Effect of Retained Austenite on the Hydrogen Permeation Behavior in High Strength Steels

Abstract

The permeation behaviors of hydrogen in high strength steels with and without retained austenite were studied by means of electrochemical method. The diffusivity obtained from the permeation curves was smaller and activation energy was larger in steels with retained austenite than those without retained austenite. The hydrogen permeation curves in steels without retained austenite agreed well with theoretical permeation curves, obtained from the assumption of diffusion in homogeneous steel. However, the permeation behavior of hydrogen in steels with retained austenite consisted of two permeation curves. The first curve indicated the permeation in ferrite phase and the second one was that in ferrite and austenite phases or ferrite/austenite interfaces. The apparent diffusivities decreased with the amount of retained austenite but the diffusivities in the first stage agreed well with those without retained austenite in the similar strength steel.