51312-01746-Effect of Cold Work on Stress Corrosion Cracking Susceptibility of Duplex Stainless Steels in Hot Al

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Product Number: 51312-01746-SG

ISBN: 01746 2012 CP

Author: Pekka Pohjanne

Publication Date: 2012

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The effect of 20% cold work on SCC susceptibility of the duplex stainless steels EN1.4162 (UNS S32101) and EN1.4462 (UNS S32205) was evaluated with U-bend specimens in the alkaline sulfide solution containing 100 g/l NaOH and 55 g/l Na2S at 190ºC. Complementary corrosion potential measurements were used to evaluate the effect of cold work on corrosion and on passivation behavior of the duplex stainless steels. The reference material in the study was the austenitic stainless steel EN1.4301 (AISI 304). Residual stress state in the duplex grades was evaluated in annealed and 20% cold worked samples using X-ray diffraction. The effect of cold work on SCC susceptibility of the duplex stainless steels could be connected to the plastic zone at the crack tip which decreased with increasing cold work. Observed cracking in the cold worked duplex stainless steels was more severe in EN1.4162 than in EN1.4462. Residual stress state was shown to influence the crack distribution and morphology particularly away from the highest stressed region at the apex of the specimens.Based on separate potentiodynamic curves and the free corrosion potential measurements of the alloys during the SCC tests it is evident that Cr and Ni as the main alloying elements in duplex stainless steels raised the corrosion potential and lowered critical current density of the steel thus improved SCC resistance. The role of Mn alloying of the duplex stainless steels in SCC susceptibility remains unclear because of the heavy general corrosion in the studied environment.