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.
出处
《中国腐蚀与防护学报》
CAS
CSCD
北大核心
2017年第6期519-525,共7页
Journal of Chinese Society For Corrosion and Protection
基金
国家自然科学基金(51175240)
辽宁省教育厅2012年科学研究一般项目(L2012127)~~
关键词
S32750超级双相不锈钢
氢氟酸
Σ相
时效温度
S32750 super duplex stainless steel, hydrofluoric acid, σ phase, aging temperature
