Effect of Ni on Sulfide Stress Cracking and Stress Grooving in Carbon Steel - Part 2: Four Point Bend Test

Four point bend sulfide stress cracking (SSC) tests were carried out under various conditions of H2S partial pressure, pH, soaking time, and applied stress to investigate the formation of stress groove (or fissure) and SSC behavior in TS 800 MPa (116 ksi) grade steel plates with 1%Ni added and 0% Ni steels. Under low hydrogen sulfide (H2S) partial pressure conditions, a fissure was formed only in the 1%Ni steel, although no SSC occurred. Morphology of the fissure in 1% Ni steel indicates that fissure extends by a corrosion, which is also called the anodic dissolution or the active path corrosion (APC). The fissure in 1%Ni steel grew almost linearly with soaking time in the test solution with stabilized pH condition. Formation and growth of fissure was enhanced by higher applied stress and there was a limiting stress for the formation of fissure. SSC occurred in both steels under high H2S partial pressure and low pH conditions. Detailed metallographic investigation for SSC cracks revealed that a corrosion pit initially formed then turned into a crack possibly by hydrogen embrittlement (HE), then finally caused unstable crack extension to rapture the specimen. Based on the experimental results for the fissure formation and SSC, the effect of both APC and HE are discussed.
Product Number: 51324-20709-SG
Author: Nobuyuki Ishikawa; Taishi Fujishiro; Eiji Tada; Daichi Izumi; Junji Shimamura
Publication Date: 2024