The history and development of a new SOHIC test method

Stress Orientated Hydrogen Induced Cracking (SOHIC) has been the mechanistic cause of a number of pipeline and pressure vessel failures, operating under sour service conditions. The crack morphology is now recognized in NACE MR0175/ISO 15156 as being caused by an independent mechanism. Within the Testing Appendix the standard says “other test methods under development can be used,” such a method is now available. Previous test method NACE TM0103, published by NACE, has now been with drawn. This paper will follow the history of SOHIC, the development of a new small-scale, short duration test method, and the possible relationship with hardness and microstructure. Now that a true test method is available, the mechanism of SOHIC can now be better studied and understood. Finally, the control of yield strength and ferrite hardness by use of niobium will be considered. (AU) © CBMM