Effect of aging on the corrosion resistance of 2101lean duplex stainless steel
Lihua Zhang a ,Yiming Jiang a ,Bo Deng a ,Wei Zhang b ,Juliang Xu a ,Jin Li a,⁎
a Department of Material Science,Fudan University,Shanghai 200433,PR China b
Institute of stainless steel,Baosteel Co.,Ltd,Shanghai 200431,PR China
A R T I C L E D A T A
A B S T R A C T
Article history:Received 7May 2009Received in revised form 14August 2009
Accepted 29August 2009The microstructure and localized corrosion behavior of a 2101lean duplex stainless steel aged at 700°C were investigated.The results showed that changes in the microstructure of the duplex stainless steel,due to the formation of precipitates,affected its pitting corrosion resistance.The values of the pitting potential and the critical pitting temperature dropped drastically before aging time up to 30min.The potentiostatic pitting corrosion measurement indicated more sensitive to the small amount of precipitates compared to the potentiodynamic test.Pitting nucleated mainly in the ferrite phase for the solution-annealed specimen,while the initiation of pitting corrosion for the aged specimen took place at Cr-depletion area around the precipitates,i.e.in the newly formed secondary austenite phase.
©2009Elsevier Inc.All rights reserved.
Keywords:
Duplex stainless steel Aging Precipitation Pitting corrosion
1.Introduction
Duplex stainless steels (DSS)are being increasingly employed in chemical,petrochemicals,nuclear,and marine industries primarily due to their excellent mechanical property in combination with good corrosion performance [1].It is well established that DSS exhibit optimum properties when their ferrite to austenite (α/γ)volume ratios are about 1:1[2]and no other tertiary phases are present.However,during fabrication,such as welding and other thermal treatments,the ferrite to austenite volume ratios may be changed along with the precipitation of various compounds (e.g.chromium carbides and nitrides)and some other intermetallic phases (like sigma (σ),chi (χ),secondary austenite (γ2))[3–5].These microstruc-tural modifications have a detrimental effect on mechanical and corrosion resistance properties of the DSS.A significant amount of work,that studied the effect of heat treatment and
precipitation on the corrosion behavior of commonly used DSS grades such as 2205(UNS S32205),2304(UNS S32304),and 2507(UNS S32507),had been published [6–9].
Since 2000,with the high fluctuation of the nickel price,DSS 2101(EN 1.4162,UNS S32101)containing less than 2%nickel has made it attractive.The reduced nickel content is compensated by an increase in the amount of manganese and nitrogen in the steel to stabilize the austenite phase in duplex microstructures [10].The molybdenum content of this steel is also significantly reduced to limit the precipitation of delete-rious phases.Liljas [11]in the review article on DSS 2101explored the utility of this new duplex family in a wide variety of applications,replacing austenitic steels of type 304and also,to some extent,structural steels.Westin [12]addressed the effect of alloying elements and thermal cycles on phase balance and microstructure in the high temperature heat-affected zone (HTHAZ)of DSS 2101.The authors [13]also
M A T E R I A L S C H A R A C T E R I Z A T I O N 60(2009)1522–1528
⁎Corresponding author.Tel.:+862165643648;fax:+862165643648.E-mail address:jinli@ (J.
Li).
1044-5803/$–see front matter ©2009Elsevier Inc.All rights reserved.doi:
10.1016/j.matchar.2009.08.009
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