Abstract
The sour gas susceptibility of X-80 steel was investigated after quenching and tempering. Self-loaded modified wedge opening loading (M-WOL) specimens were exposed to an NACE sour gas solution under an applied opening mode stress intensity factor KI of 40 MPa m1/2 In this microstructural condition, crack arrest was exhibited at a threshold stress intensity value (KISSC) of 32 MPa m1/2. The relatively good performance of the steel after quenching and tempering was closely related to the development of a fine distribution of (Nb, Ti) containing carbides along ferrite lath boundaries. Apparently, the main crack path exhibited a significant number of bifurcations as it shifted continuously to follow the ferrite interlath boundaries as well as the prior austenitic grain boundaries.
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