Abstract
In this work, four alloys were tested by means of the gas evolution permeation technique in order to determine the influence of the Cr content on the hydrogen diffusive transport parameters: pure Fe metal, Fe5%Cr alloy, Fe10%Cr alloy and Fe14%Cr alloy. The experimental measurements were performed over the temperature range of 423–823K and for high purity hydrogen loading pressures ranging from 1.0×104Pa to 1.5×105Pa. We observed that the permeability obtained for the pure Fe metal and for the two alloys containing 5% and 10% Cr follows an Arrhenius law in each case for this temperature range. For the alloy containing 14% Cr, two different Arrhenius fittings were needed: one for high temperatures (above 710K) and another one for low temperatures. In general terms, the increase in the Cr content in the alloy leads to smaller values of the permeability. Regarding diffusivity and Sieverts’ constant, trapping effects have been observed for the alloys containing Cr. These effects lead to a sudden decrease of the diffusivity together with an increase of the Sieverts’ constant at low temperatures. This phenomenon was detected at temperatures below 473K, 523K and 573K for the Fe5%Cr alloy, Fe10%Cr alloy and Fe14%Cr alloy, respectively. According to the results, the influence of the metallurgical composition of Cr in Fe alloys on the transport parameters and trapping of hydrogen is discussed.
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