Stress Oriented Hydrogen Induced Cracking Behavior of Carbon Steel in Wet H2S Environment

The stress oriented hydrogen induced cracking (SOHIC) behavior of L360QS steel, which is very common carbon steel used in the oil industry was investigated according to NACE TM 0103. The stress concentration factor and inhomogeneous microstructure, which have a great influence on the SOHIC behavior of carbon steel, were considered in this paper. The results showed that SOHIC crack was a special kind of hydrogen induced cracking. The typical SOHIC was composed of planar crack and longitudinal crack. When the stress concentration factor exceeded 6.3, the cracking susceptibility increased. The inhomogeneous microstructure in the carbon steel would supply places for hydrogen, and huge hydrogen pressure would generate planar crack. Longitudinal crack was influenced by tensile stress and hydrogen pressure. The analysis of fracture morphology showed no dimple,indicating that typical stress oriented hydrogen induced cracking was a kind of brittle fracture.