Fatigue crack growth behaviour of 4130X steel in H₂S environment

Abstract

Fatigue crack growth rates of 4130X steel used for compressed natural gas vessels were investigated in this paper. Considering the operating conditions, corrosion fatigue tests at a low frequency of 0?0067 Hz, in H 2 S saturated, H 2 S unsaturated and air environments were conducted on modified wedge opening load specimens by using a home made low cycle fatigue test system. Curve fitting was applied to the fatigue test data of da/dN-DK according to Paris formula. A correlation study between fracture surface and stress intensity factor range was conducted and K values for three stages in different environments were characterised quantitatively. The results show that da/dN in H 2 S environment is more than 20 times faster than in an air environment. When the H 2 S concentration reaches a certain range, the increase of da/dN becomes slower than that of the H 2 S concentration. da/dN differs by 2?4 times while the concentration differs by 11 times. The corrosive environment accelerates the fatigue failure.

Fatigue behavior of hydrogen pre-charged low alloy Cr–Mo steel

“…In the papers [20] and [28] AISI 4130 specimens were fatigue tested in H 2 S aqueous solution with similar test parameters. These authors found analogous curves of the crack growth rate.…”