Abstract
Supermartensitic stainless steels (SSS) have been applied in oil and gas industries for flowline material as an alternative for both duplex stainless steels and carbon steels with inhibitor. SSS show greater toughness, corrosion resistance and weldability properties when compared to conventional martensitic stainless steels. However, when protected cathodically in seawater environment they can be susceptible to hydrogen embrittlement due to hydrogen charging. The present study evaluates the fracture toughness of SSS submitted to cathodic protection in seawater environment at a potential of steel “over-protection”. Incrementally step loading technique was used in the SSS fracture toughness evaluation. The results show a significant drop in the fracture toughness of steel in the studied environment.Key words: supermartensitic stainless steel, cathodic protection, fracture toughness.
Highlights
The current increasing in oil and gas production from deeper wells impose more severe and deleterious operation conditions over the material used in the petroleum industry (Ramirez, 2007; Miyata et al, 2006)
A re-austenitization of steel at 1000oC for 30 minutes followed by air quench resulted in some reduction of ferrite phase, reported studies showed that the dissolution of δ-ferrite appear to be a slow process at solution temperatures (Carrouge et al, 2004)
The studied stainless steels (SSS) showed susceptible to hydrogen embrittlement when submitted to cathodic protection at a condition of over-protection in seawater environment
Summary
The current increasing in oil and gas production from deeper wells impose more severe and deleterious operation conditions over the material used in the petroleum industry (Ramirez, 2007; Miyata et al, 2006). Low carbon martensitic stainless steels, called supermartensitic stainless steels (SSS), have been developed for flowline applications in CO2 content environments contributing to oil and gas industries as an alternative to replace expensive duplex stainless steels or carbon steels with inhibitors (Miyata et al, 2007). The SSS combine low carbon content together nickel and molybdenum additions uniting, high corrosion resistance and good weldability in order to achieve superior properties in relation to conventional 13%Cr steels (Marchebois et al, 2007). Many studies have been carried in order to establish a better knowledge about SSS behavior and the viability of their application in oil and gas transport (Rogne et al., 1999)
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