A Proposed Mechanistic Approach to Investigate the Susceptibility of Super Martensitic Stainless Steels to Sulfide Stress Cracking

摘要

Super martensitic stainless steels are widely used in oil & gas production environments) for mitigation of general corrosion due to the presence of CO_2 in the produced fluids providing a cost-effective alternative to more expensive corrosion resistant alloys (CRA. However, there is little agreement on service limits when exposed in environments that contain H_2S, particularly in relation to the susceptibility to sulfide stress cracking (SSC). This paper presents a review of published literature regardingsusceptibility to SSC of super martensitic stainless steels in production environments, with the aim to evaluate the service limits of these materials from both the empirical and mechanistic approaches. The conclusion of this review is that an adequate assessment of the susceptibility to SSC can only be accomplished using testing methods that account for both the role of the passive layer and the formation of metastable pits and their propagation in H_2S-containing environments. This paper recommends the characterization of the passive layer resistance in super martensitic stainless steels using point defect modeling techniques to identify the role of critical variables on pit induction time distribution to describe the susceptibility to SSC. These critical variables include material conditions such as stress and environmental conditions such as temperature. The methodology is described in detail and a recommended path for investigation is discussed.