Barrel Plating to Specification

Most barrel plating to-day produces woefully inadequate deposits. This is primarily due to a lack of understanding of the surface area of the load and of the very low current densities which result. Prices commonly quoted for specification plating are lower than the direct cost of the metal which should be deposited. Lack of a reliable method of thickness determination has hidden these facts. Intelligent barrel design, plant layout and process control will help to improve deposit quality and bring barrel plating into line with the product of still vats.     

Hydrogen Embrittlement of Steel by Cathode Charging,Pickling and Cadmium Plating

The effects of electrolytic cathode charging and subsequent ageing at various temperatures on the ductility of mild steel screw wire were investigated and the embrittlement resulting from hydrogen absorption in routine plating operations was studied on slugs cut from such wire and on carbon steel coil springs. Large batches of specimens were processed in the works and representative samples were withdrawn for testing at various stages. The operations considered are pickling, storage in cyanide solution, cadmium plating, hot air centrifuge drying, and baking.

The screw wire slugs were most severely embrittled by pickling and recovered ductility to some extent during plating The springs on the other hand were even more brittle after plating than after pickling; the difference is attributed to the thinner cross-section of the spring wire. The springs show considerably more scatter in plating thickness and there is evidence that the variability of embrittlement is also greater. The slugs show much more consistent results within a barrel load, probably because their shape favours smooth and regular tumbling in the barrel. Differences between batches were only studied with slugs and were found to be much greater than the scatter within a batch.

It is concluded that the scatter and the relative severity of embrittlement induced by different processes depends on the components to be plated.     

Electroplating of Nickel Using a Modified Barrel Design

Nickel is a metal electroplated on a wide variety of articles both ferrous and nonferrous. Small articles which are difficult to jig are frequently plated by barrel plating technique.

In conventional barrel plating the parts to be plated are contacted by either a rod, dangler or metallic wall as they rotate inside the barrel. A modified barrel design has been effected by changing the dangler contact with uniformly distributed contact tips at varying points on the periphery of the barrel. A modification in anode positioning is also made. Improvement in thickness uniformity brought about by use of this modified design are reported in this paper.     

基于离散单元法(DEM)研究镀桶截面形状对机械镀过程物料运动的影响EI北大核心CSCD

镀桶的截面形状对机械镀过程的影响受限于机械镀设备等原因,相关研究较少。为研究不同截面形状的镀桶对机械镀过程中桶内物料运动规律的影响,采用离散元模拟软件EDEM建立不同形状(四边形、六边形、八边形、圆形)下镀桶内物料的运动模型,并从碰撞区域、碰撞频率、碰撞接触力和碰撞能量四个方面对桶内物料间的碰撞情况进行研究。结果表明:镀桶的截面形状对机械镀过程中桶内物料的碰撞和运动规律产生很大影响,在相同模拟条件下,八边形镀桶内物料运动的惰性区域最小;通过对不同形状镀桶内物料间碰撞频率、碰撞接触力和碰撞能量的对比分析,八边形镀桶中的物料运动规律最有利于机械镀工艺过程中镀层的形成和增厚,八边形为最优镀桶截面形状。另外,通过计算机数值模拟的方法探讨镀桶截面形状对机械镀过程中物料运动规律的影响规律,为机械镀设备发展和工艺优化提供理论依据。     

Efficiency in Barrel Plating

Barrel efficiencies have been measured for the electroplating of three sizes of wire nails in a small plating barrel in nickel, zinc, and copper sulphate and pyrophosphate solutions. The results have shown that the barrel efficiency is affected by the effective current density, speed of barrel rotation, type of solution, type of load and degree of volume loading but not by the coating thickness. The reproducibility was best for copper pyrophosphate while zinc had the highest and nickel the lowest cathode current efficiency.     

Nickel multilayers and their effects on bend fatigue strength of leads

Nickel is commonly coated on the outer leads for T8 metal package. The leads electrodeposited by conventional dull or bright nickel over 5 μm at direct current from Watt bath are hard to pass the bend fatigue test for three times. Nickel electrodeposited at multi waveform current including direct current, single and double pulse from sulfamate bath can improve the bend fatigue strength of leads. Such nickel plating has a multilayer structure, its morphology of sublayers can be clearly seen in its cross section with SEM. The electrochemical study shows that these sublayers have different corrosion potentials. The bend fatigue test of leads with such plating for T8 metal package shows that the number of bend increases with the decrease of average current density of multi waveform, which can be attributed to the reduction of every sublayer thickness and the increase of layer numbers under the same condition of total thickness.     

先导金属在镀锌合金化过程中作用机理的研究

主要通过观察试验,并借助于扫描电子显微镜,结合物理化学、电化学的基础理论知识,对机械镀锌合金化过程中先导金属的作用机理进行了研究.从金属粉的合金化、铁基表面的合金化、镀层的合金化及枝晶生长理论4个方面分析了先导金属对机械镀锌合金化过程的影响.结果表明,机械镀锌合金化过程中先导金属的确起着非常重要的作用,而且先导金属可以促进机械镀锌镀层的结合强度,可以用先导金属的作用机理解释机械镀Al、Zn时的各个过程.     

纳米Ti膜形成过程的扫描隧道显微镜观察

用磁控溅射方法在聚合物薄膜基体上制备出不同厚度的纳米Ti膜,扫描隧道显微镜（STM）的观察结果表明,初期膜是由直径小于2nm的形核粒子和粒子团聚体组成,粒子沉积呈岛状生长形成纳米晶粒结构,随薄膜厚度增加,平均晶粒尺寸增加,形成大尺寸晶粒的连续薄膜,分析和讨论薄膜生长过程的结构特征及溅射条件对薄膜结构的影响。     

Improvement of thickness uniformity in nickel electroforming for the LIGA process

An effective method to improve thickness uniformity in nickel electroforming for the LIGA process to produce metallic microstructures is described. The deposited metal distribution is naturally a concave shape over the whole area of the plating base proved by experiments. The edge thickness of the plating area is usually twice or higher than the center of the plating area. A secondary cathode (guard ring) was applied to improve the electroform uniformity. The experimental result of a Joule–Thomson micro-cooler proved its feasibility. The thickness ratio of edge to center of a 500 μm sample decreased from 2.5 to 1.4. The thickness uniformity improvement is achieved without a loss in plating rate in the center of the features.     

Effects of rare earth cerium addition on the synthesis and corrosion resistance of electroless Ni–PTFE–P coating

Electroless Ni–PTFE–P coatings have been successfully deposited on the surface of mild steel shaft from plating baths containing various concentrations of rare earth metal cerium (RE Ce). Surface morphology, Ce fraction, and thickness of the coatings were characterized by scanning electron microscope, inductively coupled plasma optical emission spectrometry, and reflection optical microscope, respectively. Salt spray test was used to determine the corrosion resistance of the coating. Results revealed that structure, compactness, and deposition rate of the Ni–PTFE–P coatings were increased significantly by addition of a small amount of RE Ce (10–20 ppm) to the plating bath. Electroless Ni–PTFE–P coating deposited from plating baths with 20 ppm Ce shows the highest corrosion resistance, owing to its high compactness and thickness. Deposition rate and corrosion resistance of the Ni–PTFE–P coating were deteriorated greatly as concentration of RE Ce in the plating baths exceeds 100 ppm.     

黄铜箔拉伸屈服强度的尺寸效应

为了研究金属箔的塑性变形性能与尺寸的相关性,在常温下对不同厚度和晶粒尺寸的黄铜箔试样进行了单向拉伸实验.结果表明:随着厚度或晶粒尺寸的减小,箔的屈服强度都会升高,晶粒尺寸对屈服强度的影响满足Hall-Petch细晶强化关系,厚度减小使屈服强度升高也可以主要归结于晶粒尺寸的减小.此外,当箔的厚度小于100 靘时,厚度/晶粒尺寸比不能表征屈服强度的尺寸效应.     

Back Matter

The inherent difficulties of plating zinc alloy die-castings can only be overcome if care is taken at every stage, beginning with the actual design of the castings. The die-casting technique and the polishing operations are just as important to the plater as the processes directly under his control. From special solutions, nickel may be deposited directly, although usually the deposit obtained is less satisfactory and the plating control more critical than with ordinary nickel solutions. Preliminary deposition of copper is of more general application, and the introduction of the Rochelle-salt solution has removed many of the difficulties previously associated with cyanide-copper plating. This solution requires careful operation, but the results obtainable justify the extra control needed. If a few pre- cautions are taken, chromium, silver, brass and metal colour finishes may be deposited without difficulty.     

Plasma and ion-beam-assisted deposition of multilayers for tribological and corrosion protection

Multilayers of Ti/TiN and Al/AlN were deposited on steel and silicon by magnetron sputtering and ion-beam-assisted deposition. Compositions and film thicknesses were determined by Rutherford backscattering. Hardness was measured with a dynamic ultramicrohardness tester. The corrosion protection potential in an aqueous environment was evaluated by electrochemical techniques. The results are discussed in terms of the structure and composition of the multilayer arrangement. It turns out that the multilayer coatings generally show a better corrosion protection performance than both the pure metal and the pure nitride films, with an optimum ratio of nitride film thickness to metal film thickness for a maximum corrosion protection effect. The hardness values are in between that of nitride single film and those of metal single films. Deposition of multilayers with the possibility of selecting the thickness ratio of metal to nitride film for particular mechanical and chemical requirements allows a controlled adaption of the film features to a given application problem.     

采用旋转电极的金刚石表面镀镍方法及工艺

针对目前常用的固定电极滚镀法存在的镀覆效率低、镀层不均匀等问题,提出基于旋转电极的金刚石表面滚镀方法,并开发相应的滚镀装置。分析金刚石旋转电极滚镀法的镀覆机理,通过试验研究镀覆工艺参数对金刚石表面镀层沉积速率和镀层形貌的影响。结果表明:旋转电极可以驱动磨料堆增加其翻转频率和磨粒间的分散能力,提高磨粒堆与电极和镀液接触的均匀性,从而提高镀层的均匀性和表面质量。采用旋转电极滚镀法的最佳工艺参数为:镀覆电流为4 A,阴极转速为20 r/min,阴极转子直径为22.5 mm,金刚石粒度代号为70/80。增加磨粒堆的翻滚频率使磨粒间接触均匀性得到改善,增大滚镀空间和电极尺寸,进而增加单次镀覆的装载量。结果显示:采用旋转电极滚镀方法在2 L容量镀瓶中最大装载量可达700 g,约为相同条件下的固定电极装载量的2倍,显著提高了金刚石镀镍的生产效率。      

Fe-C-Mo-V堆焊合金的滚动三体磨粒磨损行为研究

通过熔化极气体保护焊技术制备了Fe-C-Mo-V堆焊合金磨损试样,基于滚动三体磨粒环境下进行了干砂橡胶轮磨损试验,利用扫描电子显微镜、能谱分析、维氏硬度计等显微分析和性能测试方法,对Fe-C-Mo-V堆焊合金熔敷金属的磨损失重和磨痕形貌进行检测与表征,研究了不同法向载荷条件下该熔敷金属的磨损行为变化规律.结果表明:随法...     

14Cr9Mo1.5Co1.2VNbNB双钨极氩弧焊堆焊接头成分和性能

对某超超临界汽轮机转子用14Cr9Mo1.5Co1.2VNb NB(FB2)钢进行双钨极氩弧焊(D-TIG),采用化学分析及硬度检测的方式分别测量不同厚度的化学成分和硬度,分析其变化规律;使用光学显微镜(OM)观察和分析堆焊接头的组织,并进行堆焊接头无损检测及力学性能测试。结果表明:在不同堆焊方案下,随着堆焊层厚度增加,堆焊层熔敷金属化学成分逐渐接近焊丝的化学成分,热影响区(HAZ)硬度较高,当达到堆焊层后硬度逐渐均匀;金相图片显示焊缝均无裂纹。堆焊接头无损检测和各项力学性能满足机组性能要求。     

Critical parameters in hot filament chemical vapor deposition of diamond films on tool steel substrates with CrN interlayers

The accomplishment of adherent and continuous diamond coatings on tool steel substrates with CrN interlayers is determined by many key parameters such as appropriate surface finish, interlayer thickness, substrate temperature and system pressure. A detailed study is carried out to probe the effect of these parameters on diamond nucleation and growth. Substrates with different surface finishes are prepared by electrical discharge machining (EDM) and CrN interlayers of various thicknesses are deposited onto these substrates by arc plating. Samples with a CrN interlayer of 2.5 μm are found to provide a continuous diamond film at a low pressure value of about 5 mbar. Nonetheless, the process window for obtaining such diamond layers is small, which results in limited reproducibility.     

Effect of additive concentration during copper deposition using EnFACE electrolyte

Copper deposition from solutions using high concentration of acid, metal ions and polyethylene glycol (PEG), and bis-(3-sulphopropyl) disulphide (SPS) and chloride ions (Cl^–) is well known. A recent maskless micropatterning technology, which has the potential to replace the traditional photolithographic process, called EnFACE, proposed using an acid-free, low metal ion solution which is in direct contrast to those used in standard plating technology. In this work copper has been deposited using both standard electroplating solutions and those used in the EnFACE process. In the standard electrolyte 0.63 M CuSO₄ and 2.04 M H₂SO₄ has been used, along with Gleam additives supplied by Dow Chemicals. For the Enface electrolyte, copper deposition has been carried out without any acid, and with different concentrations of additives between 17% - 200% of those recommended by suppliers. 25?µm of metal has been plated on stainless steel coupons as suggested by ASTM, peeled off and subjected to ductility and resistance measurements. Scanning electron microscopy and electron back scatter diffraction have been carried out to determine the deposit morphology. It was found that copper deposits obtained from acid-free solutions containing low concentration of metal ion and additives produced copper deposits with properties which are comparable to those obtained from standard electrolytes. The optimum additive concentration for the EnFACE electrolyte was 50% of the supplier recommended value.     

Ultrathin Al_2O_3-coated reduced graphene oxide membrane for stable lithium metal anode

Lithium(Li) metal has been considered as the most attractive anode materials for Li-ion batteries(LIBs)due to its high theoretic specific capacity. The formation of unstable solid electrolyte interphase(SEI) and dendritic Li on the metal anode, however, hindered its practical application. Herein, to address the issues, a Li-free electrode with ultrathin Al_2O_3 coated on reduced graphene oxide(rGO) membrane that covers a Cu foil current collector was developed. The composite electrode exhibits excellent interfacial protection of lithium metal deposited between Cu foil and rGO electrochemically. Firstly, it affords good Li~+ permeability from the electrolyte. Secondly, the ultrathin Al_2O_3 has sufficient mechanical strength to inhibit the penetration of Li dendrite. Li metal was observed uniformly deposited between rGO membrane and Cu collector, and stable cycle performance of Li plating/stripping with Coulombic efficiency of ~91.75% at the 100 th cycle is achieved in organic carbonate electrolyte without any additives.     

Optimaler Korrosionsschutz durch Metallüberzüge mit Anstrich und ihr Einfluß auf die Gestaltung der Stahlbauwerke

Optimum corrosion protection by metal coatings and paint coats and their influence on the design of steel structures Systems consisting of metal coatings + paint or plastic coatings are an efficient and economic corrosion protection for steel structures in aggressive atmospheres or soils. The zinc layer should therefore have at least 80 μm in thickness. Paint coats on top of the zinc layer increase the useful life of the latter, provided, however, they are repaired or renewed in time. Although welding such sheet metal or profiles is still difficult, such materials are being used extensively for parts under static load. Their use for parts under dynamic load presupposes a favourable result of fatigue tests which are still in progress. Suitable protection systems for various conditions and sheet thicknesses are listed.