A Study of the Effect of Voids on Hydrogen Diffusion Through Electroslag Refined Steel

Disk-shaped thin specimens made of electroslag refined (ESR) carbon steel were treated with hydrogen at 758 kPa (450 psi) at 600°C for 120, 240, or 432 h to produce microvoids (from methane bubbles) with a diameter of about 0.1 γm and a volume fraction up to 0.2%. Using the two-step replica technique, the size and density of voids were measured. The hydrogen diffusion coefficients of these specimens were determined by an electrochemical permeation method. Different charging current densities were used. The microvoids serve as traps for hydrogen as indicated by the hydrogen diffusion coefficient decreasing as the current density and the void density increased.