Stress oriented hydrogen induced cracking

Stress-oriented hydrogen-induced cracking (SOHIC). 

Figure 7.84 Stress-oriented hydrogen-induced cracking in linepipe (x 50) (Courtesy of Malcolm Hay)...

W. Bruckhoff, O. Geier, K. Hofbauer, G. Schmitt, D. Steinmetz. Rupture of a Sour Gas Line Due to Stress Oriented Hydrogen Induced Cracking - Failure Analyses, Experimental Results and Corrosion Prevention. NACE Corrosion/85, Paper 389, Boston, USA, 1985-03-25/29. 

A special form of HIC that occurs in low-strength steels in the presence of a stress is stress-oriented hydrogen-induced cracking (SOHIC) [127,130,131]. It is characterized by the formation of a stacked array of hydrogen-induced cracks, as shown in Figs. 16 and 17. These small cracks are oriented parallel to the rolling direction, but the stack itself is perpendicular to the stress. The cracks become hnked by transgranular cracks to produce an overall crack perpendicular to the stress. 

The presence of tensile stress in the component may cause individual ligaments of HIC to form a stack of through-thickness array. This is a necessary precursor to stress-oriented hydrogen-induced cracking (SOHIC). SOHIC is common in heat affected zones (HAZs) of welds in low-strength steels. 

A. Takahashi, H. Ogawa, Influence of microhardness and inclusion on stress oriented hydrogen induced cracking of line pipe steels, ISIJ Inti. 36 (1996) 334-340. 

Figure 8.14. (a) Hydrogen-induced cracking (H.I.C.). (b) Stress-oriented hydrogen-induced cracking (S.O.H.I.C.). (Courtesy of Malcolm Hay.)... 

Figure 3-17a. Stress-oriented hydrogen-induced cracking (SONIC) from pre-existing sulfide stress cracking (SSC). API, 19 ...

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