Postweld electrotransport treatment

Abstract

Hydrogen damage susceptibility of high-strength steel weldments and in other advanced materials, such as intermetallics, is a problem that restricts their application in many structural uses. A high-temperature (~500 °C) postweld treatment is often applied to remove the diffusible hydrogen and make the material more resistant to hydrogen damage. An electrotransport technique, using a direct current, can be applied at room temperature to move hydrogen from the underbead region, which is crack susceptible. The method has been used to electrorefine many metals and alloys containing both interstitial and substitu-tional solutes. This paper reviews the electrotransport theory and applies it to estimate the time of electrotransport treatment for lowering the hydrogen content from the underbead region by 50%. Thus, this theoretical work forms the basis for developing a new practice and provides sample calculations. Under a combined influence of the diffusional and electrotransport at room temperature using an electric field of 0.10 V/cm, ~30 min is required to remove 50% of the hydrogen from a starting concentration of 5 ppm. Theoretically, the treatment will also generate a heat of 0.95 kcal/s, which may not cause an excessive temperature increase in the workpiece. The electrotransport technique thus has the potential for a low-cost, low-temperature practice for mitigating hydrogen damage susceptibility.