51314-3783-Effect of Cold Work on the Stress Corrosion Cracking Behavior of 316L Stainless Steel in Sour Service

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Product Number: 51314-3783-SG

ISBN: 3783 2014 CP

Author: David Fischer

Publication Date: 2014

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Type 316L (UNS S31603) austenitic stainless steel (SS) is widely utilized in topside facilities for oil and gas production due to its good weldability high availability capability of being clad and relatively low cost compared to other corrosion resistant alloys. For certain components cold working of the material may be desired to enhance mechanical properties (e.g. strength hardness) or in other cases be imparted into the material through shaping or forming operations. Cold working of 316L SS however is not permitted for sour service applications as it is generally known to increase the susceptibility of this material to stress corrosion cracking (SCC). As a result any component in sour service being used in a cold-worked condition must be upgraded to a more expensive material design.In the present work a systematic laboratory study was done to more accurately assess the effects of cold work (CW) on the SCC behavior 316L SS under various combinations of hydrogen sulfide partial pressure (PH2S) temperature (T) and chloride concentrations ([Cl-]). Sheets of annealed 316L SS were cold rolled to 5% and 10% reductions in cross-sectional area resulting in an increase in maximum hardness from 176 HV (annealed) to 227 HV (5% CW) and 256 HV (10% CW). Four-point bend (FPB) tests were conducted on the annealed and cold-worked 316L SS materials to 100% actual yield strength (AYS) under the following ranges of environmental conditions: PH2S = 0.01-10 bar T = 40-100 °C [Cl-] = 1000-120000 ppm. Cross-sectional metallographic analysis was performed post-test to identify the presence of pitting or SCC and in the case the latter the mode of fracture. Through this investigation the knockdown in 316L SS sour service limits due to cold-work was evaluated.Keywords: SCC pitting cold work chloride austenitic stainless steel metallography