Fatigue Behavior Of Pipeline Steel Under Hydrogen Environment And Low Temperature

AbstractIn the presence of H2S, metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. In this paper the influence of hydrogen and low temperature on mechanical properties of two pipeline materials, X65 micro-alloyed and F22 low alloy steels, is studied. An electrochemical hydrogen charging method has been setup. Diffusible hydrogen content of steels is in the range 0.6 to 2 ppm. Fatigue propagation tests were carried out on charged and uncharged specimens, by varying the test temperature and the frequency of the load application cycle. The experimental results show an evident effect of the hydrogen presence on the fatigue crack growth. The diffusion rate of hydrogen in the steels seems to be the most important parameter in order to explain the influence of temperature and frequency on the fatigue crack propagation rate. Fracture surface examination confirms the results of mechanical testing