities calculated using this method agreed well with the values reported in the literature.