51314-4439-The Influence of the Heat Input on the Secondary Phases Transformations and the Impact on the Corrosion Resistance of a Super Duplex GMAW-P Welding

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Product Number: 51314-4439-SG

ISBN: 4439 2014 CP

Author: Thiago Chehuan

Publication Date: 2014

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Due to the combination of good mechanical properties and superior corrosion resistance when compared to other stainless steels the duplex stainless steel is an important material for the oil & gas industry especially off-shore in high pressure and highly corrosive systems. However the existence of some secondary phases that precipitates during the welding process are routinely found in production joints and might present risks on the use of these materials.The current work focus on the effect of secondary phase mainly secondary austenite on corrosion resistance of welded joints. The weld joints were obtained by pulsed MIG (GMAW-P) with three different heat inputs. Each joint and their respectively sub-regions were characterized by optical microscopy SEM EBSD and that results correlated with electrochemical and SSC tests.Results suggest an explicit relation between the DL-EPR electrochemical testing results and the four point bending SSC testing. It was also verified that the simple existence of secondary austenite does not necessarily imply on loss of corrosion resistance its effect seems to be related to the region where it was precipitated morphology distribution size and possibly chemical composition. Finally the use of an adequate welding procedure proved to be an efficient tool on preventing loss of corrosion resistance and the DL-EPR a promissory technique for welding procedures qualification and/or production testing.