51314-3967-High Nitrogen Super-Austenitic Stainless Steel for Heavy Thickness Components in Oil and Gas

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Product Number: 51314-3967-SG

ISBN: 3967 2014 CP

Author: JEAN-MARC LARDON

Publication Date: 2014

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Super-austenitic stainless steels commercially available today present a high corrosion resistance in oil and gas environments though their resistance to stress corrosion cracking (SCC) but do not reach those of Nickel base alloys (625 alloy 276 or alloy 22). These good properties are however limited to components of small thickness due to the propensity of these steels to form intermetallic compounds (sigma or chi phase) or chromium nitrides during water cooling after annealing.Heavy weight and/or very thick nickel based alloy components are also difficult to manufacture due to high level of segregation in large re-melted ingots which still remains in the final product and can impair the corrosion resistance. Furthermore nickel base alloys are expensive have relatively low mechanical properties in the annealed condition or can sometimes be susceptible to hydrogen embrittlement for annealed and aged alloys .NYB66W super-austenitic stainless steel has been developed to cope with these drawbacks of commercially available corrosion resistant alloys (CRA). UNS 31266 super-austenitic stainless steel shows equivalent mechanical properties as 625 Grade1 alloy with improved microstructural stability allowing the manufacture of heavy and high thickness components. Ductility and toughness down to cryogenic temperatures are also far greater than those of super-duplex stainless steels and behavior of NYB66W in sour gas environments outperforms those of conventional super-duplex or super-austenitic stainless steels.This paper reviews the properties of NYB66W super-austenitic stainless steel for use in different environments which can be encountered in the Oil and Gas industry. A specific focus is also made on the possibility to use Powder Metallurgy for complex shapes and heavy weight components.