High-pressure Hydrogen Environment Research Articles

Effects of gaseous hydrogen on fatigue crack growth in pipeline steel

The effects of hydrogen on crack growth rates in a moderate-strength pipeline steel subjected to cyclic loads were studied. Fatigue crack growth experiments were conducted in high-pressure hydrogen and nitrogen environments, and the influences of stress ratio, stress intensity, and cyclic loading frequency on hydrogen-accelerated fatigue crack growth were investigated. Hydrogen acceleration of intermediate-rate (Stage II) crack growth was greatest at low stress ratios and decreased to approximately zero at a stress ratio of about 0.5. However, hydrogen promoted the premature onset of accelerated (Stage III) crack growth. This appeared to be related to a hydrogen-induced reduction of fracture toughnessJIC.

Fracture Testing in High Temperature and Pressure Hydrogen Environments

Abstract Fracture mechanics tests were conducted on a 2¼Cr-1Mo steel in an environment containing 6% hydrogen sulfide and 94% hydrogen at temperatures up to 727 K (850°F) and pressures to 24.1 MPa (3500 psi). A test chamber and accompanying system were designed to test under monotonically rising, sustained, and cyclic loads. This paper contains a description of the design and operation of the system developed to conduct these tests, along with a brief discussion of testing experience and types of results.

The role of crack blunting in sustained load crack growth

Sustained load crack growth occurs in metals following critical crack extension above KIc and in aggressive environments while maintaining a constant load below KIc. In this paper, crack arrest measurements are performed on precracked, 0.0254-m thick, side-grooved WOL specimens exposed to 34.5 MN/sq m hydrogen at ambient temperature. The specimens are loaded inside a pressure vessel while in contact with the high pressure hydrogen environment. Crack growth is observed with each loading increment. The crack blunting observed in the fracture mechanics tests on 321 stainless steel is found to be similar to that produced in the 321 stainless steel tensile specimens. Rounding and branching of the crack decreases the effective stress intensity at the crack tip. It is possible, for materials in which cracks tend to blunt or branch in hydrogen, that although cracks will arrest at a relatively high stress intensity in decreasing stress intensity test, a crack may begin to grow at a lower stress intensity when loaded in hydrogen, and the crack may continue to grow when the stress intensity is continually increasing.

Creep and Rupture Behavior of Low Alloy Steels in High Pressure Hydrogen Environment

The creep and rupture properties of steels were investigated at 1000 deg F in an environment of argon at 50 psig pressure and hydrogen at 900 psig pressure. An SAE 1020 steel, a 0.5 percent Mo-steel, and a 1 percent Cr-0.5 percent Mo steel were used as test materials. The strength of the steels was lower and the creep rate higher in hydrogen than in argon. The data are discussed in respect to the effect of stress on the rate of hydrogen attack.