HR3C在超临界水中的腐蚀性能研究

通过高压釜浸泡实验研究了超级奥氏体不锈钢HR3C在循环的超临界水（SCW）中的均匀腐蚀性能,实验温度分别为550、600、650 ℃,压力为25 MPa,并对实验后试样生成的氧化膜进行了SEM、EDS和XRD分析。实验结果显示,HR3C在SCW环境中的氧化腐蚀速率随着温度的升高而增大,1 500 h后650 ℃ SCW环境下材料的腐蚀增重约为550 ℃时的2倍。材料表面生成的氧化膜主要成分为FeCr₂O₃、Fe₃O₄和Fe₂O₃,内层氧化膜富Cr而外层氧化膜富Fe。     

含铝奥氏体耐热钢在超临界二氧化碳中的腐蚀行为

研究了20Cr-25Ni合金和一种新型结构材料含铝的奥氏体耐热钢(AFA钢)在600℃/20 MPa的超临界二氧化碳(S-CO₂)环境中的腐蚀行为,并对2种合金的氧化膜形貌、成分和结构进行分析。研究发现,20Cr-25Ni合金出现明显的腐蚀增重增长趋势,表现出“抛物线”上升规律;AFA钢腐蚀增重趋势缓慢,腐蚀1000 h后仅为2.11 mg/dm²。20Cr-25Ni合金表面出现粗大的氧化产物,随腐蚀时间延长,AFA钢的氧化膜始终保持致密、连续。通过氧化膜的截面形貌分析发现,20Cr-25Ni合金腐蚀后具有两层氧化膜结构,主要由Fe₃O₄和FeCr₂O4_氧化层以及少量尖晶石组成。而AFA钢中出现了3层氧化膜结构,中间和最内层分别为Cr₂O₃和Al₂O₃氧化膜,最外层分布了一层不连续的FeCr₂O₄尖晶石氧化物。由于形成了致密的...     

AP1000一回路氧化膜特性研究

AP1000与一般压水堆不同的是其一回路采用注锌加氢技术,使其一回路氧化膜特性发生变化。试验在高压釜中模拟AP1000一回路水化学工况,研究F304L、F316、690三种反应堆主工艺设备材料表面生成的氧化膜特性。结果表明,氧化膜为双层结构,外层氧化膜成分主要是Fe₂O₃及Fe₃O₄。F304L不锈钢与F316不锈钢内层氧化膜主要是ZnCr₂O₄,注入的Zn元素取代了FeCr₂O₄中的铁元素,形成了致密的ZnCr₂O₄ 氧化层,内层氧化膜存在少量ZnO和ZnFe₂O₄。690合金的氧化膜内层为ZnCr₂O₄,同时存在较高含量的ZnO和ZnFe₂O₄。与前两者不同的是,690合金的氧化膜含少量的二价镍,以NiFe₂O₄和NiCr₂O₄形式存在。加锌加氢使得氧化膜更加致密,也明显变薄。     

MA956在超临界水环境中的腐蚀性能

研究MA956在550/600/650℃超临界水(SCW)中的腐蚀特性,采用扫描电镜(SEM)、X射线能谱仪(EDS)和X射线衍射仪(XRD)分析氧化膜的表面形貌、组织结构和元素分布。由MA956的腐蚀增重曲线可知,其在SCW中腐蚀1000 h后其重量基本不变,具有优良的抗腐蚀性能。MA956在SCW中形成的氧化膜分层不明显,为单层结构,氧化膜中富Al、贫Fe。当温度大于或等于600℃时,腐蚀1000 h试样表面分布着大量的Al2O3白色颗粒物,在650℃时白色颗粒物的平均尺寸达8μm。经预氧化的MA956抗腐蚀性能进一步提高,1000 h后在其表面依然光滑平整,并未出现点蚀坑。     

候选材料在650 ℃超临界水中的腐蚀行为研究

研究了3种候选材料（347、HR3C和In-718）在650 ℃、25 MPa去离子水中的均匀腐蚀行为,使用场发射扫描电镜（FEG-SEM）和能谱（EDS）观察了不同腐蚀时间的表面氧化膜形貌与合金元素分布,使用掠入射X射线衍射（GIXRD）分析了氧化膜相结构。结果表明,3种材料腐蚀失重均符合抛物线规律,347的失重为HR3C和In 718的40倍以上;3种材料氧化膜均以Ni(Cr, Fe) ₂O₄为主,In-718点蚀严重,347氧化膜明显脱落,HR3C氧化膜较均匀致密;高温超临界水中,提高合金的Cr含量有助于增强均匀腐蚀性能,添加Nb有损合金的点蚀抗力。     

超临界二氧化碳环境中600合金和304不锈钢的均匀腐蚀行为研究

为遴选可用于超临界二氧化碳核反应堆的结构材料,通过实验研究了应用于传统核反应堆中的两种合金（600合金和304不锈钢）在650℃、20 MPa的超临界二氧化碳环境中的均匀腐蚀行为,运用增重法评价了材料的腐蚀动力学规律,采用扫描电镜、能谱仪和Ｘ射线衍射仪分析了氧化膜形貌、结构和化学成分。结果表明,两种材料的腐蚀增重均服从抛物线生长规律,其中600合金的耐腐蚀性能优于304不锈钢;腐蚀500 h后,600合金表面氧化物厚度约为5 μm,主要成分为NiCr₂O₄,结构致密,具有保护性,其氧化膜及基体中均未发现明显渗碳行为;腐蚀500 h后,304不锈钢表面氧化膜可达约45 μm,为双层结构,外层为Fe₃O₄,内层为NiFeCrO₄,结构疏松,发生显著渗碳现象。本研究揭示了上述材料在超临界二氧化碳中的腐蚀机理,为超临界二氧化碳核反应堆结构材料的选择提供了数据支持。      

316NG不锈钢在硼-锂溶液中的电化学腐蚀行为研究

利用电化学方法获得316NG不锈钢（316NG）在300℃、pH=5~8硼-锂溶液中的极化曲线和交流阻抗（EIS）,并绘制相应水化学条件下的电位-pH图。结果表明:碱性条件下钝化区尤其是二次钝化区极化电流急剧减小,pH=7~8时阳极极化表现出3次钝化现象,偏碱性条件极化阻抗显著高于偏酸性和近中性条件,说明碱性条件下316NG表面钝化膜保护效果更佳。pH=5时电化学极化后样品表面主要生成Cr₂O₃和Fe₂O₃;碱性条件下（pH=6~8）样品表面氧化膜为分层结构:最外层为Fe₃O₄,随深度增加开始出现NiFe₂O₄,内层成分主要为FeCr₂O₄。随着电导率升高,溶液电阻、电荷传递电阻和钝化膜电阻均显著降低。依据极化曲线绘制的电位-pH图与文献结果相吻合。      

F/M钢在超临界水环境中的腐蚀性能

本文研究了F/M钢在超临界水（SCW）环境中的腐蚀性能。实验结果表明,F/M钢在SCW中的抗腐蚀性能较差,温度、溶氧浓度以及材料中的Cr含量对其腐蚀性能有较大影响。对12Cr表面进行盐浴复合处理（QPQ）、电镀Cr和磁控溅射Cr处理,以研究其对F/M钢在SCW中抗腐蚀性能的影响。研究表明,经电镀Cr和磁控溅射Cr处理的12Cr试样在SCW中具有优良的抗腐蚀性能,尤其是经磁控溅射Cr处理的试样,1 000 h后其表面氧化膜依然完整致密,而经QPQ的试样腐蚀严重。     

不锈钢及高温合金在拟临界区的腐蚀行为研究

研究3种高温合金和4种奥氏体不锈钢在380℃、25 MPa去离子水中的均匀腐蚀行为,使用场发射扫描电镜(FEG-SEM)和X射线能谱仪(EDS)分析不同腐蚀时间的表面氧化膜形貌与合金元素分布。结果表明,实验工况下合金腐蚀增重无明显规律,腐蚀失重均为对数规律;HR3C合金腐蚀失重最小,347合金最大,二者相差一个数量级。所有材料表面均能生成较为完整致密的双层氧化膜,外层相对贫Cr、Ni,缺Mo而富O。316Ti、718、825、800H、HR3C等多种合金出现点蚀,依照成分不同,点蚀区域呈现富Nb、Ti,贫Cr、Ni,缺Mn、Mo等现象。     

奥氏体304NG不锈钢在550℃/25MPa超临界水中的腐蚀行为

研究了304NG不锈钢在550℃/25MPa超临界水中的腐蚀特性。采用扫描电镜、X射线能谱仪和X射线衍射分析了氧化膜的腐蚀形貌、组织结构和元素成分分布。实验结果表明,在550℃/25MPa的超临界水中腐蚀1000h后,304NG不锈钢显示出优越的耐腐蚀性能,其均匀腐蚀增重速率仅为0.01299mg•dm^-2•h^-1。304NG不锈钢在超临界水中形成均匀致密、但带有疖状腐蚀的双层氧化膜,厚度约为2.0μm,内层氧化膜致密而富Cr和Ni,外层氧化膜疏松而富Fe。     

304NG在超临界水中腐蚀后氧化膜分析

研究了奥氏体不锈钢304NG(以下简称304NG)在压力为25 MPa,温度分别为500、550、600、650℃超临界水中的腐蚀行为,通过扫描电镜-电子能谱(SEM-EDX)、X射线衍射(XRD)对304NG试样氧化膜微观组织的研究表明:304NG在超临界水中腐蚀后,表面氧化膜由岛状和非岛状2种不同形貌的腐蚀相组成.其中,含岛状腐蚀相的氧化膜具有双层结构,外层为Fe3O4相,内层为Fe3O4和FeCr2O4相;不含岛状腐蚀相的氧化膜为单层结构,氧化膜中含有Fe3O4和FeCr2O4相.同时,304NG在超临界水中氧化膜存在脱落现象,氧化膜脱落程度随温度升高而加剧.     

铁素体-马氏体钢P92在超临界水中的腐蚀性能

研究了P92钢在550和600℃超临界水中的腐蚀特性,采用扫描电镜、X射线能谱仪和X射线衍射仪分析了氧化膜的表面形貌、组织结构和元素分布。结果表明：P92钢在超临界水中的氧化动力学大致服从立方生长规律,600℃下P92钢的腐蚀增重和氧化膜厚度均为550℃时的3倍。P92钢在超临界水中形成的氧化膜为双层结构,氧化膜外层富Fe,而内层富Cr。600℃时P92钢氧化膜发生了开裂和剥落,其原因主要在于降温过程中基体与氧化物间的热膨胀系数不相匹配而产生的较大热应力。     

T91钢在氧浓度为0.01ppm静态铅铋合金中的界面腐蚀特征

开展了铅基反应堆候选结构材料T91钢在500℃、0.01ppm氧浓度、静态铅铋共晶合金(LBE)中的腐蚀行为研究,腐蚀时间依次为500、1 000、2 000h。采用SEM观察腐蚀界面组织形貌,并结合EDX分析界面产物成分及元素扩散行为。结果显示:T91钢发生了氧化腐蚀,表面生成了具有3层结构的氧化膜。最外层为疏松且有LBE渗透的Fe3O4层,中间层为致密且具有保护性的(Fe,Cr)3O4层,最内层为富含铬元素的内氧化层(IOZ)。随着腐蚀时间的增加,Fe3O4层和(Fe,Cr)3O4层的厚度先快速增加,在1 000h时分别达到6.5μm和7.4μm;随着腐蚀时间进一步增加,Fe3O4层的厚度略有减小而(Fe,Cr)3O4层的厚度略有增加,而IOZ的厚度却一直近似以线性规律缓慢增加。     

304NG在超临界水中的腐蚀增重随温度的异常关系

研究了奥氏体不锈钢304NG在550、600和650℃超临界水环境下的腐蚀行为。采用扫描显微镜、X射线能谱仪、X射线衍射仪分析了氧化膜的腐蚀形貌、组织结构和成分分布。实验结果表明,试样在3种不同温度下经1000h腐蚀实验后的增重均符合幂函数规律,但650℃时的腐蚀增重与600℃时的相比大幅下降,其主要原因为在较高温时,Cr的扩散速度快,试样表面氧化膜能够维持保护性从而使疖状腐蚀分布数量减少所致。     

Investigation of the corrosion behavior of 304L and 316L stainless steels at high-temperature borated and lithiated water

The effects of temperature and dissolved oxygen on the electrochemical behavior and the oxide film formation of grades 304L and 316L stainless steels at high-temperature borated and lithiated water were investigated by means of potentiodynamic polarization, scanning electron microscopy and X-ray photoelectron spectroscopy. The results revealed that increasing the solution temperature degrades the passivity of the oxide films formed on both grades of steel and shifts their corrosion potential toward more negative potentials. The oxide films formed on the steel samples immersed into the solution containing 20 ppb dissolved oxygen (DO) showed a duplex structure, in which the inner layer was mostly a composition of Cr oxides and the outer layer mainly was a Fe oxide and Ni–Fe spinel. Only a single layer of Cr-rich oxide was observed in the oxide films formed in the solutions with the DO concentrations higher than 20 ppb. Higher amount of Cr in the oxide films formed on the type 316L compared to 304L improves the passivity of the oxide film of this grade of steel and results in a wider passive region in its potentiodynamic polarization curves.     

Microstructure and oxidation properties of 16Cr–5Al–ODS steel prepared by sol–gel and spark plasma sintering methods

The 16Cr–5Al oxide dispersion strengthened (ODS) ferritic steel was fabricated by sol–gel method in combination with hydrogen reduction, mechanical alloying (MA) and spark plasma sintering (SPS) techniques. The phase characterization, microstructure and oxidation resistance of the 16Cr–5Al–ODS steel were investigated in comparison with the Al free 16Cr–ODS steel. X-ray diffraction (XRD) patterns showed that the Al free and Al added 16Cr–ODS steels exhibited typical ferritic characteristic structure. The microstructure analysis investigated by transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS) revealed that Y–Ti–O complexes with particle size of 10–30 nm were formed in the Al free matrix and Y–Al–O complexes with particle size of 20–100 nm were formed in the Al contained high-Cr ODS steel matrix. These complexes are homogeneously distributed in the matrices. The fabricated 16Cr–5Al–ODS steel exhibited superior oxidation resistance compared with the Al free 16Cr–ODS steel and the commercial 304 stainless steel owing to the formation of continuous and dense Al₂O₃ film on the surface.     

Structural,electrical and magnetic measurements on oxide layers grown on 316L exposed to liquid lead–bismuth eutectic

Fast reactors and spallation neutron sources may use lead–bismuth eutectic (LBE) as a coolant. Its physical, chemical, and irradiation properties make it a safe coolant compared to Na cooled designs. However, LBE is a corrosive medium for most steels and container materials. The present study was performed to evaluate the corrosion behavior of the austenitic steel 316L (in two different delivery states). Detailed atomic force microscopy, magnetic force microscopy, conductive atomic force microscopy, and scanning transmission electron microscopy analyses have been performed on the oxide layers to get a better understanding of the corrosion and oxidation mechanisms of austenitic and ferritic/martensitic stainless steel exposed to LBE. The oxide scale formed on the annealed 316L material consisted of multiple layers with different compositions, structures, and properties. The innermost oxide layer maintained the grain structure of what used to be the bulk steel material and shows two phases, while the outermost oxide layer possessed a columnar grain structure.     

Corrosion behavior of heat-treated Fe-Al coated steel in lead-bismuth eutectic under loading

A protective surface alloy coating on steel surfaces can prevent steels from the heavy LBE corrosion in the LBE cooled reactor. Especially, Fe-Al alloy coating on a steel surface is effective for corrosion resistance in LBE due to the self-healing of a thin and stable Al oxide layer on the surface of the coating layer. In order to investigate the utility of the coating layer under the stress due to the hydrodynamic and thermal stress induced in the practical system. The Fe-Al coated 316SS, which was heat-treated after the coating process, was immersed in the stagnant LBE at 650 °C for 250 h with loading to investigate the corrosion behavior of the specimen with the bending stress. The Fe-Al coating layer was not corroded because of the protection by Al oxide scale which was formed on the surface of the coating layer and the interface between the coating and the matrix during the heat treatment process. The coating layer cracked elastically. The LBE penetrated into the cracks and corroded the 316SS matrix and the pre-coating layer. The matrix exhibited the dissolution corrosion caused by the preferential dissolution of Ni and the oxidation forming the Fe oxide and Cr oxide. The coating layer is effective to reduce the surface of the matrix to be corroded by LBE, and can moderate the corrosion of the depth direction.