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Picture for Effect of Ni on Sulfide Stress Cracking and Stress Grooving in Carbon Steel - Part 1: Constant-load (Dead-weight) Test

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Effect of Ni on Sulfide Stress Cracking and Stress Grooving in Carbon Steel - Part 1: Constant-load (Dead-weight) Test

Product Number: 51324-20715-SG

Author: Taishi Fujishiro; Taro Muraki; Nobuyuki Ishikawa; Daichi Izumi; Takuya Hara

Publication Date: 2024

$40.00

Sulfide stress cracking (SSC) occurs in steel exposed to sour environments. Ni promotes the formation of a crack-like corrosion morphology (so-called stress groove or fissure), which accelerates the SSC; however, the mechanisms underlying fissure formation and growth are not fully understood. In this study, the effects of Ni on SSC and fissures were investigated. Constant-load tests were conducted at various potentials using TS 800 MPa grade steel with and without 1 % Ni addition. The fissures were formed near the corrosion potential on adding Ni. Anodic or cathodic polarization promoted SSC, suggesting that SSC was affected by both active path corrosion (APC) and hydrogen embrittlement (HE) mechanisms. In addition, the fissure shapes and crystal orientations of the microstructure were analyzed to classify the fissures as dissolution (corrosion) or mechanical cracking. Further, characteristic grooves promoted by Ni were confirmed to be APC.

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

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

Product Number: 51324-20709-SG

Author: Nobuyuki Ishikawa; Taishi Fujishiro; Eiji Tada; Daichi Izumi; Junji Shimamura

Publication Date: 2024

$40.00

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.

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