Mohammad Ali Mohtadi Bonab

In this research, the effect of important parameters on hydrogen affected fatigue failure in pipeline steel was studied in detail through literature review. It was found that several parameters including steel microstructure, load frequency, temperature of test environment, hydrogen pressure and stress intensity factor range may influence fatigue phenomenon in pipeline steels in hydrogen environment. It was also found that the pearlite microstructure slows down fatigue crack growth rate. The hydrogen effect on the fatigue crack growth rate is more pronounced by migrating the hydrogen atoms to the crack tip at low frequencies. The fatigue crack growth accelerates with the increase of hydrogen pressure and its minimum amounts are observed when tested in the air. Micro-cracks and some large cracks is observed in the fracture surfaces in fatigue tested specimens in hydrogen environment showing that the interaction of cyclic loads and hydrogen makes pipeline steel highly susceptible to cracking.