时效处理对S32750超级双相不锈钢在低温海水中腐蚀行为的影响
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摘要
不恰当的焊接或热处理会导致S32750超级双相不锈钢(SDSS)产生析出物,从而影响S32750 SDSS的腐蚀行为。通过金相显微镜观察了S32750 SDSS经850℃时效处理10,60,120 min后的显微组织,采用X射线衍射仪分析了时效处理后各试样的物相结构,并借助极化曲线、电化学阻抗谱和Mott-Schottky曲线等方法,研究了不同时间时效处理对S32750 SDSS在低温模拟海水(5℃的3.5%NaCl溶液)中腐蚀行为的影响,使用金相显微镜观察其极化曲线测试后的表面形貌。结果表明:当时效时间为10 min时,S32750 SDSS内有σ相析出;随着时效时间的延长,σ相的析出量逐渐增多,S32750 SDSS在低温海水中的自腐蚀电流密度和维钝电流密度也随之增大,击穿电位随之下降,蚀坑数量逐渐增多,腐蚀逐渐变得严重,抗腐蚀性能随之下降,这主要与σ相降低了钝化膜的稳定性、增加了腐蚀原电池的数量等有关。
The corrosion behavior of S32750 super duplex stainless steel( SDSS) was affected by the precipitate phase caused by the unsuitable welding or improper heat treatment. The microstructure of S32750 SDSS after aging treatment at 850 ℃ for 10,60,120 min was observed by metallurgical microscope,and the phases in the heat-treated SDSS samples were characterized by X-ray diffractometer( XRD). In addition,the influences of aging treatment with different temperature on the corrosion resistance of samples in 3.5% Na Cl solution at low temperature( 5℃) were evaluated by potentiodynamic polarization,electrochemical impedance spectra( EIS) and Mott-Schokkty plots,and the morphology after polarization was observed by metallurgical microscope( OM). Results showed that the σ-phase was precipitated when S32750 SDSS was aged for 10 min at 850 ℃,and the content of σ-phase increased with increasing aging time. As the aging time prolonged,the free corrosion current density and passive current density also increased,and meantime the pitting potential decreased and the number of pitting increased,which indicated the corrosion become more serious and the corrosion resistance declined. This phenomenon mainly resulted from the reduction of the stability of the passive film and the increase of the number of corrosion cells by the σ-phase precipitate and so on.
The corrosion behavior of S32750 super duplex stainless steel( SDSS) was affected by the precipitate phase caused by the unsuitable welding or improper heat treatment. The microstructure of S32750 SDSS after aging treatment at 850 ℃ for 10,60,120 min was observed by metallurgical microscope,and the phases in the heat-treated SDSS samples were characterized by X-ray diffractometer( XRD). In addition,the influences of aging treatment with different temperature on the corrosion resistance of samples in 3.5% Na Cl solution at low temperature( 5℃) were evaluated by potentiodynamic polarization,electrochemical impedance spectra( EIS) and Mott-Schokkty plots,and the morphology after polarization was observed by metallurgical microscope( OM). Results showed that the σ-phase was precipitated when S32750 SDSS was aged for 10 min at 850 ℃,and the content of σ-phase increased with increasing aging time. As the aging time prolonged,the free corrosion current density and passive current density also increased,and meantime the pitting potential decreased and the number of pitting increased,which indicated the corrosion become more serious and the corrosion resistance declined. This phenomenon mainly resulted from the reduction of the stability of the passive film and the increase of the number of corrosion cells by the σ-phase precipitate and so on.
引文
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[15]向红亮,何福善,刘东.超级双相不锈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(4):288-294.
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[19] CHENG Y F,LUO J L. A comparion of the pitting susceptibility and semiconducting properties of the passive films on carbon steel in chromate and bicarbonate solutions[J]. Applied Surface Science,2000,167(1):113-121.
[20]魏欣,董俊华,佟健,等.温度对Cr26Mo1超纯高铬铁素体不锈钢在3.5%NaCl溶液中耐点蚀性能的影响[J].金属学报,2012,48(5):502-507.
[2]刘智勇,万红霞,李禅,等. X65管线钢焊接接头在模拟浅表海水和深海环境中的腐蚀行为对比[J].中国腐蚀与防护学报,2014,34(4):321-326.
[3] SHAN L,ZHANG Y R,WANG Y X,et al. Corrosion and wear behaviors of PVD Cr N and Cr Si N coatings in seawater[J]. Transactions of Nonferrous Metals Society of China,2016,26(1):175-184.
[4]聂薇,姚晓红,卢本才.海洋工程重防腐技术[J].造船技术,2016(6):82-86.
[5] YANG Y,YAN B,YIN J,et al. Microstructure and corrosion behaviour aging at 750℃in 25%Cr duplex stainless steel[J]. Rare Metals,2011,30(1):515-519.
[6] BHATTACHARYA A,SINGH P M. Effect of heat treatment on corrosion and stress corrosion cracking of S32205 duplex stainless steel in caustic solution[J]. Metallurgical&Materials Transcations A,2009,40(6):1 388-1 399.
[7]韩冬,蒋益明,邓博,等.时效时间对2101双相不锈钢电化学腐蚀行为的影响[J].金属学报,2009,45(8):919-923.
[8]李俊.固溶处理对超级双相不锈钢S32750组织和性能的影响[J].特殊钢,2012,33(4):64-66.
[9]王佳,孟洁,唐晓,等.深海环境钢材腐蚀行为评价技术[J].中国腐蚀与防护技术,2007,27(1):1-7.
[10] ATAPOUR M,SARLAK H,ESMAILZADEH M. Pitting corrosion susceptibility of friction stir welded lean duplex stainless joints[J]. The International Journal of Advanced Manufacturing Technology,2016,83(5-8):721-728.
[11]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(12):1 456-1 460.
[12]逄旭光,梁平,张云霞,等. 2205和316L不锈钢在氢氟酸中的电化学腐蚀行为[J].腐蚀科学与防护技术,2016,28(6):537-542.
[13] LUO H,DONG C F,CHENG X Q,et al.Electrochemical behavior of 2205 duplex stainless steel in Na Cl solution with different chromate contents[J]. Journal of Materials Engineering&Performance,2012,21(7):1 283-1 291.
[14] GERVASI C A,FOLQUER M E,VALLEJO A E,et al.Electron transfer across anodic films formed on tin in carbonate-bicarbonate buffer solution[J]. Electrochimica Acta,2005,50(5):1 113-1 119.
[15]向红亮,何福善,刘东.超级双相不锈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(4):288-294.
[16] FENG Z,CHENG X,DONG C,et al. Passivity of 316L stainless steel in borate buffer solution studied by MottSchottky analysis,atomic absorption spectrometry and X-ray photoelectron spectroscopy[J]. Corrosion Science,2010,52(11):3 646-3 653.
[17] KRISHNAMURTHY B,WHITE R E,PLOEHN H J. Simplified point defect model for growth of anodic passive films on iron[J]. Electrochimica Acta,2003,47(20):3 375-3 381.
[18] AMRI J,SOUIER T,MALKI B,et al. Effect of the final annealing of cold rooled stainless steels sheets on the electronic properties and pit nucleation resistance of passive films[J]. Corrosion Science,2008,50(2):431-435.
[19] CHENG Y F,LUO J L. A comparion of the pitting susceptibility and semiconducting properties of the passive films on carbon steel in chromate and bicarbonate solutions[J]. Applied Surface Science,2000,167(1):113-121.
[20]魏欣,董俊华,佟健,等.温度对Cr26Mo1超纯高铬铁素体不锈钢在3.5%NaCl溶液中耐点蚀性能的影响[J].金属学报,2012,48(5):502-507.