Effect of K-rate and cathodic protection potential on fracture toughness of the super duplex stainless steel UNS S32750

Super duplex stainless steels (SDSS) have emerged in the last decade or so as a candidate material to withstand harsh oil and gas production environments. However, documented cases of failure due to hydrogen induced stress cracking (HISC) have raised some concerns. The aim of this investigation is to evaluate the effect of the cathodic protection potential and K-rate on the susceptibility of SDSS to HISC. The results indicated that although the susceptibility to HISC might appear unequivocal, the tests parameters should be carefully considered since they influence dramatically on the results produced. Indeed, for more cathodic electrode potentials stronger is the detrimental effect on fracture toughness while the influence of K-rate is rather weak. However, the influence of this latter parameter becomes more relevant when the applied electrode potential is less negative.