时效温度对S32750超级双相不锈钢组织和抗氢氟酸腐蚀性能的影响
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摘要
通过金相显微镜和扫描电镜观察了S32750超级双相不锈钢(SDSS)经650~1000℃时效处理后的显微组织和微观形貌;通过XRD分析了时效后各试样的物相结构;借助动电位极化、电化学阻抗和Mott-Schokkty曲线等方法,考察了时效后的S32750 SDSS在5%(体积分数)HF溶液中的腐蚀行为。结果表明:当时效温度为650和1000℃时,S32750 SDSS内并没有析出物产生。当温度上升到750~950℃时,开始产生σ析出相;且温度为850℃时,σ析出相最多,抗氢氟酸腐蚀性能最差。这主要是因为析出的σ相造成了材料内Cr和Mo分布的不均匀,促进了腐蚀微电池的形成,加快了不锈钢的溶解。同时,σ相的析出也增大了钝化膜的载流子密度,促进了F-的吸附,增大了钝化膜的溶解速率,降低了钝化膜的稳定性,加快了双相不锈钢的腐蚀。
S32750 super duplex stainless steel(SDSS) was aged in the temperature range 650 ℃to 1000 ℃,and then was characterized by means of optical microscope(OM),scanning electronic microscope(SEM) and X-ray diffractometer(XRD).The corrosion resistance of the aged steel in 5%(volume fraction) HF solution was assessed by measurements of potentiodynamic polarization,electrochemical impedance spectra(EIS) and Mott-Schokkty plots.Results show that the σ phase precipitated in the steel in the temperature range from 750 ℃ to 950 ℃,but not at 650 ℃ and 1000 ℃ respectively.Among others,the amount of σ phase is the highest and correspondingly,the corrosion resistance is also the worst for the steel aged at 850 ℃.This is mainly because of that the precipitates of σ phase lead to the segregation of Cr and Mo within the steel,thus the non-uniform distribution of the alloying elements in the steel may induce galvanic corrosion within the steel,which accelerates the dissolution of SDSS.At the same time,the σ phase precipitation may also induce the increase of carrier densities of the formed passive film of the steel in HF solution,which enhanced the adsorption of F-,and in turn the dissolution rate of passive film and finally reduced the stability of the passive film,thus,the corrosion rate of SDSS in HF is accelerated.
S32750 super duplex stainless steel(SDSS) was aged in the temperature range 650 ℃to 1000 ℃,and then was characterized by means of optical microscope(OM),scanning electronic microscope(SEM) and X-ray diffractometer(XRD).The corrosion resistance of the aged steel in 5%(volume fraction) HF solution was assessed by measurements of potentiodynamic polarization,electrochemical impedance spectra(EIS) and Mott-Schokkty plots.Results show that the σ phase precipitated in the steel in the temperature range from 750 ℃ to 950 ℃,but not at 650 ℃ and 1000 ℃ respectively.Among others,the amount of σ phase is the highest and correspondingly,the corrosion resistance is also the worst for the steel aged at 850 ℃.This is mainly because of that the precipitates of σ phase lead to the segregation of Cr and Mo within the steel,thus the non-uniform distribution of the alloying elements in the steel may induce galvanic corrosion within the steel,which accelerates the dissolution of SDSS.At the same time,the σ phase precipitation may also induce the increase of carrier densities of the formed passive film of the steel in HF solution,which enhanced the adsorption of F-,and in turn the dissolution rate of passive film and finally reduced the stability of the passive film,thus,the corrosion rate of SDSS in HF is accelerated.
引文
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[3]Theodoro M C,Pereira V F,Mei P R,et al.Dissimilar friction stir welding between UNS S31603 austenitic stainless steel and UNS S32750 super duplex stainless steel[J].Metall.Mater.Trans.,2015,46B:1440
[4]Shamanian M,Mohammadnezhad M,Amini M,et al.Electron backscatter diffraction analysis of joints between AISI 316L Austenitic/UNS S32750 dual-phase stainless steel[J].J.Mater.Eng.Perform.,2015,24:3118
[5]Berecz T,Fazakasé,Mészáros I,et al.Decomposition kinetics of ferrite in isothermally aged SAF 2507-type duplex stainless steel[J].J.Mater.Eng.Perform.,2015,24:4777
[6]Zhao Z Y,Xu L,Li G P,et al.Precipitation behavior ofσ-phase and its effect on microstructure and properties of a super duplex stainless steel[J].Trans.Mater.Heat Treat.,2010,31(10):75(赵志毅,徐林,李国平等.超级双相不锈钢σ相析出及对组织性能的影响[J].材料热处理学报,2010,31(10):75)
[7]Xiang H L,He F S,Liu D.Effects of aging temperature on precipitation phase of a cast super duplex stainless steel[J].Acta Metall.Sin.,2009,45:1456(向红亮,何福善,刘东.时效温度对铸造超级双相不锈钢析出相的影响[J].金属学报,2009,45:1456)
[8]Zou D N,Han Y,Zhang W,et al.Sigma phase precipitation and properties of super-duplex stainless steel UNS S32750 aged at the nose temperature[J].J.Wuhan Univ.Technol.Mater.Sci.,2011,26:182
[9]Guo L F,Li X J,Sun T,et al.The influence of sensitive temperature on the localized corrosion resistance of duplex stainless steel SAF2304[J].Acta Metall.Sin.,2012,48:1503(郭丽芳,李旭姜,孙涛等.敏化温度对SAF2304双相不锈钢耐局部腐蚀性能的影响[J].金属学报,2012,48:1503)
[10]Rahmani M,Eghlimi A,Shamanian M.Evaluation of microstructure and mechanical properties in dissimilar austenitic/super duplex stainless steel joint[J].J.Mater.Eng.Perform.,2014,23:3745
[11]Bhattacharya A,Singh P M.Effect of heat treatment on corrosion and stress corrosion cracking of S32205 duplex stainless steel in caustic solution[J].Metall.Mater.Trans.,2009,40A:1388
[12]Cheng X Q,Li X G,Du C W.Properties of passive film formed on316L/2205 stainless steel by Mott-Schottky theory and constant current polarization method[J].Chin.Sci.Bull.,2009,54:2239
[13]Ferreira M G S,Hakiki N E,Goodlet G,et al.Influence of the temperature of film formation on the electronic structure of oxide films formed on 304 stainless steel[J].Electrochim.Acta,2001,46:3767
[14]Xiang H L,He F S,Liu D.Corrosion compositions on surface after electrochemical polarization of duplex stainless cast steel by XPS[J].J.Chin.Soc.Corros.Prot.,2010,30:288(向红亮,何福善,刘东.超级双相不锈铸钢电化学极化表面腐蚀产物的XPS分析[J].中国腐蚀与防护学报,2010,30:288)
[15]Ye W,Li Y,Wang F H.Effect of nanocrystallization on the electrochemical corrosion behavior of 309 stainless steel[J].J.Chin.Soc.Corros.Prot.,2008,28:25(叶威,李瑛,王福会.309不锈钢纳米涂层在酸性溶液中的电化学腐蚀行为[J].中国腐蚀与防护学报,2008,28:25)
[16]Dong Y,Lin X P,Jiang X X.Effect of Cr,Mo on resistance to the corrosion and corrosion wear of stainless steel[J].Mater.Mech.Eng.,1997,21:29(董允,林晓娉,姜晓霞.铬、钼对不锈钢腐蚀与腐蚀磨损性能的影响[J].机械工程材料,1997,21:29)
[17]Ye W,Li Y,Wang F H.Electrochemical corrosion behavior of nano-crystalline stainless steel coating with different phase composition[J].J.Chin.Soc.Corros.Prot.,2008,28:129(叶威,李瑛,王福会.单相和双相不锈钢纳米涂层的电化学腐蚀行为[J].中国腐蚀与防护学报,2008,28:129)
[18]Mac Donald D D,Urquidi-Mac Donald M.Theory of steady state passive films[J].J.Electrochem.Soc.,1990,137:2395
[19]Mac Donald D D.The point defect model for the passive state[J].J.Electrochem.Soc.,1992,139:3434
[20]Cheng X Q,Li C T,Li X G,et al.Constituent phases of the passive film formed on 2205 stainless steel by dynamic electrochemical impedance spectroscopy[J].Int.J.Miner.Metall.Mater.,2011,18:42