Microstructure and Corrosion Behavior of Electrodeposited Ni-Co-ZrC Coatings

In this present work, ZrC particles incorporated Ni-Co composite coatings were electrodeposited. The objective of this article is to study the influence of Co content on the microstructure and properties of Ni-Co-ZrC coatings. Pure Ni and Ni-ZrC coatings have also been electrodeposited for comparison. Surface morphology, chemical composition, microstructure, and microhardness of Ni-Co-ZrC coatings were characterized by scanning electron microscopy, energy dispersive spectrometer, x-ray diffractometer, and Vicker microhardness tester. The potentiodynamic polarization technique was applied to measure the corrosion behavior of the coatings. By increasing Co concentration in electrolyte, Co content of the coatings was modified from 0 to 80 wt.% and ZrC particles content of the coatings was reduced. As the Co content increased, the dominant phase structure was changed from face centered cubic to hexagonal close packed crystal structure. Surface morphology of the Ni-Co-ZrC coatings was changed from nodular to sharp corner structure, and finally branched morphology with increasing Co content of the coating. Among the electrodeposited coatings, Ni-Co-ZrC coating with 42 wt.% Co content exhibited the highest microhardness. The corrosion potential of the coating was shifted to more positive with increasing the Co content from 0 to 64 wt.%. The lowest corrosion rate of 4.507 × 10^?7 g·h^?1·cm^?2 was found for Ni-Co-ZrC coating at the Co content of 75 wt.%.     

Microstructure and Corrosion Resistance of Electrodeposited Ni-Cu-Mo Alloy Coatings

This paper deals with the electrodeposition of Ni-Cu-Mo ternary alloy coatings on low-carbon steel substrate from an aqueous citrate sulfate bath. The structures and microstructure of coatings were characterized by scanning electron microscopy and x-ray diffractometry. The corrosion resistance of coatings was investigated by potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy techniques. The results show that the Ni-Cu-Mo coatings are mainly composed of fcc-Ni phase and a small amount of NiCu phase. Ni-Cu-Mo coatings exhibit a nodular surface morphology, and the roughness of electroplated coating increases with the increasing of Na₂MoO₄·2H₂O in the bath. The corrosion performance of the coatings is significantly affected by the Mo content of the alloy coating and their surface morphology. The coating prepared in bath containing 40 g/L Na₂MoO₄·2H₂O has the highest corrosion resistance in 3.5 wt.% NaCl solution, while that prepared in bath containing 60 g/L (or more) Na₂MoO₄·2H₂O shows a lower corrosion resistance due to the presence of microcracks on the coating surface.     

钨丝-镍复合电铸新技术

提出一种新的纤维-金属复合电铸层——钨丝-镍复合电铸层的电铸技术,研究脉冲电流、钨丝体积分数等对复合电铸层常温和中温拉伸性能的影响。结果表明：常温下,随着高强度钨丝的不断掺入,复合电铸层的拉伸强度不断提高,当钨丝的体积分数达到45%时,拉伸强度达到峰值1 650 MPa;脉冲电流的应用能够显著细化镍晶粒,降低复合电铸层内部孔隙率,获得的钨丝-镍复合电铸层拉伸强度比使用普通直流的拉伸强度提高了30%左右;在200、400和600 ℃的中温条件下,钨丝-镍复合电铸层依然具有很高的拉伸强度,但是随着温度的继续升高,拉伸强度迅速降低。     

激光重熔喷射电沉积纳米晶镍涂层微观结构

采用喷射电沉积法在45钢基体表面制备了纳米晶镍涂层,研究了激光重熔工艺对组织的影响.用扫描电镜、X射线衍射仪和显微硬度计分析了涂层表面形貌、微观结构和显微硬度.结果表明,在优化的工艺参数下,喷射电沉积制备的镍涂层表面较平整、结合较致密,由平均尺寸为13.7 nm的纳米晶颗粒组成,但晶粒间仍有一定的间隙;经激光重熔后,熔融区内的晶粒尺寸明显减小,使涂层致密化程度得以提高并使涂层与基体由机械结合变为冶金结合,因此激光重熔处理后涂层的显微硬度明显提高.     

脉冲复合镀层Ni-W-P-SiC和RE-Ni-W-P-SiC的组织与相结构分析

运用X射线衍射仪、电子探针X射线能谱仪等手段分析研究了Ni-W-P-SiC和RE-Ni-W-P-SiC脉冲复合镀层的组织结构.结果表明,Ni-W-P-SiC和RE-Ni-W-P-SiC两种脉冲复合镀层表面比相应直流镀层光滑平整细腻得多,脉冲参数不同会得到表面平整程度和粒度不同的镀层,稀土的加入使RE-Ni-W-P-SiC复合镀层比Ni-W-P-SiC复合镀层晶粒更细小、截面更均匀;同时热处理温度和时间对镀层的截面形貌也有影响,Ni-W-P-SiC、RE-Ni-W-P-SiC脉冲镀层在镀态时都是非晶态结构,随着热处理温度的升高,两脉冲复合镀层的非晶态形态逐渐减弱,镀层逐渐向晶态转变,Ni3P相的衍射峰逐渐加强,且不断出现新相的特征峰;稀土元素的加入对脉冲镀层在镀态和热处理时相结构有一定程度影响.     

含稀土镀液电沉积镍镀层耐蚀性的研究

借用扫描电镜、电化学分析和腐蚀失重实验方法研究了镀液中添加RE经直流和单向脉冲电沉积方法制备的镍镀层的耐蚀性。结果表明：单向脉冲法制备的镍镀层抗腐蚀能力优于直流法制备的镍镀层抗腐蚀能力，其原因主要归于单向脉冲镀层结晶比较细小致密，直流镀层结晶较粗大且致密性差。     

电沉积FeNi合金电磁屏蔽性能研究

采用电沉积工艺在铜基体上得到了Fe21Ni79铁镍合金,通过XRD确定了电沉积铁镍合金的晶体结构,通过扫描电镜观察电沉积铁镍合金的表面形貌.运用低频磁场源和交变磁强计自制低频电磁屏蔽效能测试平台测量复合材料在0～1900Hz电磁屏蔽性能,运用Aligent信号源和矢量网络分析仪测量100 kHz～1.5 GHz电磁屏蔽...     

Studies on High Temperature Oxidation of Electrodeposited RE-Ni-W-P-SiC Composite Materials

WITH the rapid development of modern industries theproducts in engineering industry were continuallychallenged by the requirements of long-term and stableworking at higher temperature,pressure,speed andunder adverse conditions.Consequently,the surfaceproperties of the products,such as the resistance tooxidation at high temperature,the resistance to wearand the resistance to corrosion,should be improvedcontinually.Although the equipment or parts made outof expensive metals or alloys wholly can…     

Effects of Diffusion from Brass Substrates into Electrodeposited Tin Coatings on Corrosion Resistance and Whisker Growth

Tin coatings electrodeposited direct on brass have an initial trace zinc content which makes them liable to tarnish in atmospheres containing sulphur dioxide. When more zinc reaches the surface by diffusion from the substrate, susceptibility to corrosive agents increases. Undercoats of copper or nickel are effective long-lasting barriers to zinc diffusion but permit the slower and less damaging growth of intermetallic compounds. Increased thickness of tin coating delays the arrival of diffusing metal at the surface and also reduces the effect on solderability of corrosion of a diffused coating. Diffusion is faster in tin coatings deposited bright. Tests to assess the extent of zinc diffusion and the liability of a coating to deteriorate in long storage with corrosion risk are discussed. Susceptibility of tin coatings to whisker growth has some parallel with their tendency to interdiffuse with the substrate.     

超声波对电沉积Ni-Al_2O_3复合镀层耐磨性的影响

采用超声-电沉积方式制备Ni—Al2O3复合镀层。利用X-射线衍射仪、扫描电子显微镜、硬度仪以及摩擦磨损实验仪对复合镀层的组织结构、宏观残余应力、表面形貌、微观硬度以及摩擦磨损性能等进行研究。实验结果表明：适当的超声波作用使复合镀层基质金属Ni的晶粒细化,复合镀层的硬度提高,但也相应地增加了镀层的宏观残余应力;超声波-电沉积复合镀层的表面致密平整,镀层中粒子团聚现象减少,粒子分布更加均匀;超声-电沉积复合镀层的耐磨性明显优于单独电沉积复合镀层。     

电铸制备TiB_2/Cu复合材料的性能

使用粒度约为3μm的导电陶瓷TiB_2颗粒作为铜基复合材料的增强相,在酸性硫酸铜溶液中用电铸方法制备TiB_2/Cu电火花加工用工具电极。用扫描电镜和金相显微镜观察其组织结构,用维氏硬度计测量硬度,用中性盐雾试验测量其耐腐蚀性,用电火花加工脆硬材料衡量其抗电蚀性。结果表明:电铸Cu与TiB_2/Cu晶粒平均直径分别为30,10μm,硬度分别为984,1235 MPa,腐蚀失重分别为47.8,40.3 mg;TiB_2颗粒的加入可显著细化晶粒,提高硬度、耐腐蚀性和抗电蚀性。     

铝合金基电沉积Ni-SiC复合镀层的结构及耐蚀性研究

利用SEM观察了Ni-SiC复合镀层的表面形貌结构 ,同时利用电化学方法对铝合金表面电沉积Ni-SiC复合镀层的耐蚀性能进行了研究。结果表明 ,Ni-SiC复合镀层的表面形貌与纯Ni镀层截然不同 ,耐蚀性能优于纯Ni镀层 ,经过 3 0 0℃× 2h热处理后 ,耐蚀性能进一步得到提高     

Size Effect of Al Particles on the Oxidation of Electrodeposited Ni–Al Composite Coatings

Electrodeposited microparticle-dispersed composite coatings (EMCCs) and nanoparticle-dispersed composite coatings (ENCCs) of Ni–Al were developed by co-electrodeposition of Ni with various contents of Al particles. The Al microparticles were in a size range of 1 ~ 5μm, and the Al nanoparticles had an average size of 75 nm. TEM characterization showed that compared to EMCC, ENCC exhibited a more-homogeneous distribution of particles, a greatly narrowed interparticle spacing, and finer Ni grains. The oxidation performance at 950°C of the as-deposited composite coatings depended not only on the aluminum content but also on the particle size, which was concluded from two observations: (1) for a given Al content, the oxidation resistance of the ENCC was better than that of the EMCC counterpart; (2) the content for the formation of a continuous alumina layer on the ENCC was significantly reduced compared to the EMCC. Codeposition of the nanoscale Al particles instead of the micrometer-sized counterparts led to a great increase of the number per unit volume of the Al particles available for alumina nucleation, which favored the ENCC Ni–Al to thermally grow alumina scales during a short transient stage of oxidation. A mechanism is proposed to interpret the particle size effect on the transient oxidation.     

Selective Dissolution of Electrodeposited Zn-Ni Alloy Coatings

The corrosion of Zn-Ni alloy coatings in pure and NaHCO, containing Nad solutions was investigated under open circuit potential conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques were applied for the alloy surface characterisation, while direct current plasma emission spectrometry was used for test solution and corrosion product film analysis. It has been established that Zn dissolves preferentially leaving a top layer slightly enriched with Ni. However, this layer does not act as a barrier layer for the further corrosion attack. The presence of NaHCO₃, in NaC! solution causes a reduction in the corrosion rales of Zn-Ni alloy and the thickness of corrosion product (oxide) film, as well as affecting the ratio of the soluble and insoluble fractions of ionised Zn and Ni and the development of the surface morphology. In a pure NaCl solution Zn-Ni corrosion occurred with surface roughening, while in the presence of NaHCO₃ the process was accompanied by surface smoothing.     

Synthesis and Characterization of Electrodeposited Nanocrystalline Nickel

NANOCRYSTALLINE materials exhibit ultra-highstrength,superior wear resistance and enhancedsuperplastic formability compared with theirconventional coarse-grained counterparts ll~31.As aresult,there has been a great emphasis on studyingthese materials.And the synthesis of nanocrystallinemetals and alloys is a particularly important topic.Many synthesis techniques for production ofnanocrystalline materials have been developed,such asinert gas condensation,ball milling,sol-gel technique,spu…     

Plasma Spray Coatings of Ni-Al-SiC Composite

Ni-Al-SiC powder mixture containing 12 wt.% SiC was prepared by conventional ball milling. Morphological and microstructural investigations showed that powder particles after 15 h of milling time had the optimum characteristics with respect to their size and microstructure. X-ray diffraction patterns of powder particles included only the elemental Ni, Al, and SiC peaks without any traces of oxides or intermetallic phases. The powder mixture was then deposited onto a steel substrate by atmospheric plasma spray (APS) process under different conditions. The results showed that under APS conditions used here, the coatings were composed of various intermetallics including Ni-Al and Ni₂Al₃. The mean hardness of coating was found to be about 567 HV. It was also found that by increasing current density of APS, the coating/substrate adhesive strength was increased.     

Electrodeposited composite tin-lead coatings

The structures, morphologies and composition of tin-lead alloy electrodeposits, with and without dispersed silicon carbide particles, were studied using a rotating cathode. The incorporation of silicon carbide particles was found to reduce the rate of reduction of tin ions.     

辅助磨擦对镍电铸层力学性能的影响

在磨擦辅助电铸镍过程中,通过改变游离微珠对电铸层表面的磨擦强弱,制备不同力学性能的镍电铸层。对所制备镍电铸层的表面形貌、织构等微观结构和显微硬度、抗拉强度及伸长率等性能进行测试和分析。结果表明：采用卧式放置的阴极能制得材料组织结构均匀的电铸层。且随着阴极表面线速度的提高,游离微珠对电铸层的整平作用和晶粒细化作用增强。在不同线速度下采用旋转阴极可以制备大范围力学性能的镍电铸层,其表面粗糙度为0.15~0.03 μm、硬度为185~410HV、抗拉强度为525~1 020 MPa、伸长率为24%~4%。     

电沉积Fe-Cr-Ni合金的电化学腐蚀行为

以硫酸盐为主盐,研究了工艺参数中温度、电流密度对Fe-Cr-Ni镀层沉积速率和腐蚀性能的影响。采用电化学试验方法研究不同条件下所获得的镀层在NaCl溶液中的腐蚀行为,结果表明,在饱和NaCl溶液中镀层都有钝化性能。60℃下获得的镀层有明显过钝化现象,抗腐蚀性能较差。不同电流密度下的镀层显示了不同的电化学性能。电流密度为5 A/dm2时,处于钝态时,电流随着电位的正移逐渐增大是一个非常缓慢的过程,钝化膜仍然发挥作用。在饱和NaCl溶液中,电流密度为5 A/dm2时所获得的镀层的耐蚀性能较好。     

电沉积镀镍层的无铬钝化工艺

采用正交试验法筛选了一种以植酸、钼酸钠和缓蚀添加剂为基本组成的无铬钝化液。通过电化学阻抗谱测试,确定了最佳成膜时间;通过5％CusO4。点滴试验、10％NaCl浸泡试验和极化曲线测试,对电沉积镀镍层无铬钝化后的耐蚀性能进行了研究。结果表明,采用本无铬钝化工艺后,镀镍层耐蚀性能良好。