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Mechanisms of Hydrogen Induced Stress Crack Initiation and Propagation in Super Duplex Stainless Steels
Author(s) -
Chai Guocai,
Ronneteg Sabina,
Kivisäkk Ulf,
Peng Ru Lin,
Johansson Sten
Publication year - 2009
Publication title -
steel research international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.603
H-Index - 49
eISSN - 1869-344X
pISSN - 1611-3683
DOI - 10.2374/sri09sp042
Subject(s) - materials science , duplex (building) , metallurgy , hydrogen , stress (linguistics) , composite material , chemistry , dna , biochemistry , linguistics , philosophy , organic chemistry
Austenitic and ferritic duplex stainless steels, DSS, have recently suffered from hydrogen stress induced cracking, HISC, in subsea components with a cathodic protection. This paper provides discussions on possible HISC mechanisms. HISC initiation can occur at the ferritic grain boundaries and phase boundaries at a stress lower than the yield strength, but dominantly at phase boundaries at a stress higher than the yield strength. EBSD analysis shows that HISC in DSS results from the interaction between the dynamic plasticity by creep and hydrogen diffusion. A model on the formation of microstresses in these two phases under creep conditions is proposed, which explains why HISC occurs mainly in the ferritic phase. Discontinuous two‐dimensional HISC paths were observed. The austenitic phase acts as obstacles for crack propagation. The fracture covers “valleys” and “peaks” with the cleavage ferrite and the austenite with microfacets or striations due to the hydrogen‐enhanced localized‐plasticity.