A Quantified Study of the Resistance of Duplex Stainless Steels to HISC: Part 2–Significance of the Hydrogen Permeation Properties and Severity of Stress Raisers on Hydrogen Transport and Cracking

The quantified microstructural analysis performed on a wrought and a hot isostatically pressed UNS S31803 duplex stainless steel (DSS) in the Part 1 publication of this study established the significance of the three-dimensional (3D) distribution and morphology/geometry of the ferrite and austenite phases on hydrogen transport through two DSS product forms (see Blanchard, et al., Corrosion 78, 3 [2022]: p. 249–257). This paper is a follow-up to Part 1 and focuses on the role of the other two key, interrelated components of hydrogen-induced stress cracking (HISC): stress/strain and hydrogen. For this purpose, experimental hydrogen permeation measurements, and environmental fracture toughness testing (i.e., J R-curve testing) using conventional and nonstandard single-edge notched bend test specimens were used. These particularly enabled interpretation of the hydrogen permeation and transport test data, and evaluation of suitability of environmental fracture toughness test methods for the assessment of resistance to HISC in DSSs. The latter is discussed, both from laboratory and component integrity perspectives, in the context of the findings from the 3D microstructural characterization of the two phases, the role of stress raisers and their severity, and hydrogen transport through the bulk and from the surface.