SEDL / STP / STP962-EB / STP45297S

Sensitivity of Steels to Degradation in Gaseous Hydrogen

Cialone, Henry J.
Senior research scientist and section manager, Physical Metallurgy Section, Battelle, Columbus Division, Columbus, OH

Holbrook, John H.
Senior research scientist and section manager, Physical Metallurgy Section, Battelle, Columbus Division, Columbus, OH

Pages: 19    Published: Jan 1988

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Abstract

Sensitivity of API-5L X42 and X70 line-pipe steels to hydrogen degradation of fracture properties has been studied under a variety of loading conditions. Hydrogen-enhanced crack growth under fatigue and static loading was evaluated in numerous hydrogen-rich gas mixtures. Under cyclic loading, hydrogen accelerated fatigue-crack growth, depending on frequency, stress ratio, stress-intensity range, and composition of the gas mixture in the environment. Under static load, subcritical-crack growth has been shown to occur in high-strength steels, in weld heataffected zones, and in steel heat treated to simulate local hard regions in pipeline steels, J-integral fracture-toughness experiments have shown that hydrogen reduces the fracture toughnessJ^lc, and, in steels that undergo subcritical-crack growth, reduces the tearing resistance, dJ/da. A relationship between hydrogen-accelerated fatigue-crack growth and hydrogen-induced reductions in fracture toughness is presented. The reduction or elimination of hydrogen-degradation effects by the presence of certain inhibitor gases, such as oxygen (O²), carbon monoxide (CO), or sulfur dioxide (SO²), also is discussed.