Duplex and super duplex stainless steels state of the art and future developments

摘要

Duplex stainless steels containing over 20% chromium with molybdenum and nitrogen additions have been around for many years. The 22 Cr type (UNS S31803) have limitations in high chloride environments, such as sea water. 25 Cr duplex, and particularly super duplex, alloys have improved corrosion resistance and are finding extensive use in the marine environment. This paper describes the current areas where duplex and super duplex alloys are being used by the oil and gas industry. The diversity of components which have been supplied in 25 Cr super duplex stainless steel is covered as is the range of environmental conditions for both sea water and produced/injection waters which are being successfully handled. The corrosion problems being overcome include pitting/crevice corrosion, stress corrosion cracking and erosion corrosion.rnAlso described are the environmental conditions in some new or under developed market areas where the combination of high strength and good corrosion resistance of super duplex stainless steel offers the possibilities of long service life at low cost compared to alternative materials.