Abstract
Precise measurements of hydrogen permeation through highly purified iron have been performed utilizing the gaseous permeation technique with the hydrogen pressure ranging between 0.001 and 0.1 MPa in a wide temperature range from 420 to 1100 K. The effect of surface oxide and/or lattice imperfections on hydrogen transport has also been investigated by changing the impurity level of hydrogen gas or by introducing the lattice imperfections due to deformation of the specimen without any change in other factors. Obtained values of permeability (Φ) and diffusivity (D) are 2.88×10−5exp(−32.12kJ·mol−1⁄RT) mol/m·s·MPa1⁄2 and 6.04×10−8exp(−6.99kJ·mol−1⁄RT) m2/s, respectively. The hydrogen solubility in iron is calculated from these quantities to be 4.77×102exp(−25.14kJ·mol−1⁄RT) mol/m3·MPa1⁄2.
Values of Φ are found to be reduced by sample deformation probably due to hydrogen trapping by lattice imperfections produced by the deformation. Both Φ and D are also found to be reduced due to surface oxidation by impurity water vapor or oxygen included in hydrogen gas at temperatures below 500 K, and the reduction of D is more pronounced than that of Φ.
