Abstract

The corrosion resistant alloys (CRAs) have been widely used as line pipes because of their corrosion resistance, availability and workability. They are used for flow the line material in corrosive wet gas-containing environments, i.e., containing carbon dioxide and hydrogen sulfide.

Recently, a new duplex stainless steel containing 25mass%Cr- 5mass%Ni- 1mass%Mo- 2.5mass%Cu has been developed. Chromium (Cr) and copper (Cu) are used because they can be considered as an alternative to molybdenum (Mo) in order to enhance the corrosion resistance. The developed material can provide sufficient sulfide stress cracking (SSC) resistance in slightly sour environment in spite of having lower Mo content than in existing duplex grades such as UNS S31803 (22Cr conventional duplex stainless steels). Post weld heat treatment (PWHT) is mandatory for weldable 13Cr line pipes, but the developed material welded joints without PWHT show sufficient SCC resistance at elevated temperature as well as the SSC resistance at an intermediate temperature, 900C. The most susceptible temperature for cracking is also investigated in this study. The purposes of this research are to assess the SSC resistance at as-welded conditions in slightly sour environment and evaluate the stress corrosion cracking (SCC) susceptibility at intermediate and elevated temperature. In addition, the hydrogen induced stress cracking susceptibility of the developed material was also investigated.

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