Hydrogen in Metals: A Systematic Overview

Abstract

Abstract Hydrogen can damage metallic components in very different ways. In liquid phase metallurgical processes such as casting and welding, as a result of the dramatic reduction in the solubility of gases on solidification, gas bubbles can form causing porosity which particularly in conjunction with Hydrogen induced cracking, form “fish-eyes“ acting as dangerous internal stress raisers. This type of cracking, without the presence of porosity, which is also known as “flaking“, can occur equally in thin steel wires only a few μm in diameter and in large 100 tonne steel forgings, in both cases significantly detrimentally affecting both the manufacturing and service behaviour of the component. Apart from metallurgical sources, semi-finished and finished components can also absorb Hydrogen from galvanic processes and as a result of corrosion. In these cases the Hydrogen diffuses into regions of higher stress and strain causing cracking, often unexpectedly and after significant periods of time.