The Effect of Hydrogen Gas on Tensile and Fatigue Properties of High Strength Carbon Steels

This study investigates the impact of hydrogen gas on the tensile and low cycle fatigue (LCF) properties of two high strength steels by means of the hollow specimen method. The steels studied have ultimate tensile strengths in the range of 530 to 650 MPa, and ferritic-pearlitic and bainitic microstructures, respectively. The behaviour of these steels was evaluated in a pressurized environment containing either inert gas (Ar) or hydrogen (H 2 ) at room temperature and a pressure of 200 bar. The findings of this work indicate that hydrogen has a detrimental effect on the ductility and reduction in area, while the other tensile properties remain unaffected for both steels. Hydrogen uptake due to the interaction between H 2 and steel during mechanical testing was measured. The fractographic analysis revealed presence of brittle fracture and embrittlement despite that the tensile properties of the steels were not affected. In contrast, the fatigue life of both steels was severely affected by H 2 compared to Ar environment when tested at high strain amplitudes. The fractographic inspection of the LCF tested specimens indicated differences in crack propagation behaviour between Ar and H 2 environment. Specimens tested in H 2 indicated faster crack growth and widely spread striations. Finally, this work concludes that the bainitic steel exhibits slightly better mechanical performance than the ferritic-pearlitic steel in pressurized hydrogen gas for the respective testing conditions.