Ti35合金在沸腾硝酸中钝化膜及过渡层形成及组成分析

研究了Ti35合金在8 mol/L沸腾浓硝酸中腐蚀240 h后表面钝化膜及过渡层的相结构。采用扫描电子显微镜(SEM)、原子力显微镜(AFM)、X射线衍射(XRD)和X射线光电子能谱(XPS)对Ti35合金腐蚀后样品的钝化膜和过渡层形貌、相结构等进行分析。研究结果表明,Ta原子优先与硝酸反应,钝化膜最终产物Ti O2和Ta2O5是通过逐步的化学反应形成的,Ta元素的加入能有效改善钛合金的耐硝酸腐蚀性能。     

Ti-Ta合金在硝酸中电化学腐蚀研究

以8 mol/L硝酸溶液为腐蚀介质,对Ti-6Ta和Ti-32Ta合金进行极化曲线和交流阻抗谱测试,并与TA2纯钛进行对比,研究不同Ta含量钛合金的电化学性能差异。结果表明,加入6%的Ta元素后,合金的腐蚀电流密度比TA2纯钛降低了近一半;加入了32%的Ta元素后,合金的自腐蚀电位提高,腐蚀电流密度比TA2纯钛降低了66%;Ti-6Ta和Ti-32Ta合金腐蚀后表面氧化膜均为单层结构;添加Ta元素可以极大地提高钛合金的电荷转移电阻,使相位角升高、变宽,增强耐腐蚀性能。     

Ta元素对TA23合金显微组织及腐蚀性能的影响

利用金相显微镜、X射线衍射仪、显微硬度仪和电化学工作站研究了微量Ta元素对TA23合金显微组织、物相、维氏硬度及腐蚀性能的影响。结果表明,加入Ta元素之后,初生α相比例有不同程度的增大,且次生α相比例明显减少;对含Ta双态组织TA23合金进行X射线衍射谱分析发现没有出现新的衍射峰,即合金中无新相生成。当合金中Ta含量为0.5%时,(10-11)α的峰强度明显增高,织构更明显;通过显微硬度测试发现双态组织TA23合金的硬度出现下降,这主要是Ta元素加入后,合金中塑性较好的初生α相比例增大导致。对双态组织TA23合金进行动电位极化曲线测试,发现加入微量Ta元素之后合金的自腐蚀电位增高,自腐蚀电流密度下降,耐腐蚀性能提高,Ta元素的加入降低了钛合金的阳极活性。当Ta含量为0.5%时,初生α晶粒尺寸增大,减少了腐蚀原电池的形成,提高了钛合金在海水中的耐腐蚀性能。     

生物医用β型Ti-25.6Nb-19.4Ta合金设计与微观结构的研究

利用钛合金β稳定系数Kβ设计制备了4种具有不同组元和成分的医用钛合金,4种钛合金的Kβ值均在1.0～1.5之间,属于理论上的近β型钛合金。通过X射线衍射分析和背散射电子衍射分析,从4种合金中优化出均匀合金化的3元β型医用Ti-25.6Nb-19.4Ta(%,质量分数)合金。利用硬度测试、压缩实验与透射电子显微镜(TEM)等手段对Ti-25.6Nb-19.4Ta合金在铸态、固溶态和400℃不同时间时效处理后的性能和微观结构进行了测试与分析,结果显示:Ti-25.6Nb-19.4Ta合金经过400℃时效处理后,其硬度、强度、弹性模量等随α相、ω相的析出变化明显。对这些变化的分析,揭示了合金的性能与显微结构的密切关系。     

合金元素对Ti-5Ta合金耐硝酸腐蚀性能的影响

研究了Cr、V、Mo、Al等元素对Ti-Ta系合金在6mol/L沸腾硝酸中腐蚀行为的影响规律。通过扫描电子显微镜（SEM）和电化学工作站等分析方法对不同成分合金的腐蚀速率、钝化膜形貌、极化曲线等进行分析。结果表明，单独添加Cr、V、Mo元素对Ti-Ta合金的耐蚀性能影响较小，而添加Al元素会大幅降低合金耐蚀性能；Ti-Ta-Cr合金的腐蚀速率最低，钝化膜致密度最高，稳定性最佳；Ti-Ta-Al合金在腐蚀过程中很难形成致密且稳定的钝化膜。对于Ti-Ta系多元合金，复合添加Cr、V元素有助于获得致密的钝化膜，添加Mo元素会降低钝化膜致密度和稳定性，Al元素添加量为1%（质量分数）时对合金钝化行为的影响不大。提高氧浓度会恶化Ti-Ta-X三元合金在沸腾硝酸中的耐蚀性能。     

在沸腾氯化镁溶液中不锈钢的电化学行为

本文通过18-8-0.5Ti不锈钢,3RE60双相钢,及单金属Fe,Ni,Cr,Mo,Ti等在沸腾42％MgCL_2溶液中的电化学测量和表面俄歇能谱分析,证实(1)在沸腾42％MgCl_2溶液中,不锈钢表面形成了钝化膜而不是Ni的富集膜(2)铬在钝化膜内层的富集反映了合金化的铬和单质金属铬的电化学行为不同,显然,在沸腾42％MgCl_2中合金中的含铬氧化物钝化膜比单质金属铬的氧化物膜更具保护性。     

锌和镀锌钢的稀土表面改性

通过在Ce(NO_3)_3水溶液中对锌和电镀锌钢进行化学转化(钝化)处理,在试样表面形成了铈转化膜。利用电子探针显微分析(EPMA)、X射线光电子能谱(XPS)和X射线衍射(XRD)等研究了转化膜的形貌、成分和结构,探讨了锌表面铈转化膜的形成机理。在氯化钠溶液中测定了试样的腐蚀率、极化曲线和电化学交流阻抗谱(EIS)等腐蚀性能参量,并与未钝化和普通铬酸盐钝化试样的情况作了对比。结果表明,本实验得到的锌表面稀土转化膜主要是由CeO_2、Ce_2O_3和ZnO组成的复合氧化物膜,铈转化膜的存在阻碍了锌在电化学腐蚀过程中的阴极反应和阳极反应,导致电荷传递电阻增大,腐蚀率降低。在一定条件下,铈转化膜对锌和镀锌钢的肪蚀效果优于铬酸盐转化膜。     

放电等离子烧结温度对Ti-13Nb-13Zr合金在人工模拟体液中耐腐蚀性能的影响

利用放电等离子烧结技术(spark plasma sintering,SPS)制备Ti-13Nb-13Zr(TNZ)生物医用合金,采用开路电位、动电位极化曲线、电化学阻抗谱和X射线光电子能谱等研究烧结温度对合金在Hank’s人工模拟体液中电化学腐蚀性能的影响,并与纯Ti(TA1)和Ti-6Al-4V(TC4)合金进行对比。结果表明:与TA1和TC4合金相比,SPS制备的TNZ合金具有较高的自然腐蚀电位Ecorr、较低的极化电流密度icorr以及较高的线性极化电阻Rp,并随烧结温度升高,耐腐蚀性能逐渐增强。该合金在模拟人工体液中耐腐蚀性能优异的主要原因是合金表面形成稳定、均匀且保护性更强的复合氧化物钝化膜,钝化膜由Ti O2,Nb2O5和Zr O2组成;随烧结温度升高,合金获得较高的致密度和近β型单相组织,耐腐蚀性能提高。     

Cu-Cr合金在3.5%NaCl溶液中腐蚀的研究

利用金相、X射线衍射、扫描电镜及电化学方法，研究了Cu-Cr合金在3．5％NaCl溶液中的腐蚀行为。结果表明：Cu-Cr合金在3．5％NaCl溶液中的腐蚀产物主要是CuO、Cu2O和铬的氧化物。溶液温度越高，其腐蚀速度越快，且在20％时，其阳极极化时出现钝化，随温度的升高，其钝化倾向减小。     

钨铜合金化学镀镍磷镀层腐蚀行为的研究

采用浸渍失重试验法和动电位极化曲线研究了钨铜合金镀层基材和钨铜合金表面化学镀Ni-P合金镀层在不同腐蚀介质溶液中的腐蚀行为。结果表明:化学镀Ni-P合金在质量分数为3.5%NaCl溶液、人工模拟汗液和体积分数为10%H2SO4溶液中的耐蚀性能好于钨铜合金;化学镀Ni-P合金浸入质量分数为3.5%NaCl溶液后其表面便开始形成钝化膜,但此钝化膜不完整,随着浸泡时间的延长,钝化膜不断生长,能在较长时间内(29d)对钨铜合金起到保护作用。     

Structural Analysis,Electrochemical Behavior,and Biocompatibility of Novel Quaternary Titanium Alloy with near β Structure

This article analyses the microstructure, electrochemical behavior, and biocompatibility of a novel Ti-20Nb-10Zr-5Ta alloy with low Young’s modulus (59 GPa) much closer to that of bone, between 10 and 30 GPa, than Ti and other Ti alloys used as implant biomaterial. XRD and SEM measurements revealed a near β crystalline microstructure containing β phase matrix and secondary α phase, with a typical grain size of around 200 μm. The corrosion behavior in neutral Ringer solution evidenced: self-passivation behavior characterizing a very resistant passive film; an easy passivation as a result of favorable influence of the alloying elements Nb, Zr, and Ta that participate with their passive oxides to the formation of the alloy passive film; low corrosion and ion release rates corresponding with very low toxicity. In MEM solution, the novel alloy demonstrated very high corrosion resistance and no susceptibility to localized corrosion. Biocompatibility was evaluated on in vitro human osteoblast-like and human immortalized pulmonary fibroblast cell (Wi-38) lines and the new Ti-20Nb-10Zr-5Ta alloy exhibited no cytotoxicity. The new Ti-20Nb-10Zr5Ta alloy is a promising material for implants due to combined properties of low elastic modulus, very low corrosion rate, and good biocompatibility.     

Corrosion-Resistant Ti-<Emphasis Type="Italic">x</Emphasis>Nb-<Emphasis Type="Italic">x</Emphasis>Zr Alloys for Nitric Acid Applications in Spent Nuclear Fuel Reprocessing Plants

This article reports the development, microstructure, and corrosion behavior of two new alloys such as Ti-4Nb-4Zr and Ti-2Nb-2Zr in boiling nitric acid environment. The corrosion test was carried out in the liquid, vapor, and condensate phases of 11.5 M nitric acid, and the potentiodynamic anodic polarization studies were performed at room temperature for both alloys. The samples subjected to three-phase corrosion testing were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX). As Ti-2Nb-2Zr alloy exhibited inferior corrosion behavior in comparison to Ti-4Nb-4Zr in all three phases, weldability and heat treatment studies were carried out only on Ti-4Nb-4Zr alloy. The weldability of the new alloy was evaluated using tungsten inert gas (TIG) welding processes, and the welded specimen was thereafter tested for its corrosion behavior in all three phases. The results of the present investigation revealed that the newly developed near alpha Ti-4Nb-4Zr alloy possessed superior corrosion resistance in all three phases and excellent weldability compared to conventional alloys used for nitric acid application in spent nuclear reprocessing plants. Further, the corrosion resistance of the beta heat-treated Ti-4Nb-4Zr alloy was superior when compared to the sample heat treated in the alpha + beta phase.     

Effect of pH on Semiconducting Property of Passive Film Formed on Ultra-High-Strength Corrosion-Resistant Steel in Sulfuric Acid Solution

Because Cr9Ni5MoCo14 is a new ultra-high-strength corrosion-resistant steel, it is important to study its corrosion behavior in sulfuric acid solution, which is used to simulate the aggressive environment. The effect of pH on the electrochemical and semiconducting properties of passive films formed on ultra-high-strength corrosion-resistant steel in sulfuric acid solution was investigated by means of the potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis, and X-ray photoelectron spectroscopy (XPS). The results indicated that Cr9Ni5MoCo14 steel showed a passive state in acid solutions. The corrosion behavior of this Cr9Ni5MoCo14 alloy was influenced by the passive film formed on the surface, including thickness, stability, and partitioning of elements of the passive film. The passive current density decreases with increasing pH, and the corrosion resistance was enhanced by the increasing thickness and depletion of the defects within the passive film. Moreover, an enrichment of chromium (primarily the oxides of Cr) and depletion of iron in the passive film led to improved corrosion resistance. These results can provide a theoretical basis for use of this alloy and further development of ultra-high-strength corrosion-resistant steel in today’s society.     

Ti35合金焊接接头在高温硝酸中的腐蚀性能研究

以沸腾的核乏燃料后处理模拟料液及空白硝酸溶液为腐蚀液,研究了Ti35合金焊接接头的耐腐蚀性能。在模拟料液中对Ti35合金熔敷金属及焊接热模拟样进行全浸腐蚀实验,间接评价了焊接接头熔区及热影响区的耐腐蚀性能。结果表明:Ti35合金焊接接头在沸腾空白硝酸溶液及模拟料液中均具有良好的均匀腐蚀性能,焊缝熔区及热影响区的腐蚀速率大于焊接接头的腐蚀速率,焊接接头的腐蚀对焊接应力的敏感性不高;在沸腾空白硝酸介质中,硝酸浓度对焊接接头的耐蚀性能有较大的影响,随硝酸浓度的提高,焊接接头的耐蚀性能有所下降;硝酸溶液中氧化性金属阳离子对Ti35合金的焊接接头具有缓蚀作用。     

Ti-6Ta合金等离子焊焊接接头的组织与性能

采用等离子弧焊对3mm及12mm厚Ti-6Ta合金板材进行了焊接实验,通过光学显微镜和腐蚀试验研究了焊接接头的组织形貌和耐腐蚀性能,同时测试了焊接接头的力学性能和弯曲性能。结果表明：采用等离子弧进行焊接的Ti-6Ta合金,其焊接热影响区为粗大的等轴晶粒,焊接熔区晶粒组织则呈粗大的不规则形貌。并且,Ti-6Ta合金等离子焊焊接接头的强度和弯曲性能与母材相当,塑性稍有下降。此外,焊接热应力对接头的强度和弯曲性能影响较小,焊接接头在沸腾硝酸中具有良好的耐腐蚀性能,且焊接接头的耐蚀性对焊接热应力不敏感。     

Corrosion Behavior of Nitrogen Containing Hot Rolled 304LN in Nitric Acid Medium

The corrosion behaviour of 304LN stainless steels containing three different nitrogen content (0.132, 0.193, 0.406 wt% N) was investigated by potentiodynamic anodic polarization technique, in 1, 4, 6 M nitric acid and simulated high level waste (HLW) medium. The results showed that all three alloys exhibited good corrosion resistance in nitric acid and simulated HLW and the corrosion properties were found to be similar. Owing to the spontaneous formation of the protective chromium oxide passive film in nitric acid and simulated HLW, increasing the nitrogen content of the alloy did not indicate any discernable effect on the corrosion resistance in both media. It was also found that the oxidizing ions present in simulated HLW did not deteriorate the passive film stability of the nitrogen containing alloys. In chloride medium, the highest nitrogen content 304LN stainless steel showed a profound increase in pitting corrosion resistance when compared to the lower nitrogen content alloy. Optical and scanning electron microscopy was carried out to obtain information about the microstructure. The results of the investigation are discussed in the paper.     

Involvement of tachykinins in endotoxin-induced airway hyperresponsiveness

Three new titanium alloys with Zr, Nb, Ta, Pd and In as alloying elements were developed and compared with currently used implant metals, namely, pure Ti and Ti-6Al-4V alloy, in terms of mechanical and corrosion properties, and cytotoxicity. New alloys showed comparable mechanical properties with that of the Ti-6Al-4V alloy, but increased corrosion potential, somewhat decreased breakdown potential and increased corrosion rate. There were no significant differences in cell growth on the surface of the various metal specimens, indicating that the cells cannot differentiate between the passivated surfaces of the various Ti metals.     

Ti–5Ta–1.8Nb: An Advanced Structural Material for High Performance Application in Aggressive Oxidising Environments

It is well known that Ti and Zr based alloys are best suitable for oxidizing environments due to their superior corrosion resistance. This has been exploited in the development of the ternary Ti?CTa?CNb alloy, for the dissolver in a fast reactor fuel reprocessing plant, the efforts of which are summarized in the present overview. Closing of fuel cycle is a priority for the three stage nuclear power program of India, towards which, indigenous development of reprocessing technology and materials is an important milestone. Corrosion resistance of structural materials controls the operating life of the dissolver in a nuclear reprocessing plant, where the spent nuclear fuel is dissolved in highly oxidizing boiling nitric acid. A complete physical metallurgy database of the alloy has been generated to understand the various phase transformations and the resultant microstructures. Corrosion control in different phases of nitric acid is achieved through microstructural optimization and the mechanisms of corrosion are understood using a detailed study of passive oxide film. The dependence of transformation texture on the mode of deformation and the role of severe plastic deformation on mechanical properties have been elucidated. These extensive R&D efforts resulted in a complete understanding of the metallurgy the alloy, which is discussed in this overview.     

Corrosion Behavior of Sensitized 304 SS in Nitric Acid Medium Containing Oxidizing Ions

The corrosion behavior of 304 stainless steel (SS) in the as-received and sensitized conditions has been investigated at room temperature and at 60 °C in the presence of oxidizing ions in 6 and 8 M nitric acid media. Corrosion of 304 SS in nitric acid was far more severe in sensitized condition than in as-received condition. Further, decrease in corrosion resistance was observed with increase in the temperature of nitric acid. The corrosion potential shifted to noble direction with increase in the concentration of nitric acid and the potential shifted further to transpassive potential at 60 °C. Increase in corrosion potential towards transpassive domain led to severe intergranualar attack. Impedance spectra showed two time constant which could be attributed to the redox reaction on the surface of oxide film. However, the effect of oxidizing metal ions was not prominent.     

Electrochemical and surface studies on zircaloy-4 exposed to concentrated nitric acid medium

Zircaloy-4 has been considered as a candidate material for dissolver and evaporators in nuclear fuel reprocessing plants involving nitric acid of high concentrations at high temperatures. The present work deals with the electrochemical studies and surface analysis of passive films on zircaloy-4 and its welds in 11.5 M nitric acid medium. Potentiodynamic polarization technique was employed to study the corrosion behaviour of the alloy in both base and welded (Manual TIG and electron beam (EB) welding) conditions. The polarization curves for zircaloy-4 and its welds exhibited a distinct breakdown of passivity at 1.5 V (SCE) and repassivation, after showing a region of stable passivation. The characterization of passive films by SEM, XRD and LRS, grown at different potentials in 11.5 M nitric acid are presented. The surface morphology and phase analysis of passive films grown at higher potentials showed the presence of monoclinic ZrO₂. The phases present in the passive film grown electrochemically in 11.5 M nitric acid at 2.0 V and by autoclaving are found to be similar. The presence of characteristic 1040 cm⁻¹ Raman peak from the sample passivated at 1.2 V indicate that the oxide present consist of nanometer size grains of monoclinic zirconia.