Anomalies in hydrogen enhanced fatigue of a high strength steel

Fatigue crack growth for an HSLA steel was studied with in situ hydrogen charging. The hydrogen effect was highest at low ΔK values. The anomalies in hydrogen effect were found in the relative insensitivity of the crack growth rates to ΔK in a decreasing ΔK test protocol, and in the distinct differences of the crack growth rates for different loading protocols. These anomalies are explained by the hydrogen availability at the crack tip as a function of the test parameters. A “t” and “ΔK” based parameter was found to be universally applicable for hydrogen enhanced fatigue irrespective of loading protocol.