Effect of Microstructure of 304L SS and Thermal Aging of 304L SS Weld on the Corrosion Behavior in Simulated High Level Waste

The effect of oxidizing ions present in simulated high level liquid waste (HLW) on the corrosion behaviour of solution annealed, sensitized 304L SS and 304L SS weld was investigated by potentiodynamic anodic polarization technique. Potentiodynamic anodic polarization studies showed a higher passivation current density and increased corrosion potential (E_corr) in simulated HLW when compared to 3 M HNO₃ in all the specimen mentioned above. In addition, the effect of microstructure of thermally aged 304L SS weld on the corrosion behavior was investigated in simulated HLW medium. Thermal ageing of 304L SS weld was carried out at 1023 K/100 h. Optical microscopy confirmed step microstructure for solution annealed and ditch microstructure for the sensitized specimens. The weld region was found to possess delta-ferrite distributed in austenite matrix. Thermal ageing resulted in fragmentation/dissolution of delta-ferrite and transformation of delta-ferrite to carbides and sigma phases. The thermally aged 304L SS weld specimen showed only a marginal decrease in corrosion resistance in simulated HLW when compared to the 304L SS weld.     

Production and Characterization of PANI/TiO2 Nanocomposites: Anticorrosive Application on 316LN SS

Conductive polyaniline/titanium dioxide (PANI/TiO₂) nanocomposites with different weight ratios were synthesized using in situ chemical oxidative polymerization. PANI/TiO₂ was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis and electrical conductivity. Room temperature conductivities of PANI, PANI/TiO₂ (I), PANI/TiO₂ (II), and PANI/TiO₂ (III) are 9.77 × 10^?4, 1.89 × 10^?5, 2.01 × 10^?5 and 2.87 × 10^?5 S/cm respectively, show decrease of conductivity with increase of TiO₂ content in the nanocomposite due to the hindrance of carrier transport between different conjugated chains of PANI in composite. The IR measurement indicates that there is strong interaction between the PANI and TiO₂ nanoparticles showing beneficial effect on the thermal stability of PANI/TiO₂ nanocomposite. Corrosion inhibition study shows that 316LN stainless steel coated with PANI/TiO₂ nanocomposite with weight ratio 0.05 shows better corrosion inhibition effect than pure PANI and nano-TiO₂ coating.     

Development of Silica Glass Coatings on 316L SS and Evaluation of its Corrosion Resistance Behavior in Ringer’s Solution

Sol-gel derived silica glasses have many promising features, including low-temperature preparation as well as chemical and physical stability. Two silica glasses with Si₁₀₀ and Si₈₀ composition were prepared to understand the factors contributing to the rate of bioactivity. The effects of pH, solution aging temperature, and molar ratio of H₂O/tetraethyl orthosilicate (TEOS) were studied, and the obtained powder sample was characterized by Fourier transform infrared spectroscopy, X-ray diffraction studies, and scanning electron microscopy. The synthesized silica glasses were deposited on 316L SS by the spin coating method at the optimized speed of 2000?revolutions per minute. The corrosion resistance behavior of the coatings was determined by (1) open-circuit potential vs time of exposure, (2) electrochemical impedance spectroscopy, and (3) cyclic polarization in Ringer??s solution. A higher breakdown potential (E _b) and repassivation potential (E _p) value with lower current density was obtained from cyclic polarization. Similar results were observed from impedance analysis with higher charge transfer resistance (R _ct) and lower double layer capacitance (C _dl) indicating the corrosion resistance behavior of the coatings compared with the uncoated 316L stainless steel. From the results, it was observed that both Si₁₀₀ and Si₈₀ glass coatings had a positive effect on the corrosion resistance behavior. An adhesive strength of 46?MPa and 45?MPa was obtained for the Si₁₀₀ and Si₈₀ coatings, respectively. An accelerated leach out study was carried out by impressing the potential at their breakdown potential to determine the effect of glass coating for long-term contact between the implant and a normal biological medium.     

成型和表面处理工艺对316L不锈钢镍释放率的影响

采用人工汗液浸泡法及火焰原子吸收光谱仪测试了316L不锈钢（/%:0.023C,17.57Cr,11.23Ni,2.03Mo）11种成型和表面处理工艺条件下的镍释放率。试验结果表明,50%压下率冷轧、1050℃固溶,镜面抛光的316L不锈钢型材镍释放率只有0.02 μg/cm²/周,很好地满足了欧盟新标准EN1811:2011的要求。但是成型工艺（冷轧态,铸态）表面处理方式（粗糙度）、取样方式（纵、横向）都会直接影响材料的镍释放率,使其提高3~26倍。     

Comparison of SS 304 LN and 316 LN as choice of structural material for primary pipe in fast breeder reactors

In pool type FBRs primary sodium pumps (PSP), operating in parallel, circulate the sodium through the core to remove the nuclear heat. The pumps suck the sodium from cold pool and supply it to a spherical header at the bottom; subsequently the sodium flows through pipes from the spherical header into the grid plate, before entering the core subassemblies. Under normal operating condition, each pipe is subjected to 0.8 MPa internal pressure of sodium flowing at 670 K. As the pipe is located in the cold pool, it is at an isothermal temperature of 670 K during normal operation. The pipe is subjected to hot shock during two thermal transients Viz. offsite power failure (160 times) and loss of Steam water system (47 times). Both these events lead to Safety Grade Decay Heat Removal (SGDHR) operation and the cold pool reaches 791 K during offsite power failure and 816 K during loss of steam water system. Even though the normal operating temperature for the primary pipes conveying sodium from spherical header to grid plate is below creep regime, creep damage occurs due to the governing hot shocks discussed above. One of the criteria for selecting the material is the creep fatigue damage for the longer design life (40 years for the Prototype Fast Breeder Reactor under construction and 60 years for the future reactors). The material choice for out of core reactor assembly components are generally austenitic stainless steels (SS316LN or SS304LN) except for the top shield. In this paper, the choice between SS 304 LN Vs SS 316 LN for primary sodium pipe with respect to the governing failure mode of creep-fatigue interaction is addressed.     

Microstructure,Surface Characterization,and Electrochemical Behavior of New Ti-Zr-Ta-Ag Alloy in Simulated Human Electrolyte

Metallurgical and Materials Transactions A - A new Ti-20Zr-5Ta-2Ag alloy was elaborated and characterized regarding its microstructure, its native passive film composition and thickness, its...     

The Influence of Zirconia Stoichiometry on the Morphology of Thin Metal Films Deposited on its Surface After Annealing in Vacuum

Powder Metallurgy and Metal Ceramics - Thin metal films deposited on a nonmetallic material can become fragmented in heating. The higher the adhesion in the contact pair, the lower the tendency to...     

Effects of Nitrogen Flow Rate on the Performances of Cathodic Arc Deposited TiN Films on 316L Stainless Steels as Bipolar Plates for the Proton-Exchange Membrane Fuel Cell

The corrosion resistance, interfacial contact resistance (ICR), and hydrophobicity of cathodic arc deposited TiN films on 316L stainless steels at different nitrogen flow rates as bipolar plates (BPs) for the proton-exchange membrane fuel cell (PEMFC) are investigated. It is shown in the results that the TiN-coated 316L stainless steel prepared at a moderate nitrogen flow rate (250 sccm) exhibits a low stable corrosion current density of 6.5 × 10⁻⁸ A cm⁻² in the simulated corrosive cathode environment of PEMFC, and a low ICR of 8.94 mΩ cm⁻² at a pressure of 1.38 MPa after corrosion, meanwhile presents a good hydrophobicity before and after corrosion. These results are discussed by considering the probable effects of the nitrogen flow rate on the substrate/coating system based on the microstructural characterization of the substrate/coating interface and the coating, which shows that the interdiffusion will be started in the deposition process and a moderate nitrogen flow rate during the coating process will promote to the broadening of interface region and lead to the formation of a robust and high-quality coating with fewer defects that can effectively improve the performances of the 316L stainless steel substrate as the BP for PEMFC.     

Characterization of Passive Film Formed on AISI 316L Stainless Steel after Magnetoelectropolishing in a Broad Range of Polarization Parameters

The aim of the paper is to present the changes in the surface film composition on AISI 316L stainless steel (SS) after electropolishing (EP) and magnetoelectropolishing (MEP) in a broad range of the process conditions. The X‐ray photoelectron spectroscopy surface analyses were performed to reveal the effect of MEP. The EP process has been performed under natural convection (in a stagnant electrolyte), much above the polarization plateau. A series of experiments were carried out on AISI 316L SS samples in accordance with the five‐level composite rotary statistical plan with the variables being the magnetic field intensity B (mT), and the anodic current density i (A dm^?2). XP high resolution spectra have been obtained on AISI 316L SS surface concerning Fe 2p, Cr 2p, O 1s, S 2p, P 2p, and C 1s, respectively. The Cr:Fe ratio regarding both metallic M and compound X was also studied and calculated. At the end, the summary results of Cr/Fe = f(B, i) in relation to the corrosion potential, have been compared. The conclusions, concerning the selection of MEP process conditions, regarding the optimum Cr/Fe ratio and corrosion behavior, have been formulated. It was found the Cr:Fe ratio well correlates with the pitting corrosion potential. MEP process can modify not only the rate of dissolution to a determined extent, but also control the corrosion behavior and Cr:Fe ratio results.     

Effects of Nd:YAG Pulsed Laser Welding Parameters on the Electrochemical Corrosion Properties of Carbon-Coated 316L Foils in a Simulated PEMFC Environment

Recently, PEM fuel cell bipolar plates made of carbon-coated AISI 316L austenitic stainless steel have attracted a lot of attention. Parameters suitable for Nd:YAG pulsed laser welding on the lap joint were evaluated in a simulated fuel cell environment for the first time in this study. To this end, the parameters: peak power, pulse duration, and frequency, were optimized using the response surface methodology, and a second-order polynomial was developed to predict the trend of corrosion current density. The potentiodynamic corrosion evaluation proved that with a decrease in pulse duration from 3.5 to 1.5 ms, a decrease in peak power from 650 to 130 W, and a decrease in frequency from 20 to 12 Hz occurred. Corrosion current density decreased by 76%, 34%, and 18%. According to the potentiostatic test, the optimum conditions, i.e., a peak power of 130 W (at 2.5 ms) and pulse duration of 1.5 ms (at 390 W), were achieved at anodic current densities of 0.77 µA/cm2 and 0.61 µA/cm2, respectively.     

Synthesis and Characterization of Zinc/Polypyrrole Nanotube as a Protective Pigment in Organic Coatings

This study deals with the synthesis and characterization of zinc/polypyrrole nanotube (Zn/PPy) as a protective pigment in organic coatings. The PPy nanotube is synthesized by chemical oxidative polymerization, and zinc nanoparticles are deposited onto the surface of the synthesized PPy nanotube in the presence of sodium dodecyl sulfate. Field emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction results confirm the existence of the nanotube morphology and the zinc nanoparticles. Electrochemical impedance spectroscopy and potentiodynamic polarization are performed on steel plates coated with polyvinyl butyral incorporated with the Zn/PPy nanotube. The results show that the existence of zinc can improve the protective properties of the pigment. The existence of zinc leads to a cathodic protection and the main product of zinc corrosion is the stale zinc hydroxide which can block the pores in the coating. In addition, the zinc nanoparticles can increase conductivity of the PPy nanotube leading to increasing nanotube’s ability to form protective layers of metal oxides on the steel surface.     

辐照温度对SUS316L不锈钢中二次缺陷及肿胀的影响

利用超高压电子显微镜分别在350、400、450以及500 ℃下对SUS316L奥氏体不锈钢进行剂量为3.6 dpa的电子束辐照,通过观察和分析辐照后样品中的空洞和位错环数量密度以及肿胀率,讨论了不同温度下电子束辐照对材料肿胀率的影响。结果表明,不同温度下,样品中都产生二次缺陷,如位错环和空洞;空洞引起辐照肿胀;在350～450 ℃范围内,肿胀率随着温度升高而增加,并在450 ℃达到最高;450 ℃后,肿胀率降低。不同温度下,两种二次缺陷对于点缺陷的尾闾强度不同,肿胀率与位错环、空洞在显微组织中所占比例有关。试验研究辐照肿胀率与二次缺陷间的关系,为进一步理解辐照肿胀机理、寻求抑制辐照肿胀的方法提供依据。     

双相钢中铝含量对表面氧化物及抑制层形貌的影响

 对3种不同铝含量的热镀锌双相钢进行连续退火镀锌模拟试验。研究表明：wAl=009%的双相钢表面的氧化物形貌为颗粒状和长条状的氧化物;XPS分析表明,这两种氧化物为MnO和Cr2O3。含铝wAl=012%的双相钢表面均匀分布扁平状的氧化物,氧化物平均直径为1262nm。含铝wAl=04%的双相钢表面为细小弥散分布的氧化物,平均直径为707nm。除了MnO和Cr2O3,这两种双相钢表面还生成了Al2O3。Fe-Al抑制层晶粒之间的空隙程度随着铝含量的增加逐渐变大,抑制层的致密度下降,其中含铝wAl=04%的双相钢表面的抑制层晶粒粗大。从表面氧化物与锌液有效铝之间反应的角度出发解释了抑制层形貌的变化。     

环境对316L钢塑性疲劳短裂纹萌生与扩展行为的影响

研究在对称恒幅塑性应变（Ｒ＝－１，△εＰ＝２×１０－３控制下，真空条件及温度效应对３１６Ｌ钢的塑性疲劳短裂纹萌生和扩展行为的影响。通过观测表面主裂纹长度及裂纹密度随循环周次发展规律给出材料表面损伤的定量分析。结合对表面主裂纹长度与深度的分析建立起疲劳短裂纹前沿扩展速率与循环Ｊ积分及基于塑性应变控制下等效应力强度因子的关系。     

薄板坯连铸结晶器内流动传热行为的研究

基于珠钢CSP薄板坯连铸机设备工艺条件和所采用扁平浸入式水口结构,结合铜板测温导出的热流密度分布进行了漏斗形结晶器内钢水流动、自由液面以及传热凝固等冶金现象的综合描述和数值分析.结晶器熔池中以两个上旋涡为主的钢水循环流动局限在漏斗形结晶器内,上旋涡流股冲击和离开熔池液面分别对液面起伏波动有所贡献,弯月面下距窄边100 mm范围内有二次涡形成.除水口下方两侧存在两个具有明显过热的高温区外,熔池中绝大部分钢水的温度在液相线附近保持恒定,铸坯表面温度分布和坯壳发育过程均反映出水口高温射流的影响,铸坯表面最高温区位于熔池液面下方靠近结晶器窄边的地方.     

喂钙量与软吹氯对316L不锈钢中夹杂物的影响

采用20 t电弧炉-AOD-LF-铸锭的生产工艺制备316L不锈钢,并通过LF钙处理与底吹氩的方法降低钢中夹杂物含量。其中喂钙量通过经验参数与热力学计算相结合的方法确定。运用金相显微镜及扫描电子显微镜分析了LF钙处理比例系数（实际喂Ca量/理论喂Ca量）1.65和2.95及喂Ca后软吹时间对钢锭中非金属夹杂物组成、分布及尺寸的影响。结果表明,316L不锈钢钙处理比例系数约为2.95,钙处理后钢液中夹杂物主要为铝酸钙类化合物和硅酸盐类化合物;延长软吹时间对于大尺寸夹杂物的去除效果显著;在0～25 min,随着软吹时间的延长,钢锭中夹杂物的数量减少,平均尺寸减小,最优的软吹时间为20 min。