51316-7618-Pitting and H2S Corrosion Resistance of the New Formable Duplex Grades

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Product Number: 51316-7618-SG

ISBN: 7618 2016 CP

Author: Mikael Schönning

Publication Date: 2016

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UNS S82012 and UNS S82031 are two newly developed duplex stainless steels that have recently been incorporated into the ASTM A240 standard. These new innovative materials utilize the Transformation Induced Plasticity (TRIP) effect and show significantly improved formability properties compared to other duplex grades. The chemical composition of UNS S82012 and UNS S82031 is balanced to give optimal austenite stability yielding a controlled transformation of austenite to martensite during cold forming operations. The excellent combination of high mechanical strength and good formability of these new duplex grades opens up for demanding cold forming applications that were previously reserved for standard austenitic grades such as UNS S30403 and UNS S31600.In an earlier study carried out on specimens with carefully controlled deformation the new formable duplex steels UNS S82012 and UNS S82031 showed no significant impact of deformation and martensite on the pitting corrosion resistance. However industrial surface treatment techniques such as grinding and abrasive blasting may induce much different surface conditions than previously investigated. In this study the formable duplex steels were evaluated with different surface conditions: shot peened dry ground and wet ground. Standard austenitic grades were also included in the study as reference. A metallographic study was conducted to evaluate the surface condition caused by the different surface treatments. The metallographic findings were correlated to the pitting corrosion test results. In addition sour testing results of UNS S82031 in both annealed and deformed condition are discussed.Key words: duplex stainless steel deformation TRIP critical pitting temperature sour service testing H2S