Influence of aluminium content on retarding hydrogen transport in Fe–Al binary alloys

The electrochemical hydrogen permeation measurement was utilized to determine the effective diffusivity, permeation rate and apparent solubility of hydrogen in a series of Fe–Al binary alloys at 25°C. The experimental results reveal that both the hydrogen effective diffusivity and permeation rate in these alloys are significantly dropped when Al content is more than 15–20 at.%. The hydrogen apparent solubility in these alloys is reduced with the increment of Al content, even though their lattice parameters and strain fields in these alloys are increased. For these Fe–Al binary alloys, the retardation factor of hydrogen is mainly dependent upon Al content. Both oxide film and the degree of structural order are the major retardation factors on hydrogen transport in Fe–Al binary alloys.     

Untersuchungen zum Einfluß von Inhibitoren auf die Wasserstoffversprödung von unlegiertem Stahl in Salzsäure

Investigations on the influence of inhibitors on hydrogen embrittlement of mild steel in hydrochloric acid The influence of four commercially available inhibitors as well as their main effective components on the corrosion behaviour of mild steel in 16 and 32% hydrochloric acid was investigated by potentiokinetic polarisation measurements, electrochemically controlled measurements of hydrogen permeation and by estimating the rate of mass loss. The inhibitors showed different, yet positive effects on the inhibition of the permeation of cathodically produced hydrogen. The best results were found with benzylchinolinium chloride as inhibitor. Particularly in acids containing hydrogen sulfide propargylalcohol turned out to be a poor inhibitor of hydrogen permeation. Under these conditions the addition of propargylalcohol to quart. ammonium salts even decreased their good effectiveness as single components. The fact that the effectiveness for the inhibition of hydrogen permeation often diminished in the course of short periods was not due to a simultanous increase of the corrosion rate.     

Hydrogen permeation in Fe-40 at.% Al alloy at different temperatures

The electrochemical permeation technique for studying transport and trapping of hydrogen in Fe-40 at.% Al alloy at temperatures of 5, 25, 45 and 65 °C was used in the paper. The influence of temperature on the effective hydrogen diffusion coefficient, hydrogen permeation rate and hydrogen solubility was determined. The activation energy of hydrogen diffusion in iron aluminide in the studied temperature range was also determined.     

金属氢渗透研究综述

综述了氢渗透的研究方法和研究历史,总结了当前对氢损伤机理的研究,以及在易发生氢脆环境下的氢渗透行为规律和影响氢行为的因素。在这些研究的基础上,国内外先后开发了许多氢渗透防护技术,如:阻碍氢原子渗入基体,在材料表面制备涂镀层;消除钢中有害元素的方式,改变中氢原子陷阱的数目;从组织入手,开发高纯度、高抗氢钢,包括一些系列铁素体合金钢等。综述了从传统的电沉积阻氢合金镀层,到新工艺制备阻氢陶瓷层的发展。阻氢涂层具有阻氢性能极佳,兼具保护作用的优点,但容易失效,破损后会加快基体的局部腐蚀;而通过冶金、热处理来净化钢材,改变组织成分开发的纯净钢,其实际抗氢脆性能并不理想,仍然会出现氢引起的力学性能下降,并且具有控制工艺复杂、能耗大的缺点。由此认为,氢一旦进入金属材料内部,造成材料的性能损伤不可避免,防止氢进入金属材料是该领域的关键科学问题。氢渗透过程是氢损伤发生的关键步骤,那么阻碍氢渗透过程的进行就成了氢损伤防护措施的重中之重。抑制氢渗透过程的发生需要从降低氢原子浓度梯度、降低材料内部氢陷阱密度和结合能两方面入手,开发有效的抑氢手段,抑制氢渗透过程,使材料内部的氢原子浓度小于临界氢原子浓度。     

Hydrogen permeation behavior of nickel electroplated AISI 4340 steel

The role of the electroplated nickel layer on hydrogen permeation through AISI 4340 steel was investigated by a electrochemical hydrogen permeation test. The permeation test, composed of three steps, was conducted to measure the hydrogen diffusivity and surface hydrogen concentration. A constant current of 20 mAcm^-2 and a constant potential of -100 mV vs. Ag/AgCl electrode were applied to the hydrogen entry and exit cells, respectively. The thickness of the electroplated nickel layer on AISI 4340 steel increased in a linear fashion with an increase in electroplating time. The nickel coated layer contributed to a decrease in the hydrogen permeability of nickel coated AISI 4340 steel specimens. This is due to the fact that the surface hydrogen concentration and hydrogen diffusivity in nickel coated layer were lower than those of AISI 4340 steel substrate. Especially, low hydrogen diffusivity decreased significantly with hydrogen permeability. The critical effective hydrogen diffusivity for barrier of nickel electroplated AISI 4340 steel specimens was higher than the hydrogen diffusivity of AISI 4340 steel specimen. It is proposed then that the thin nickel layer on AISI 4340 steel acts as a barrier for hydrogen permeation through AISI 4340 steel.     

氢渗透合金膜的研究现状及发展趋势

氢渗透合金膜是一种重要的氢气提纯材料。本文简要介绍了目前存在的几种氢渗透合金膜的研究进展和各自的优缺点,重点讨论了氢渗透合金膜的工作原理、氢渗透性能和制备方法;详细分析了影响氢渗透性能的关键因素,包括氢渗透系数、氢扩散系数、氢溶解系数和氢脆性,提出了通过改善氢渗透合金膜的微观结构以提高膜材料的抗氢脆性、提高氢渗透系数和扩散系数的方法,最后对合金膜的发展趋势进行了探讨。     

Influence of tensile straining on the permeation of hydrogen in low alloy Cr-Mo steels

The effect of dynamic tensile straining on hydrogen permeation through low alloy Cr-Mo steel samples was studied with the electrochemical permeation technique. The hydrogen steady-state permeation current through large flat tensile specimens mounted between the two compartments of an electrochemical permeation cell undergoes different types of changes, depending on the charging conditions, on the steel’s composition and microstructure and on the strain rate. Dynamic trapping of hydrogen to strain-induced dislocations which leads to a deviation of the permeation current below the initial steady-state value is mostly observed when the external hydrogen activity and the strain rate are large. However, the hydrogen permeation current through Cr-Mo steels with a bainitic microstructure appears to be less sensitive to tensile straining up to large deformation levels than a lower alloyed Cr-Mo steel with a ferrito-pearlitic microstructure. On the other hand, the enhancement of the steady-state hydrogen permeation current observed during tensile straining if specific experimental conditions are met strongly suggests a mechanism of hydrogen transport by mobile dislocations which contributes to hydrogen permeation.     

Hydrogen permeation behaviour of X56 steel in simulated atmospheric environment under loading

Abstract

The hydrogen permeation behaviour of X56 steel under loading in a simulated atmospheric environment was investigated. The results show that the hydrogen permeation current increases as the elastic deformation of the steel increases. In addition, the hydrogen permeation current decreases with an increase in plastic deformation. Cracking of the passive film and the reduced specimen thickness after deformation are proposed as reasons for the decrease in permeation. Thus, during plastic deformation, there is a competition between dislocation trapping and dislocation transport of hydrogen, which affects the overall hydrogen permeation current.     

Modelling the influence of trapping on hydrogen permeation in metals

Hydrogen permeation (diffusion) is strongly influenced by the local hydrogen concentration and by the density and depth of traps. Consequently hydrogen diffusion cannot be described by a constant effective diffusivity as suggested in standards and several papers.A modelling study for diffusion of hydrogen in metals with traps is presented. Simulations are performed for a charging and discharging process, showing a remarkable asymmetry. The actual chemical diffusivity ranges over several orders of magnitude depending on the hydrogen concentration as well as the density and depth of traps. Consequently, the concept of effective diffusivity outlined in standards and many publications fails.     

氢渗透传感器及其在海洋腐蚀环境中的应用

目的探究电化学氢渗透传感器在海洋腐蚀环境中的适用性以及相应腐蚀环境下高强度钢的氢渗透行为。方法设计和制作系列氢渗透传感器,将氢渗透传感器置于海洋大气腐蚀环境、模拟浪花飞溅区腐蚀环境和模拟海洋潮差区腐蚀环境,通过电化学氢渗透技术反映自然腐蚀条件下由腐蚀导致的氢向AISI 4135高强钢材料的渗透情况。结合各腐蚀环境下影响材料腐蚀速率的因素,分析各腐蚀环境下氢产生的机理。结果海洋大气腐蚀环境下由腐蚀引起的材料的氢渗透电流密度处在一个较小的数量级,氢渗透电流的大小与大气的绝对湿度呈正比例关系;模拟浪花飞溅区腐蚀环境下,氢渗透电流的大小与模拟浪花飞溅效应的海水喷淋间隔时间相关,相较于海水喷淋间隔为1min条件下的氢渗透电流密度,喷淋间隔为10min条件下的氢渗透电流密度的最大值更大。处于模拟海洋潮差区腐蚀的材料的氢渗透电流呈现周期性波动,并且前期氢渗透电流的波动幅值较大,而后趋于稳定。结论电化学氢渗透传感器在检测大气腐蚀环境和模拟浪花飞溅、模拟海洋潮差环境下由腐蚀引起的氢渗透电流的应用中,展现了良好的稳定性和可靠性,表明了相应试验海洋腐蚀环境下氢渗透电流的特点,不同腐蚀环境下材料的氢渗透行为差异较大。     

微观组织对GCr15轴承钢氢扩散行为的影响

通过对球化退火态、球化退火+淬回火(Q&T)态GCr15轴承钢进行电化学氢渗透试验来描述氢扩散行为,并分析了微观组织以及热处理状态对氢扩散行为的影响。结果表明,对于球化退火态试样,碳化物的分布情况对氢扩散行为影响很大。氢在带状碳化物中扩散最快,而沿晶界分布的网状碳化物作为氢陷阱,可以捕捉更多的氢原子。Q&T试样中,氢在带状未溶碳化物中扩散最快,且随着残留奥氏体体积分数的增大,有效氢扩散系数减小。球化退火试验钢的氢扩散系数远高于Q&T钢。Q&T试样中残留奥氏体的存在使氢陷阱增加,导致氢的渗透更难进行。     

Sulphide stress cracking behaviour of weldments produced by indirect electric arc welding

Abstract

The aim of the present study was to evaluate the corrosion resistance of weldments produced by the Indirect Electric Arc technique. The material studied was API grade X-65 steel, which was corroded in NACE solution saturated with H₂S. Three different temperatures were employed, room temperature (25°C), 37°C and 50°C. The test methods used included potentiodynamic polarisation curves, hydrogen permeation measurements and slow strain rate tests. The anodic corrosion current density and sulphide stress cracking susceptibility of the weldments were found to be unaffected by temperature over the range 25–50°C. However, values of the steady-state hydrogen permeation current, hydrogen permeation rate, effective diffusion coefficient, and the concentration of hydrogen atoms at the entrance side all increased with temperature. The cracking of the X-65 weldments is explained in terms of a hydrogen embrittlement mechanism.     

Untersuchungen zum Einfluß des Stahlgefüges auf die instationäre Wasserstoffpermeation

Investigations on the influence of microstructure of steels on unsteady state hydrogen permeation The effect of microstructure of iron and a low alloyed steel on hydrogen permeation at room temperature is studied by means of the electrochemical permeation method. Hydrogen transport through these materials during charging or effusion processes is affected by microstructural heterogeneities and hydrogen content. The diffusivity as a function of the state of the materials ranges over about five orders of magnitude. In course of non-steady state diffusion dislocations and interfaces decrease the effective diffusivity to values between 10⁻⁷ and 10⁻⁹ cm²/s. At steady state permeation the diffusivity reaches the values of 10⁻⁵ to 10⁻⁴ cm²/s.     

钛对冷轧超低碳搪瓷钢鳞爆性的影响

在相同轧制工艺和不同退火温度条件下,研究了添加钛的冷轧超低碳钢的氢渗透性和搪瓷的鳞爆性.研究发现,含钛的钢搪瓷鳞爆现象较轻;当退火温度提高到750℃时无鳞爆出现.显微组织分析表明,含钛钢中生成了钛化物相,并且随着退火温度的提高,钛化物析出量增多.氢渗透曲线测试证明,氢穿透时间和氢陷阱系数明显高于不含钛的钢.此外,随着退...     

CO2对Pd8Y0.23Ru合金膜氢渗透性能的影响

在300~450℃范围内,研究氢中加入CO2对Pd8Y0.23Ru合金膜氢渗透性能的影响。结果表明,CO2的加入会大大降低膜的氢渗透率,CO2浓度越高,氢渗透率降低越多;CO2对Pd8Y0.23Ru合金膜存在一定的毒化作用,使氢渗透率下降,450℃下的毒化作用明显强于300℃,但随着时间的延长,渗透率降低速率趋缓。CO2降低氢渗透率还有另外2个因素:当CO2浓度较高(>3%,摩尔分数)时,聚集在膜表面附近的CO2对氢气传质的阻塞作用是氢渗透率降低的主要因素;当CO2浓度较低(<1%)时,CO2在膜表面吸附,占据氢的活性点位,是氢渗透率降低的主要因素。     

钯钇合金净化器的透氢性能研究

对微通道及传统外压式钯钇合金净化器的透氢速率和氢混合气(CO2、H2O、CO)分离性能进行了研究。结果表明，在纯氢条件下，两种结构的钯钇合金净化器透氢速率随压力的平方根差呈线性增大，并且透氢速率基本一致；在对氢混合气(CO2、H2O、CO)进行分离时，两种结构的钯钇合金净化器的透氢率发生了显著下降，但微通道结构下降不明显。     

Electrochemical investigation of hydrogen absorption in a duplex stainless steel

Hydrogen permeation through and hydrogen desorption from duplex stainless steel membranes of various thickness were studied by the electrochemical technique. During the permeation experiments, one side of a membrane was charged with hydrogen by galvanostatic cathodic polarisation in 0.1M NaOH at 25 °C. After an interruption of the hydrogen charging, the desorption rate of hydrogen was measured at both sides of the membrane. The obtained permeation and desorption rates were analysed in terms of the real values of the hydrogen diffusivity (D_α) and the length of diffusion paths (L_α) in the ferrite phase. The total amount of absorbed hydrogen consists mainly of the hydrogen dissolved in the ferrite matrix (diffusible hydrogen) and the hydrogen dissolved in the austenite phase (reversibly trapped hydrogen). Amounts and concentrations of these two forms of hydrogen were evaluated. Some peculiarities and limitations as regards the usefulness of the permeation–desorption measurements for studying hydrogen in the duplex stainless steel membranes are given.     

The hydrogen permeation investigation of API X56 steel in sea mud

It was found that the corrosion rate of steel in the sea mud with sulfate‐reducing bacteria (SRB) could be as high as 10 times of that in the sea mud without SRB. And the hydrogen permeation reaction would occur when metals were corroded. So it is necessary to investigate the effect of living SRB on hydrogen permeation in the sea mud. Cathodic potential was often added to metals in order to protect them. But hydrogen permeation could be affected by the cathodic potential. So it is also necessary to study the effect of cathodic potential on hydrogen permeation. In this paper, the hydrogen permeation actions of API X56 steel in the sea mud with and without SRB at corrosion and cathodic potential were studied with an improved Devanathan‐Stachurski's electrolytic cell. Experimental results showed that during the growth of SRB, the current density curve of hydrogen permeation was accordant with the growth curve of SRB. But the hydrogen permeation current density of API X56 steel hardly changed in the sterilized sea mud. Compared with the hydrogen permeation current density of API X56 steel in the sterilized sea mud, the hydrogen permeation of API X56 steel in the sea mud could be accelerated by living SRB. Experimental results also showed that the hydrogen permeation current density increased rapidly when the cathodic potential was added to the three‐electrode system of the cathodic cell, and then the hydrogen permeation current density could obtain a stable value slowly. So the cathodic potential added to the cathodic cell could accelerate hydrogen permeation.     

周期反向脉冲电流对电解酸洗中钢板渗氢的影响

研究了周期反向脉冲电解酸洗的工艺参数对渗氢的影响，以开发出能减少渗氢的高效电解酸洗方法，试验表明，脉冲电流酸洗的电流密度宜控制在不超过50mA/cm^2，脉冲频率宜控制在20～50Hz，这时渗氢电流可比阴极直流电解酸洗的渗氢电流大为减小，脉冲频率小于等于10Hz时，酸浓度的高低变化对渗氢影响很小。     

碳和氧在氢渗透阻挡层中的作用

为了了解氢渗透阻挡层的阻氢机理,在氢化锆表面电镀Cr-C后,再对镀层进行热处理(400℃),最后把试样在700℃的真空中保温10h.用EDS法对没有进行热处理的镀层的成分进行分析,再用X射线光电子能谱(XPS)研究氢渗透阻挡层不同深度处的化学态,并对阻挡层原子进行定量分析.结果发现:未热处理的镀层主要含有C和Cr,阻挡层中含有C、O、Cr和Zr,进行氢渗透试验(700℃保温)后的阻挡层中C-H和O-H含量都增加,前者更明显.由此可说明H因破坏C、O原来的成键方式而被C、O捕捉,C对氢渗透阻挡层的作用大于O的作用.