304奥氏体不锈钢在硝酸溶液体系中的电化学腐蚀行为

采用极化曲线测量法对304不锈钢在硝酸溶液体系中的电化学耐蚀性能进行了测试,分别研究了在硝酸溶液中添加硝酸盐、草酸、乙酸、柠檬酸等成分对304不锈钢电化学腐蚀行为的影响。结果表明,在硝酸溶液中,硝酸盐的加入能够抑制不锈钢的电化学腐蚀,而草酸能够显著增强溶液对不锈钢的电化学腐蚀能力,在硝酸和草酸溶液体系中加入1g/L柠檬酸后,自腐蚀电流由6.02μA/cm~2上升到22.8μA/cm~2,对电流腐蚀有较明显的促进作用。     

奥氏体不锈钢在MIPR模拟溶液中的腐蚀行为研究

研究了304L和321不锈钢在80℃、MIPR模拟溶液中的均匀腐蚀、晶间腐蚀和应力腐蚀行为.实验结果表明304L和321不锈钢腐蚀1 500 h后的表面腐蚀轻微,具有良好的耐均匀腐蚀性能,且无晶间腐蚀和应力腐蚀趋势.这是因为两种奥氏体不锈钢腐蚀后表面均形成了以Cr2O3为主的致密氧化膜,阻止了腐蚀的进行,表面Cr(Ⅲ)形成的外膜和内膜的协同作用提高了膜的稳定性和耐蚀性.     

核电厂换料水池304L不锈钢覆面开裂原因分析

为查明某核电厂换料水池304L不锈钢覆面开裂的原因,对其宏微观组织、化学成分、力学性能、断口形貌、腐蚀产物进行分析。结果表明:该304L不锈钢覆面的开裂属于典型的Cl-导致的应力腐蚀开裂。换料水池背部混凝土施工中使用的氯-偏共聚乳液是Cl-的主要来源。建议后续不锈钢覆面修复时必须彻底清除含氯—偏共聚乳液的混凝土层,其他类似混凝土施工中应加强水质控制和混凝土添加剂管理。     

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。     

321不锈钢在低酸度硝酸铀酰溶液中的腐蚀特性

用称量法和电化学法研究了321不锈钢在不同浓度和pH值的硝酸铀酰溶液中的高温均匀腐蚀和电化学府蚀行为。均匀腐蚀试验结果表明．在选定的腐蚀条件下，321不锈钢样品在960h内，其表面光洁度无明显变化．腐蚀速率小于0．04mg/m^2.h，在低酸度的硝酸铀酰溶液中耐蚀。用腐蚀电入学法研究了321不锈钢在有溶解氧的硝酸铀酰溶液中的腐蚀电化学特性，测量了电极的腐蚀电位、腐蚀电流密度。经AES分析表明，电化学腐蚀后的样品在腐蚀膜中有一定量的铀．深度剖析含铀腐蚀膜的厚度为10—15nm。     

不同pH值高锰酸钾对不锈钢腐蚀性能影响

采用重量法、扫描电子显微镜、动电位极化曲线法研究304L不锈钢在不同pH值高锰酸钾溶液中的腐蚀行为。304L不锈钢经过pH值为1.8的酸性高锰酸钾溶液(NP)氧化后表面腐蚀产物最多,pH值为6.5的高锰酸钾溶液(HP)氧化后表面腐蚀产物最少,pH值为12.5的碱性高锰酸钾溶液(AP)氧化后表面腐蚀产物居中。经过氧化步骤后,试样经过硝酸与抗坏血酸混合还原溶液清洗后都具有金属光泽,微观形貌区别不大。304L不锈钢在HP中的腐蚀电流密度最小,在NP和AP中的腐蚀电流密度大于HP。化学去污清洗工艺中高锰酸钾溶液对不锈钢的腐蚀性最弱,NP、AP对不锈钢基材的腐蚀性强于HP。     

酸性硫酸根离子介质中奥氏体不锈钢的应力腐蚀行为研究

用慢应变速率法(SSRT)研究奥氏体不锈钢316Ti和316NG在酸性硫酸根离子介质中的应力腐蚀(SCC)行为.结果表明在酸性硫酸根离子环境中,316Ti产生应力腐蚀的临界浓度比316NG的高,但316NG的裂纹扩展速率比316Ti大.用电化学阳极极化法比较了两种奥氏体不锈钢在酸性硫酸根离子介质中的抗腐蚀性能的差异,结合微观分析,探讨了SO2-4离子对奥氏体不锈钢的SSRT-SCC损伤机理.     

304NG不锈钢均匀腐蚀性能研究

用MARS循环腐蚀回路对304NG不锈钢进行了1500h的循环水腐蚀考验,对均匀腐蚀速率进行了定量评估。试验结果表明:在模拟核反应堆一回路循环水条件下,304NG控氮不锈钢板材、锻件的均匀腐蚀速率为1.40mg/(dm2ˇ30d)和1.91mg/dm2(dm2ˇ30d),0Cr18Ni10Ti不锈钢板材、锻件的均匀腐蚀速率为4.44mg/(dm2ˇ30d)和4.65mg/(dm2ˇ30d),304NG控氮不锈钢的均匀腐蚀速率低于0Cr18Ni10Ti不锈钢。     

钛和304L型不锈钢异种连接的腐蚀和微观组织

为了将装载高放射性和强腐蚀性硝酸溶液的Ti基加Zr基合金(Ti，Zr-2，Ti-5％，Ta，Ti-5％Ta-1．8Nb)的溶解器和核燃料后处理厂由304L型不锈钢制成的其它部件连在一起，就需要它们之间的异种连接有良好的完整性和抗腐蚀性：熔化焊方法会产生叮溶解于硝酸的二次沉淀，因此建议采用固态焊接方法。在本工作中，多种用于关键场合使Ti-304L SS连接有足够的强度、延性和抗腐蚀性的异种金属连接方法受到关注，Kalpakkam的1GCAR(印度甘地原子能研究中心)对开发工作做了规划，与三相（液相、汽相，冷凝相)腐蚀试验的结果一起，对可能的方法以及微观组织和冶金特性做了讨论。在这些结果基础上，后处理厂采用了爆炸焊方法得到的异种连接技术。     

304L奥氏体不锈钢搅拌摩擦焊与TIG焊接头的微观组织与性能

采用搅拌摩擦焊和钨极惰性气体保护电弧焊(TIG)分别对3 mm厚304L奥氏体不锈钢进行焊接,对比分析2种焊接方法下接头的微观组织和抗拉强度。304L不锈钢的搅拌摩擦焊焊接接头由焊核区、热力影响区、热影响区及轴肩变形区组成;焊核区组织为均匀细小的动态再结晶组织,热力影响区组织发生明显的塑性变形,而热影响区仅受到热的作用晶粒有所长大;TIG焊接头组织由呈胞状树枝奥氏体晶和呈蠕虫状或板条状铁素体组成。结果表明:2种焊接方法获得的接头强度相似,都略高于母材强度。     

含草酸的硝酸溶液对316L不锈钢的腐蚀行为

模拟金属材料在草酸钚沉淀母液蒸发浓缩工艺的服役条件,按GB/T 4334.3-2000要求,开展了含草酸的硝酸溶液对316L不锈钢板材和焊件的腐蚀行为研究。实验采用称重法获得了腐蚀速率数据,采用扫描电镜观察金属表面的腐蚀形貌,通过能谱分析腐蚀前后样品的表面元素分布,并测定了腐蚀溶液中金属离子的浓度。结果表明:模拟实验条件下316L不锈钢各腐蚀样品腐蚀速率较低,为均匀腐蚀。在103℃、8.0 mol/L硝酸条件下,316L不锈钢板材和焊缝的平均腐蚀速率分别为0.049 6 g/(m²·h)和0.068 6 g/(m²·h)。研究结果为草酸钚沉淀母液蒸发浓缩设备的材料选择提供了数据参考,优化焊缝工艺是316L不锈钢作为草酸母液蒸发浓缩设备材料使用重要的改进方向。     

核级304L不锈钢钎焊接头组织及耐腐蚀性能研究

核级304L不锈钢与BNi 7钎料真空钎焊接头存在晶间腐蚀行为,但工艺与钎缝耐腐蚀性能的关系尚未得到充分研究。为充分评估压水堆燃料组件结构件中不锈钢真空钎焊接头的晶间腐蚀和应力腐蚀敏感性,降低腐蚀失效风险,采用定量金相方法分析了钎缝中的化合物相含量,采用硫酸 硫酸铁法和双环动电位再活化（DL EPR）法评价了钎缝耐晶间腐蚀性能,并采用高温高压水应力腐蚀裂纹扩展试验评价了钎缝的耐应力腐蚀性能。结果表明,钎缝中化合物相含量越高,耐晶间腐蚀性能越好。且钎缝在高温高压水中存在明显的应力腐蚀开裂行为,但其与钎焊工艺的关系尚需进一步试验研究。     

Corrosion Phenomenon of Stainless Steel in Boiling Nitric Acid Solution Using Large-Scale Mock-Up of Reduced Pressurized Evaporator

To evaluate the component life in a spent nuclear fuel reprocessing plant, a large-scale mock-up test apparatus of a reduced pressurized thermosiphon evaporator was constructed, and the corrosion mechanism of a heat transfer tube made of ultralow carbon type 304 stainless steel in boiling nitric acid solution was studied. The corrosion tests were conducted for about 36,000 h, and changes in the corrosion amount and rate in the test duration were discussed. The relationships between the amount of corrosion and tube surface temperature and heat flux were investigated, and the corrosion propagation mechanism considering intergranular penetration was studied based on the observations of morphologies of corrosion surfaces and the measurements of intergranular penetration depths. After a long duration, the increases in the corrosion amount and rate saturated when intergranular penetration and grain dropping occurred by turns. This result means that a linear estimation can be applied to the life prediction for corrosion. Three portions of the tube were observed, and the amounts of corrosion were different among the three portions, but no difference in the morphology of intergranular corrosion existed. The amount of corrosion was affected by both tube surface temperature and heat flux. A large amount of corrosion could be observed in both the boiling starting portion and the top, where high tube surface temperature and heat flux were observed.     

Corrosion of Austenitic Stainless Steel in Steam Containing Cesium Hydroxide

Corrosion behavior of SUS-304L SS, which is used as a typical material for reactor structures has been studied under the steam containing CsOH at temperatures of 450~750°C. The steam was supplied by heating the aqueous solution of CsOH with concentrations 0~320 mM at 110°C. The mass gain by oxygen uptake increases parabolically with reaction time. Since the activation energy of reaction rate constant is consistent with that of self diffusion of Fe in Fe₃O₄, it can be considered that the corrosion reaction is determined by the diffusion rate of Fe atoms in the outer oxide layer. The effect of CsOH on the corrosion reaction under the steam is large in the initial stage of the reaction, but small in the final stage. The mechanism of corrosion reaction has been discussed on the basis of microstructure and composition of the reaction layers.     

电化学去污对基体材料不锈钢抗腐蚀性能的影响

研究电化学去污期间1Cr18Ni9Ti不锈钢试样单位面积质量和表面形貌的变化及去污前后试样的阳极极化曲线变化。结果表明：伴随着失重，试样表面变得光滑；电化学去污对材料抗腐蚀性能没有影响。     

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。     

碳钢对核主泵用奥氏体不锈钢的污染研究

奥氏体不锈钢在加工、运输和装配过程中如果与碳钢直接接触,就会被碳钢污染,而导致奥氏体不锈钢耐蚀性能的改变。众所周知,核主泵用奥氏体不锈钢对耐蚀性有着非常严格的要求,本文以Z2CN18-10核主泵用奥氏体不锈钢为例,通过FeCl3腐蚀试验和电化学方法测试了被碳钢污染后其耐腐蚀性能的变化。试验结果表明:附着在不锈钢表面的碳钢对其长期总体腐蚀速率影响不大;嵌入式的碳钢颗粒会显著降低奥氏体不锈钢的点蚀电位,增大发生点蚀的倾向;硝酸钝化可部分抵消被污染不锈钢点蚀电位的降低,但该值仍远低于同样经过硝酸钝化,而未被污染的不锈钢的点蚀电位。此外,还针对碳钢污染对核电站辐射场的影响和对燃料包壳热传导效率的影响进行了讨论。     

Corrosion of Type 304L Stainless Steel in Concentrated Plutonium Nitrate Solution

Dryout experiments of water have been conducted in an annulus with inside heating (heat flux from inner wall only) under high-pressure, low-flow and mixed inlet conditions which are of importance in the core thermal-hydraulic behavior during a loss-of-coolant accident (LOCA) and also partially during an anticipated transient without scram (ATWS) of a nuclear reactor. The experimental conditions have covered ranges of pressure of 3 MPa, mass flux from 105 to 320 kg/m²·s and inlet quality from 0.15 to 0.90. The dryout data have been compared with several existing empirical critical heat flux (CHF) correlations and a new correlation. The Katto correlation predicts best the CHF among the existing correlations examined. However, even the Katto correlation overpredicts the CHF by factors up to 2 at about 1/6 data points of the present dryout data. The present dryout data are divided into two groups (regions) according to the value of a non-dimensional number l _bo/d _he, where l _bo is the assumed boiling length and dh, the heated equivalent diameter. A new correlation covering both the regions has been developed by correlating the present dryout data in terms of two non-dimensional numbers. The new correlation performs best among the correlations examined in predicting the present dryout data.