Notch sensitivity and short cracks tolerance in a super 13Cr stainless steel under sulfide stress corrosion cracking conditions

Abstract

Abstract Notch sensitivity under sulfide stress corrosion cracking (SSC) conditions is quantified in this work, considering its tolerance to short cracks that start at notch tips and become non-propagating after growing for a short while. The considered material is an UNS S41426 super 13Cr5Ni2Mo martensitic stainless steel, frequently used in pipelines to transport aggressive fluids in offshore applications. Tolerance to short SCC cracks depends on the notch size and shape, on the stress gradient ahead of its tip, and on basic material resistances to crack initiation SSSC and growth KISSC inside the aggressive environment. The proposed notch-sensitivity model can be a powerful and economical alternative design tool to substitute traditional pass/non-pass criteria normally used to choose materials for SSC and similar environmentally assisted cracking (EAC) service conditions. This model is validated by testing the steel into an aqueous solution of 100 g/L of Cl−, pH 4.0, 25 kPa of H2S, and 75 kPa of CO2, at 23 ± 2 °C. After measuring SSSC (461 ± 23 MPa) and KISSC (36.9 ± 0.6 MPa√m), short crack tolerance predictions are verified on notched specimens loaded under a peak stress at their tips σmax = 0.95⋅SY >> SSSC, where SY = 826 MPa is the yield strength of the tested steel.