镀锌螺栓的断裂分析

镀锌螺栓在组装后放置1～2d于根部或头部发生大量断裂,采用化学成分分析、金相检验、硬度检测及断口分析等方法对螺栓的断裂性质及断裂原因进行了分析。结果表明：螺栓断裂为典型的氢脆断裂;主要原因是螺栓在后期酸洗和电镀过程中除氢不彻底,吸入了大量的氢;次要原因是热处理工艺控制不当,使螺栓心度硬度偏高,增加了其对氢脆的敏感性;两者共同作用最终导致螺栓发生氢脆断裂。     

电镀氢脆故障及应对措施

电镀过程中作为阴极的被镀零件在获得镀层的同时在零件金属内部也渗入了氢,如果该零件金属对氢脆敏感、又有拉应力存在时便可能发生氢脆,使零件断裂,甚至诱发事故.介绍了几例典型的氢脆故障,结合实例分析指出,渗入金属内部的氢是可逆氢,可以通过加热烘烤排出,以避免事故发生.     

ZnNi – Beschichtung hochfester Bauteile aus Stahl

ZnNi – Plating of high strength steel components Pre‐treatment and electroplating as well as post‐plating treatment of especially low alloyed high tensile strength steel components can be followed by a delayed hydrogen‐induced fracture known as hydrogen embrittlement. The entire coating process has to be controlled to avoid any failure. Most important is, that atomic hydrogen being evolved during the coating process and penetrating into the base metal after all shows an subcritical concentration within the system with respect to the mechanism of hydrogen embrittlement. Generally this will be obtained by a suitable post‐plating heat treatment of the coated components. There is evidence however that under special conditions for ZnNi – plating from alkaline solution this is not necessary. Results are reported concerning the nucleation and crystal growth and the hydrogen diffusion through ZnNi‐deposits. Further on hydrogen depth profiles of coated components and their mechanical properties will be presented and discussed.     

Causes of damages to fan blades of the generator of a steam turbine

It is shown that the fracture of blades of the fan of a TGV-200 generator is induced by corrosion fatigue intensified by residual hydrogen accumulated in steel in the process of electroplating of a cadmium coating on the surface of blades. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 3, pp. 109–112, May–June, 1997.     

Evaluation on fatigue strength of AISI 4340 steel aluminum coated by electroplating and IVD processes

In spite of toxicity, hydrogen embrittlement susceptibility, and environmental issues, cadmium electroplating is usually applied on high strength AISI 4340 aeronautical steel due to its efficient protection against electrochemical corrosion. Ion vapor deposition (IVD) process with pure aluminum also offers good protection against corrosion with the advantages of decreasing hydrogen embrittlement susceptibility and improving the fatigue strength of metallic components. In this research, the effects of aluminum electroplating and IVD aluminum coating on the rotating bending fatigue strength of AISI 4340 steel were evaluated in comparison with cadmium electroplated specimens. Experimental fatigue results showed that both aluminum electroplating and IVD aluminum coatings are possible alternatives to cadmium electroplating.     

Strength of Alloys Based on Iron,Nickel, and Titanium in High-Pressure Hydrogen

The influence of high-pressure hydrogen at room temperature on the static and fatigue properties of corrosion-resistant materials based on iron and nickel is compared for different types of loads. The sequence of characteristics can be arranged in the order of increase in the influence of hydrogen as follows: fatigue limit, ultimate strength of specimens with concentrators, relative elongation of smooth specimens, fracture pressure for a membrane under biaxial tension, percentage reduction of the area of smooth specimens, percentage reduction of the area of specimens with concentrators, and low-cycle durability. The dependences of the intensities of true stresses on the intensities of true strains (in uniaxial and biaxial tension) reveal the difference between the curves plotted in air and in hydrogen. The diagrams of hydrogen resistance taking into account the strain rates are presented. The sequence of investigated types of steel and alloys can be arranged in order of decrease in the low-cycle hydrogen resistance as follows: annealed stable austenitic and iron-nickel alloys, nitrided Cr-Ni-Mn steels, titanium alloys of the Ti-Al-Sn and Ti - Al -V systems, steels with nonstabilized austenite, high nickel alloys, maraging steels, and ferritic steels. The micromechanism of hydrogen fracture is characterized by the presence of a great number of microstructural fracture sites (bulk damage) and the completeness of local plastic relaxation. New procedures aimed at increasing the hydrogen resistance of steels and alloys are proposed, namely, the thermocyclic annealing with shot-term overheating, additional compression (with an optimal value of about 20%), and changing the temperature of aging.__________Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 6, pp. 7–18, November–December, 2004.     

沉淀强化奥氏体合金的氢致断裂行为

研究了未充氢和热充氢沉淀强化奥氏体合金的拉伸断裂行为,分析了其氢脆敏感性与拉伸断裂行为间的联系,研究了氢对合金局部塑性变形及微裂纹形核的影响。结果表明:氢使沉淀强化合金由单一的韧窝断裂转变为韧窝断裂、沿晶断裂和滑移带开裂的混合断裂方式。其原因是:一方面,氢促进位错平面化滑移趋势、加剧局部塑性变形;另一方面,滑移带被晶界、孪晶界以及不同取向的滑移带所阻碍,引起了位错塞积和氢聚集。     

电沉积Ni-P合金的制备与性能研究

本文研究了 Ni-P 合金电沉积中镀层含 P 量与其结晶状态的关系,对非晶形成进行了理论分析,并讨论了电沉积基体与溶液值对电沉积效果的影响。同时还研究了电沉积非晶膜的防渗氢作用及电沉积过程对基体力学性能的影响。     

THE EFFECT OF HYDROGEN ON FATIGUE AND DISLOCATION BEHAVIOR OF AN α/β TITANIUM ALLOY

Abstract— Fatigue thresholds and crack growth rates were studied in the experimental alloy, Ti—5Al—4Mo, as a function of temperature, grain size and hydrogen concentration. Deformation is confined to planar slip bands along which fracture occurred at low hydrogen concentrations. Hydrogen accelerated crack growth rates at various combinations of temperature, grain size and hydrogen with a corresponding change in fracture from "cleavage' to interface phase fracture. In addition, hydrogen was found to promote interface phase formation. It is proposed that stress-assisted hydrogen accumulation increases the interface phase hydrogen concentration which reduces the interface phase fracture stress. This process depends on the local stress and β -phase hydrogen concentrations, temperature and the time under load. At 340 K, hydrogen had a relatively small effect on crack growth due to a change in slip behavior with increased hydrogen concentration.     

A general mixed-mode brittle fracture criterion for cracked materials

In order to predict the fracture direction and fracture loadings of cracked materials under the general mixed-mode state, this paper presents a new general mixed-mode brittle fracture criterion based on the concept of maximum potential energy release rate (MPERR). This criterion can be easily degraded to the pure-mode fracture criterion, and can also be reduced to the commonly accepted fracture criteria for the mixed-mode I/II state. In order to validate the proposed criterion, we have carried out the experiments with aluminium alloy specimens under various mixed-mode loading conditions. The experimental results agree well with the predictions of the proposed criterion.     

Fabrication and actuation of ionic polymer metal composites patterned by combining electroplating with electroless plating

The novel fabrication technique that patterns the multiple electrodes of the ionic polymer metal composite actuators was developed to mimic the swimming and flapping locomotion of a living thing. The developed method is to combine electroplating with the electroless chemical reduction using the patterned mask. The advantages of this fabrication method are that the initial compositing between the polymer and platinum particles can be assured by the chemical reduction method, and the thickness of each electrode can be controlled easily and rapidly by electroplating. By using the fabricated actuator with a multiple degree of freedom, the oscillatory and undulatory waves of the flexible membrane actuator was generated and a twisting motion was also realized to verify the possibility of mimicking the fish-like locomotion. Present results show that this novel method combining electroplating with electroless plating can be a promising technique to easily pattern multiple electrodes and to implement the biomimetic motion of the polymer actuators with good mechanical bending performance.     

减震器托架断裂失效分析

目的解决减震器托架断裂失效的问题。方法通过化学成分分析、力学性能分析、断口扫描分析、金相组织分析、氢含量测试等手段,确定了减震器托架断裂性质及原因。结果减震器托架发生氢脆断裂。结论由于酸洗过程中材料渗入过量氢,导致氢脆并发生断裂。为防止类似的失效事故再次发生,提供了一些指导性建议。     

不对称交流-直流电镀Fe-纳米ZrO2复合镀层工艺的研究

为提高镀铁层的硬度及耐磨性能,采用氯化物低温镀铁工艺,选择纳米ZrO2作为第二相粒子,以不对称交流-直流电源电镀法制备了Fe-纳米ZrO2复合镀层.研究了不对称交流-直流镀铁工艺对镀层的影响,考察了工艺参数对镀层中ZrO2复合量的影响以及表面活性剂对镀层性能的影响.结果表明,采用不对称交流-直流电镀方法可获得内应力小、光滑致密的复合镀层,有效降低镀层裂纹的产生;通过控制工艺参数可调节镀层中ZrO2纳米粒子的复合量;在镀液中加入阴离子型表面活性剂十二烷基硫酸钠可降低纳米粒子的团聚,获得最佳的镀层综合性能.     

High Aspect Ratio Microcolumns to Manipulate Single Electrons on a Liquid Helium Surface for Quantum Logic Bits

Electrons are bound to the surface of liquid helium by the image potential due to the induced polarization of the helium. The potential varies as the reciprocal of the distance of the electron from the surface so that the energy levels for the electron motion perpendicular to the surface are those of a one-dimensional hydrogen atom with very small charge. In order to make quantum logic elements (qubits) using the ground state and first excited state in this potential, individual electrons must be confined over microelectrodes which are individually connected to variable voltage sources so that the electron energy levels can be shifted in and out of resonance with applied microwave radiation. The electrodes consist of an array of gold columns, about 1.2$muhbox m$tall and 200 nm in diameter, separated by 500 nm. These are grown by electroplating on the ends of leads deposited on a silicon substrate by e-beam lithography. The leads are covered by a dielectric layer and then a metal ground plane, so that the electric field from the leads is screened. We describe, here, our technique for fabricating this system and present the numerical computations of the electric fields from the electrodes.     

Hydrogen induced rupture of Ni 201 discs

Abstract

The hydrogen embrittlement of Ni 201 has been investigated by pressurizing small thin discs from one side with gaseous hydrogen. The time to rupture was found to increase with decreasing pressure. The lowest rupture pressures were achieved after times about equal to the time required for penetration of the discs by lattice diffusion of hydrogen. It was therefore concluded that dislocation transport was not very significant in this particular system. Discs ruptured with air failed by chisel point fracture. Discs ruptured with hydrogen showed increasing amounts of intergranular fracture with increasing time of exposure. Intergranular fracture was predominant near the surface exposed to hydrogen.

MST/454     

Finite Element Analysis of Hydrogen Transport in Steel Pressure Vessel at Room Temperature

Hydrogen embrittlement is commonly considered as an important failure mechanism for steel pressure vessels and pipes made of such as Cr–Mo and 4130X steels under high-pressure hydrogen environments, which means hydrogen atom can easily penetrate and diffuse into the metal, leading to the distortion of microscopic lattice and the degradation of macroscopic strength and fracture toughness. Under the support of the National Key Fundamental Research and Development Project of China (2015.1-2019.12), we aim to launch a series of theoretical, experimental, and numerical research on the macroscopic damage evolution and microscopic fracture of steel structures under high-pressure hydrogen environment, which ultimately commits to gaining deep insight into the hydrogen embrittlement mechanisms. This work studies the hydrogen transport mechanisms in Cr–Mo steel pressure vessels under different hydrogen environments using finite element analysis (FEA), which is fundamental to subsequent research on the hydrogen-induced damage evolution and crack behaviors. The purpose of this paper is to explore the effects of the initial hydrogen concentrations and structural sizes on the hydrogen transport mechanisms in 2.25Cr-1Mo pressure vessels with a nozzle at room temperature. Numerical results by comparing different hydrogen concentration distributions show that structural discontinuities tend to accelerate the hydrogen embrittlement sensitivity.     

实用断裂试验方法的意义与内容（一）

为了在材料性能检测中普遍、持久地应用断裂试验，推荐一种延性材料断裂韧性实用测试方法。该实用测试方法包括侧切三点弯曲试件、测量δｃ的两点位移法和测量ＪＩＣ的位称计法。该方法具有科学合理、通谷易懂、准确可靠、简便快捷、费用低廉等显著特点，适合普遍推广应用。     

65Mn钢弹簧垫圈开裂原因分析

通过宏观检验、化学成分分析、硬度测试、金相检验和断口分析等方法对65Mn钢弹簧垫圈的开裂原因进行了分析。结果表明:该垫圈氢含量较高,服役时大部分区域处于悬空状态,造成垫圈变形不均匀,形成应力集中。另外,垫圈凸面的防滑压花以及压花边缘的轮廓线处也存在应力集中,氢原子容易在此聚集,最终导致垫圈发生了氢致延迟脆性开裂。     

Mechanism of resistance degradation of lead magnesium Niobate-based ferroelectrics induced by hydrogen reduction during electroplating

Resistive leakage of lead magnesium niobate (PMN) based relaxor ferroelectrics after nickel electroplating was investigated through X-ray photoelectronic spectroscopy (XPS) analysis and annealing experiments in oxygen and argon. It was found that the resistivity of the ceramics declined nonlinearly with the electroplating time. XPS analysis suggested that the reduction of Nb⁵⁺ to Nb⁴⁺ by hydrogen during electroplating played an important role in the degradation. It was also noted that the degraded specimen can recover its properties completely after oxygen annealing at 600°C for 1 hour through the oxidation of Nb⁴⁺ to Nb⁵⁺. In contrast, almost no oxidization of Nb⁴⁺ and improvement of the degradation were observed for the degraded specimen after argon annealing. Therefore, it was concluded that the resistance degradation of the PMN-based relaxor ferroelectrics during electroplating must be ascribed to the oxygen loss and the reduction of Nb⁵⁺ to Nb⁴⁺.     

Sn40Pb共晶合金电镀工艺

目的对Sn40Pb共晶合金电镀工艺过程进行研究。方法采用电镀和超声辅助搅拌,Sn40Pb作为电镀阳极,在铜片上成功的制备了Sn40Pb共晶合金镀层。结果研究表明随着电流密度增大,镀层厚度增加,镀层中铅含量增加较快,电流密度过大时阴极析氢反应剧烈,锡铅镀层会变得粗糙,致密性变差。结论当电镀液成分为甲基磺酸为12 m L(24 g/L)、甲基磺酸锡为8 m L(16 g/L)、甲基磺酸铅为3.7 m L时,控制电流密度在4 A/dm~2、电镀时间为5 min左右,可以获得接近锡铅共晶的理想合金镀层。