Hydrogen Induced Delayed Failure of High Strength Alloy Steel Wires

Delayed failure tests, in which the samples were cathodically charged with hydrogen while under sustained tensile loads, were conducted upon two medium carbon alloy steels which had been quenched, tempered, and cold drawn to very high strength levels. The results were correlated with the microstructure and fractographic features of the steels. The resistance of the steels to hydrogen degradation is attributed to trapping of hydrogen on defects, alignment of elongated dislocation cell walls with the wire axis and decreased transverse wall spacing, all effects which are accentuated by increasing drawing strain. The beneficial effects of increased strain are thought to be limited eventually by the formation of internal fissures and voids.