电流密度和施镀温度对铝合金表面Ni-SiC-MoS2复合镀层显微组织的影响

目的研究电镀工艺参数中的电流密度和施镀温度对铝合金表面Ni-Si C-MoS_2复合镀层组织形貌及成分的影响。方法利用复合电镀的方法在铝合金上制备Ni-Si C-MoS_2复合镀层。通过扫描电子显微镜、能谱仪以及显微硬度仪,分析不同电流密度和施镀温度下复合镀层的组织结构、成分、界面之间的结合情况以及显微硬度。结果电流密度为4 A/dm2时,镀层与基体的结合差,镀层表面粗糙不平;当电流密度增加到5 A/dm2时,镀层与基体结合紧密,并且镀层表面平整;当电流密度增大到6 A/dm2时,镀层表面平整度变差。施镀温度为40℃时,镀层厚度较薄;施镀温度为50℃时,镀层与基体结合良好,镀层表面平整;当施镀温度上升到60℃时,镀层与基体结合处出现裂纹,镀层质量下降。随电流密度和施镀温度的升高,镀层中Si C和MoS_2摩尔分数先增加后减小,显微硬度先增大后减小。结论采用复合电镀的方法在铝合金表面可以制备出Ni-Si C-MoS_2复合镀层,当电流密度为5 A/dm2、施镀温度为50℃时,制备出的Ni-Si C-MoS_2复合镀层表面平整,厚度均匀,Si C与MoS_2摩尔分数可分别达到10.40%和0.77%。复合镀层的显微硬度与其Si C含量成正比,最高可达357.7HV0.01,是基体合金硬度的3.7倍。     

Ni-SiC纳米复合镀工艺及性能研究

 在纯铜板上制备了含有纳米SiC的镍基复合镀层，利用扫描电镜观察镀层表面显微组织.研究了含量、阴极电流密度、pH值、温度、时间、搅拌等主要工艺参数对纳米SiC在复合电沉积中沉积量的影响.并用MM-200磨损试验机检测了所得复合镀层的耐磨性能.X-ray衍射证明镀层中存在纳米SiC粉末；纳米SiC镍基复合镀层成型工艺参数为：电流密度3 A/dm2～15 A/dm2，温度30℃～60℃，pH值3～4，超声波辅助慢速机械搅拌；最佳含量40 g/L；纳米Ni-SiC复合镀层的耐磨性能优于纳米Ni-Al2O3复合镀层及纯Cr镀层.       

硫代硫酸盐无氰镀银工艺及银镀层微观组织分析

采用硫代硫酸盐无氰镀银工艺,分别以 AgNO3和 AgBr 为主盐进行镀银。研究主盐含量、电流密度对Ag镀层表面质量、沉积速率和显微硬度的影响,并优化电镀参数。分析优化工艺下的Ag镀层结合强度和晶粒尺寸。结果表明：在AgNO3体系中,AgNO3最佳用量为40 g/L,最佳电流密度为0.25 A/dm2,制备的Ag镀层光亮平整,与基体结合良好,晶粒尺寸为35 nm。在AgBr体系中的最佳AgBr用量为30 g/L,最佳电流密度为0.20 A/dm2,与基体结合良好的Ag镀层的晶粒尺寸为55 nm。与AgBr体系相比,AgNO3体系适用的电镀电流密度范围较宽,制备的Ag镀层显微硬度高,晶粒尺寸小。     

电沉积法制备Ni-Ti3SiC2复合镀层

以自制纯度超过98%(体积分数,下同)的Ti3SiC2陶瓷粉体为原料,加入分散剂和表面改性剂,制成稳定悬浮液,并加入Watts镀镍电镀液,利用磁力搅拌分散均匀,在阴极电流密度2 A/dm2～5 A/dm2下,在低碳钢基体表面成功得到Ni-Ti3SiC2减摩复合镀层.SEM观察表明,表面改性剂的加入有效地改变了粉体表面电导性质,得到致密平整的复合镀层结构.XRD及EDS分析表明:镀层中Ti3SiC2微粒含量为5%～14%(体积分数,下同).当制备过程中以间歇式搅拌代替连续搅拌时,可得到Ti3SiC2相含量超过30%的复合镀层.复合镀层的显微硬度随微粒含量的升高而增大.     

工艺参数及稳定剂抗坏血酸对电沉积NiFeW合金的影响

为获得性能良好的镍铁钨合金镀层,研究了镀液pH 值、温度、电流密度、稳定剂抗坏血酸浓度对镍铁钨合金镀层成分和镀层沉积速率、显微硬度的影响。结果表明: 镀液pH 值对镀层W含量和镀层沉积速率影响较大;镀液温度对镀层沉积速率、镀层成分和镀层硬度影响均较大;随抗坏血酸浓度增加,镀层沉积速率逐渐降低,镀层表面形貌更加粗糙。在镀液pH = 4,温度60 ℃,电流密度4 A/dm2,抗坏血酸浓度3 g /L 时,镀层沉积速率和镀层的显微硬度较高,表面光亮致密,耐蚀性好。     

S135钻杆钢表面Fe-Ni-W合金镀工艺

利用正交试验,选择温度、主盐浓度等4个因素,通过极差分析,确定了S135钻杆钢电沉积Fe-Ni-W合金镀层的最佳制备工艺,研究了镀液pH值、电流密度以及柠檬酸钠对镀层的组分、显微硬度和沉积速率的影响。结果表明：在本试验的制备条件下,获得的合金镀层结构为非晶态;随着镀液PH升高,镀层显微硬度先增大后减小,沉积速率总体呈下降趋势;镀层沉积速率随电流密度增加也逐渐增大,当电流密度从6 A/dm2增大到15 A/dm2时,合金硬度增加趋势较大,从320 HV到540 HV;当增加镀液中的柠檬酸钠含量,铁和钨均呈现增加趋势,而镍含量却出现下降趋势,同时,镀层硬度先增大后减小,沉积速率逐渐减小。     

电沉积方式对Cu-nanoAl_2O_3复合镀层组织结构和显微硬度的影响

用直流和单脉冲电镀法制备了Cu-nanoAl2O3复合镀层。通过扫描电镜观察了镀层的表面形貌,用X射线衍射仪分析了镀层的微观晶体结构,分别研究了影响直流和单脉冲纳米复合镀层显微硬度的各种因素。结果表明,与直流电镀方法相比,脉冲电镀方法使镀层晶粒尺寸变小,在T=24℃,Al2O3、粒子添加量25g/L、搅拌速度240r/min、阴极平均电流密度4A/dm2条件下,直流电沉积Cu-nanoAl2O3复合镀层硬度最大,在直流电镀工艺条件基础上选择频率为200Hz、工作比为0.3的单脉冲工艺条件制备的复合镀层硬度最大。     

搅拌速度对铝合金表面电镀Ni-SiC的影响

主要以硫酸镍、氯化镍、磷酸和碳化硅为基本组分的镀液,通过采用电镀法在铝合金基体上获得Ni-SiC复合镀层,着重探讨搅拌速度对铝合金表面电镀Ni-SiC的影响,并得出最佳的搅拌速度.结果表明:搅拌速度对镀层性能有很大影响,当搅拌速度为300r/min时,镀速最大,而且镀层均匀、紧凑、细小,耐腐蚀性能良好,镀层中SiC含量也达到最大.     

电流密度对柔性摩擦辅助电沉积镍镀层质量的影响

为提高镀层沉积速度和沉积质量,采用新型的柔性摩擦辅助电沉积技术在不同的电流密度下制备了镍镀层。利用SEM、XRD、X射线应力衍射仪以及硬度计等手段对镍镀层的组织结构和性能进行了表征。结果表明:电流密度对柔性摩擦辅助电沉积镍镀层的质量具有重要影响。在1~13 A/dm2的电流密度范围内,随着电流密度的增大,柔性介质的摩擦整平作用逐渐减弱,镀层的择优取向发生了(111)晶面向(200)晶面的过渡转变;当电流密度达到13 A/dm2时,镍镀层出现了(200)和(220)晶面的双择优取向,但择优取向程度不大;电流密度为10 A/dm2时,柔性摩擦辅助电沉积镍镀层具有最低的拉应力,为150 MPa左右,最小的表面粗糙度为Ra=0.48μm,最小的孔隙率为0.08 cm-2,最高的硬度为385 HV。     

Preparation of Ni-SiC Composite Coating by Electrochemical Deposition

采用电化学沉积法通过在电解槽中添加SiC颗粒制备Ni-SiC复合镀层。由于第二相颗粒SiC的加入改善了镀层的性能,使之具有高硬度、耐磨性和耐腐蚀性能等。Ni-SiC复合电镀改善镀层的组织结构并显著提高镀层的质量。采用NiSO4·6H2O（35 g/100 mL）,NiCl2·6H2O（4 g/100 mL）,H3BO3（3.5 g/100 mL）,十二烷基硫酸钠（0.5 g/100 mL）,SiC颗粒（0.4~1.0 g/100 mL）体系,在pH值为4,温度35~50 ℃时,通过电化学沉积法制备Ni-SiC复合镀层。实验探究了温度、电流密度、镀液中碳化硅颗粒含量以及超声波分散时间对镀层中SiC复合量的影响。通过扫描电镜和XRD对镀层进行分析,结果表明：在温度为35~50 ℃之间复合镀层中SiC的量随温度的增加呈现先增加后减少的趋势;在电流密度为0.026~0.06 A/cm2之间,复合镀层中SiC的含量随电流密度的增加呈现先增加后减小的趋势;镀液中SiC量在0.4~1.0 g/100 mL之间时,镀层中SiC含量随着镀液中SiC含量的增加而增加,超过一定值（0.6 g/100 mL）增加幅度变小;超声波分散时间在10~50 min之间, 镀层中SiC的含量随时间的增加而先增加后减少。镀层中碳化硅颗粒均匀分布有利于晶粒的细化     

Plating in a barrel,how does it work? A Study of Local Mass Transfer and Current Density Distribution in a Barrel

The barrel plating study we have made has two different aspects. The first one describes the solution transfer from the tank to the barrel and how it manages to reach the parts. The main parameters that influence the solution distribution have been pointed out. The relative movement of the parts and the relative movement of the solution have been studied. Some laboratory prepared solutions simulating industrial electrolytes let us quantify these movements. Optical methods allow us to break down the relative motion in different representative static positions.

The second aspect studies the current density and the diffusion limiting current density distribution. The current density distribution has been studied during representative static electrolysis with solution motion. It has also been evaluated via measurements of local galvanic potential in the barrel. Tracer methods have been used to measure the diffusion limiting current density.

Through these two aspects, we have begun to develop a model to describe both these distributions and to correlate them with the external parameters of the plating (current, properties of the electrolyte, speed of rotation, shape of the barrel,…). It has led us to improve the correlation between the current density and the mass transfer distributions.     

The Effect of Current Surging on the Electrodeposition of Microcracked Chromium

The influence on the microcracking of chromium of raising the plating current density from a base level to a higher or surge level at a controlled frequency has been investigated. Optimum values of the respective current densities, as well as the proportion of time occupied by surging, have been established in both laboratory and pilot-scale tests. The results indicate that the plating time required to develop a uniform microcrack pattern under steady current conditions is reduced substantially by the application of current surging. A tentative explanation of the observations is advanced based on a comparison of the relative effects of an unsurged current density on chromium thickness and crack pattern.     

Einfluß von Molybdän und Aushärtungsgrad auf die Korrosionseigenschaften chromlegierter martensitaushärtender Stähle

Influence of molybdenum and degree of hardening on the corrosion properties of chromium alloyed maraging steels The influence of intermetallic precipitations on the corrosion resistance of maraging chromium alloyed steels with various molybdenum contents has been studied by tracing potentiokinetic and potentiostatic current density/potential curves. It has been shown that the passivation current density and the passive current density are measures of the corrosion resistance. Hardening times yielding maximum strength result in an increased dissolution current density; in this context increased molybdenum contents displace the increase of the current density toward longer times. Corrosion tests in artificial seawater distinctly show the positive influence of molybdenum which displaces the rapture potential toward more nobel values.     

Fabrication of microprism mould by electroforming with high electrolyte flowrate

Abstract

Electroforming is applied to fabricate microprism moulds, however only low working current density is employed because the higher current density at the edge limits the usable value of the working current density. Reduction of current density at the edge is a key in the enhancement of the working current density. In this paper, a secondary cathode was introduced to lower the edge current density. By this technique, the edge current density of the primary cathode surface is not only weakened obviously but can be even lower than that of the others. In addition, a high electrolyte flow rate has been introduced to improve working current density. Experimental results show that both the microhardness and tensile strength of the electroformed layer increase with electrolyte flowrate. By using both secondary cathode and high speed electrolyte flow, the electroforming time could be reduced significantly and mechanical properties of the electroformed layer are not adversely affected in electroforming of microprism moulds.     

处理电流密度对钴基非晶薄带巨磁阻抗效应的影响

本文研究了焦耳处理工艺的处理电流密度对Co68.15Fe4.35Si12.5B15和Co71．8Fe4．9Nb0.8Si7．5B15非晶薄带巨磁阻抗效应的影响。样品在不同电流密度下进行了处理。实验结果表明：焦耳处理存在最佳电流密度,对Co68.15Fe4.35Si12.5B15窄带来说,最佳处理电流密度为30A／mm^2,处理后样品的阻抗变化率峰值和灵敏度分别为119％和73％／Oe;对Co71．8Fe4．9Nb0.8Si7．5B15窄带来说,最佳处理电流密度为35A／mm^2,处理后的阻抗变化率峰值为232％,灵敏度在30A／mm^2时达到42％／Oe。处理后样品的内应力得到有效释放,软磁性能提高,使薄带的巨磁阻抗效应较淬态时有了明显提高。处理电流密度是焦耳处理方法中影响钴基非晶薄带巨磁阻抗效应的一个重要参数。     

Determination of electrochemical corrosion parameters using discrete Laplace transformation

Abstract

Discrete Laplace transformation has been used to determine the corrosion current and Tafel slopes from experimental data. The approach is based on thefact that the Wagner– Traud equation, relating the measured current density to the overpotential, can be expressed as a convolution of two functions. One of these functions is dependent on a single Tafel slope only, thus making the determination of the other Tafel slope and current density easier. This method has been assessed using hypothetical datafor a variety of systems. The effect of experimental inaccuracies has been checked by introducing random errors into the otherwise exact hypothetical data. It was found that the method gives very rapid convergence towards the solution even when the data contain a degree of inaccuracy. The present method can easily handle situations where other known methods fail to converge.     

The effect of growth rate on anodically formed zirconium oxide films

Anodic oxide films have been grown on zirconium at constant current densities for a range of current densities extending over several orders of magnitude. Optical and scanning electron microscopy have shown structural differences for different current densities and the mechanical failure of the films has been studied by tensile testing after oxidation. As the current density was reduced, blistering and breaking of the oxide layer was found to increase and this has been associated with anomalies in the experimental voltage-time graphs. The relationship between electric field in the oxide and the current density has been investigated and values of the activation energies of diffusion have been estimated for both oxygen ions and zirconium ions. Possible mechanisms are discussed for the stress relaxation found to occur increasingly for current densities from 0·01 to 1 mAcm^?2.     

The remarkable passivity of austenitic stainless steel in sulphuric acid solution and the effect of repetitive temperature cycling

The passivation of 316L austenitic stainless steel in sulphuric acid solution has been measured at a single temperature, and then further, after a series of temperature sweeps. After 15 h at 20 °C and constant electrode potential, the passive current density has fallen to 16 nA cm⁻² and still continues to decline, with no evidence of an approach to the steady state. After subjecting the metal to a series of temperature sweeps the passive current density has decayed much further to ca. 0.5 nA cm⁻² and probably still decaying slowly. The metal is thereby rendered extremely passive. It is argued that the passive current density as measured by conventional potential sweep voltammetry is not in fact the steady state current density, because the true approach to a steady state is far too slow.     

Study on traveling magnetic field casting of sheet components

The distribution of a magnetic field over an inductor used for sheet castings has been investigated experimentally. With an increase in height from the surface, the magnetic field density decreases according to the exponential law. In the transverse direction, the magnetic field density is approximately uniform except near the edges. The magnetic field density is direct proportional to the number of turns multiplied by the current in amperes. Ferromagnetic material in the upper mould can enhance the magnetic field density. Under the electromagnetic force, the mould-filling process of sheet casings has been studied by physical simulation method. The difference in filling capability between gravity casting and travelling magnetic field casting has been studied. The electromagnetic force can enhance the filling process, but it also brings a problem. With an increase in the magnetic field density, the surface quality of the aluminum alloy sheet castings becomes poor. The reason is discussed.     

The Dyeing of Anodised Aluminium

A solution from which satisfactory deposits can be obtained at considerably higher current densities than are possible with conventional solutions has been developed. Using standardized plating conditions and with fixed concentrations of nickel chloride and boric acid, the concentration of nickel sulphamate has been varied and shown to permit the highest current density at 600 g/1. At 60°C, the maximum current density (400 A/ft²) is nearly twice that of conventional sulphamate solutions under the same conditions. When the temperature is raised to 70°C satisfactory deposits can be obtained at 800 A/ft². The internal stress, hardness and lustre of deposits obtained from the 600 g/1 sulphamate solution operated at pH 4·0, 60°C without addition agents, can be varied as desired by appropriate choice of current density. At the conventional current density of 50 A/ft², hard but ductile deposits are obtained having compressive stress. At the highest current densities, the deposits are softer and the internal stress moderately tensile. Stress-free deposits are obtained at current densities in excess of 200 A/ft². The deposits are lustrous at 50 A/ft² but this lustre diminishes at higher current densities. With the aid of organic addition agents, satisfactory mirror-bright deposits can be obtained at current densities as high as 350 A/ft². The throwing-power of the solution is excellent.