THE USE OF A PERMEATION TECHNIQUE TO PREDICT CRITICAL CONCENTRATION OF H-2 FOR CRACKING

Hydrogen induced cracking (HIC) of steel is shown to occur when the amount of hydrogen is greater than a critical concentration, C//K. A technique is proposed in order to compute this critical concentration, based on the conventional electrochemical permeation technique. The C//K value comes from a knowledge of diffusible, reversibly trapped and irreversibly trapped concentrations of hydrogen. The experimental results obtained are compared to data gathered from more conventional tests (chemical analysis, mechanical testing). Results obtained on three kinds of material are discussed and practical interest of the knowledge of C//K is underlined.