无裂纹铬层的脉冲电镀

<正>0前言采用传统的直流电镀生成铬层时,铬晶粒的"错位"生长导致铬层出现大量裂纹。这些裂纹的存在,有时是有益的,比如某些活塞需要均匀的微裂纹来"藏"一些润滑油/剂,从而达到减少摩擦的目的。然而,要求高气密性、高耐蚀性的工件则希望能减少铬层裂纹,甚至达到无裂纹。本文采用脉冲电镀工艺,研究无裂纹镀铬的几个重要工艺参数。1原理脉冲电镀实质上是直流电镀的通、断循环过程。传统的直流电镀只有一个参数,即电流或电压。而     

信息动态

0 前言 采用传统的直流电镀生成铬层时,铬晶粒的“错位”生长导致铬层出现大量裂纹.这些裂纹的存在,有时是有益的,比如某些活塞需要均匀的微裂纹来“藏”一些润滑油/剂,从而达到减少摩擦的目的.然而,要求高气密性、高耐蚀性的工件则希望能减少铬层裂纹,甚至达到无裂纹.本文采用脉冲电镀工艺,研究无裂纹镀铬的几个重要工艺参数.     

无氰换向脉冲电铸金的微观结构与性能

采用换向脉冲技术在无氰氯金酸溶液中电铸制备厚金(≥50μm)。对比了直流(DC)、单脉冲(PC)、换向脉冲(PRC)电铸工艺对金层外观、表面形貌、结构和显微硬度的影响。结果表明,电铸金的工艺不同,金的沉积模式也不同。直流和单脉冲电铸所得金粒呈松散的球状堆积,孔隙较大;换向脉冲电铸所得金粒呈紧密的层状堆积,孔隙少。直流金铸层沿(220)、(222)和(311)面择优取向,单脉冲和换向脉冲金铸层均呈(111)面的择优取向。换向脉冲金铸层的显微硬度最高,与晶粒尺寸相比,铸层的致密度对显微硬度的影响更明显。     

氯化物体系三价铬镀铬沉积速率的影响因素

开发了Trich-6561氯化物体系三价铬快速电镀装饰铬工艺,研究了温度、pH、配位剂含量等因素对铬沉积速率的影响,并制定了这些参数的工艺范围。在10 A/dm2电流密度下,镀铬速率达0.2μm/min,优于传统三价铬电镀装饰铬工艺。镀层厚度在0.4μm以上,表面呈蓝白色、光滑、无裂纹,中性盐雾试验120 h或乙酸盐雾试验72 h不变色。     

基于3D打印技术的微沟槽金属铜电铸工艺

提出采用3D打印技术与电铸技术相结合的工艺方法制作微沟槽。首先利用3D打印技术制备具有微沟槽结构的基体,经表面导电处理后制成电铸阴极,然后采用电铸技术加工微沟槽。通过正交试验考察了加工间距、阴极电流密度、搅拌速率、温度等工艺参数对铸层显微硬度的影响,加工出了形貌较好的深为547μm、宽为355μm的微沟槽。通过极差分析得出阴极电流密度是影响铸层硬度的最主要因素。获得最大硬度的最佳工艺条件为:加工间距40 mm,阴极电流密度6 A/dm~2,搅拌速率600 r/min,温度26°C。     

电压对电刷镀三价铬镀层性能的影响

在45钢表面电刷镀得到三价铬镀层,镀液组成和工艺条件为:Cr2(SO4)36H2O 0.4 mol/L,甲酸铵0.5 mol/L,氨基乙酸0.5 mol/L,H3BO30.6 mol/L,NaH2PO2 H2O 0.3 mol/L,pH=1.5,温度50°C,镀笔移动速率15 cm/s。研究了电压对镀铬层显微结构、表面粗糙度、厚度、显微硬度和耐磨性的影响。随电压增大,镀层厚度增大,显微硬度和耐磨性均先提高后降低。电压为14 V时,镀层的表面平整,粗糙度为2.387μm,显微硬度为602 HV,耐磨性最好。     

低温镀铁工艺的优化及故障处理

通过正交试验,以沉积速率、显微硬度、腐蚀速率为评价指标,得出低温镀铁的最佳工艺参数为:ρ(FeCl2·4H2O)=400g/L,θ=50°C,pH=1.0,Jk=14A/dm2。在最佳工艺条件下,镀层的沉积速率为342.50μm/h,显微硬度为707HV,中性盐雾试验中腐蚀速率为0.50g/(m2·h),其结合力好,表面光亮,无针孔或结瘤。提出了低温镀铁的故障处理方法。     

2A12铝合金硬质阳极氧化工艺研究

采用正交试验分析了2A12铝合金硬质阳极氧化的工艺参数,研究了电流密度、硬质阳极氧化时间及硫酸浓度对膜层显微硬度及厚度的影响规律。结果表明,电流密度对硬质阳极氧化膜厚度影响相对较大,硫酸质量浓度对硬质阳极氧化膜的显微硬度的影响显著。最佳的氧化工艺参数为:电流密度3.0 A/dm~2,氧化时间t为70 min,硫酸质量浓度240 g/L。该工艺参数下得到的硬质氧化膜平均硬度可达352 HV,膜层厚度δ可达60μm,膜层致密,厚度均匀,综合性能优异。     

脉冲喷射电沉积制备钴–碳化铬复合镀层

采用包覆有50%(质量分数)Ni的C_(r3)C_2微米颗粒(粒径3~5μm)为第二相,以脉冲喷射电沉积制备Co–C_(r3)C_2复合镀层。镀液组成和工艺参数为:CoSO_4·7H_2O 430 g/L,C_(r3)C_2 200 g/L,H_3BO_3 30 g/L,NaCl 5 g/L,十六烷基三甲基溴化铵适量,pH=4,温度40°C,电压18 V,镀液流量2.4 L/min,喷头移动速率1.2 mm/s。研究了脉冲参数对复合镀层颗粒复合量、表面粗糙度、显微硬度以及耐磨性的影响,并探讨了颗粒复合量对镀层性能的影响。C_(r3)C_2颗粒的复合量越高,复合镀层的显微硬度就越高,耐磨性也越好,但表面粗糙度增大。最优脉冲参数为:占空比30%,脉冲周期200 ms。所得Co–C_(r3)C_2复合镀层的颗粒含量达11.98%,显微硬度为542.6 HV,摩擦因数为0.443。C_(r3)C_2颗粒在镀层中分布均匀,与基质金属结合牢固。     

工艺条件对柔性挤压电镀无裂纹硬铬电流效率的影响

以航空零件常用材料300M钢为基材,采用柔性挤压电镀(也称摩擦辅助电镀)工艺制备无裂纹的硬铬镀层。镀液组成和工艺条件为:铬酸酐250 g/L,硫酸根离子2.5 g/L,镀液流速3.2 L/min,极间距45mm,占空比80%或85%,阴极转速300r/min或325 r/min,电流密度30~60 A/dm~2,频率5~20 kHz,温度35~55℃,时间3 h。研究了电流密度、温度及脉冲频率对电流效率的影响,并与传统电镀硬铬工艺进行对比。结果表明,柔性挤压电镀铬的电流效率随电流密度升高而升高,随温度升高而降低,随脉冲频率的变化不大。采用本工艺制备的铬镀层表面光亮度接近镜面,致密、均匀,无裂纹。但柔性挤压电镀铬工艺的电流效率略低于传统电镀铬工艺。     

脉冲喷射电沉积纳米晶镍工艺优化研究

采用脉冲喷射电沉积方法在钢基体表面制备了纳米晶镍镀层,研究了占空比、频率、平均电流密度对镀层硬度的影响,并通过正交试验对工艺参数进行优化,用扫描电镜和X-射线衍射仪对镀层表面形貌和晶粒尺寸进行分析。结果表明,制备纳米晶镍镀层的优化工艺参数为:平均电流密度39.8 A/dm2、频率1 000 Hz和占空比20%,此时镀层最致密,硬度最高(530.6 HV),纳米晶镍平均晶粒尺寸最小(13.7 nm)。     

激光重熔纳米晶镍镀层的研究

介绍了喷射电镀的基本原理,采用自行设计制造的喷射电镀设备制备纳米晶镍镀层,并对镀层进行激光重熔处理.重点研究了在直流电源和脉冲电源作用下,电流密度对镀层金属的微观结构的影响,以及采用激光重熔处理对直流纳米晶镍镀层形貌的影响;考察了金属基体、喷射电镀层以及激光重熔后的镀层的显微硬度的变化.研究结果表明:与基体金属相比,喷射电镀层的显微硬度有明显提高;经过激光重熔处理后镀层的显微硬度得到进一步提高.     

Controlled nucleation and growth in chromium electroplating from molten LiCl-KCl

The relationships between the electrochemical parameters (which can be controlled) and the resulting structures of chromium electrodeposits obtained by electrolysing chromous chloride (CrCl₂) dissolved in the LiCl-KCl eutectic have been established. The electrodeposition of chromium under ordinary potentiostatic conditions leads to pure chromium but this is not in a form to provide an adequate protective coating as it is difficult to avoid dendrite formation and low initial coverage together. These limitations can be overcome by the sequential use of a high overpotential pulse to initiate good coverage and continuing electrodeposition at low overpotential to minimize dendrite formation.The structures and morphologies of chromium electroplates were optimized. The good protective coatings that resulted were adherent, coherent and reasonably free of cracks and pores. The macro-and microthrowing powers of the bath were excellent and the high purity of the chromium electroplates led to low (130–280 HV) measured microhardness.This paper was presented at a workshop on the electrodeposition of refractory metals, held at Imperial College, London, in July 1985.     

脉冲电沉积工艺参数对Ni-W-P合金镀层性能的影响

针对传统镀硬铬沉积速率低、污染环境等问题,采用脉冲电沉积方法在碳钢表面制备Ni-W-P代铬镀层。采用显微硬度计、扫描电子显微镜、X射线衍射仪和电化学工作站研究了脉冲频率、平均电流密度和占空比对镀层性能的影响。结果表明:随着脉冲频率、平均电流密度和占空比的增加,镀层的硬度和耐蚀性均呈现出先增大后减小的变化规律;当脉冲频率为250Hz,平均电流密度为4.0A/dm2,占空比为30%时,镀层为非晶态结构,表面光滑、平整,结构致密,硬度可达5 140MPa,耐蚀性较好。     

A study on the electrocodeposition processes and properties of Ni�CSiC nanocomposite coatings

Ni–SiC nanocomposite coatings were prepared on a brass substrate by electrocodeposition. The electrodeposition was carried out by adding the SiC nanoparticles to a nickel-containing bath. Nickel deposition processes were analyzed by cathodic polarization curves, and the plating parameters were determined preliminarily by analyzing the effects of different technological parameters on the deposition process. Then, electrocodeposition processes were carried out with different concentrations of SiC nanoparticles in the bath. The effects of current density, stirring rate, and SiC nanoparticle’s concentration in the plating bath on the hardness of coatings were investigated by microhardness tests. Besides the microhardness tests, wearing tests and corrosion tests were also applied to the coatings with the highest hardness and coatings of pure nickel. The structures and surface morphologies of the coatings were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The experimental results show that the microhardness of the codeposited coating increases with increasing current density and attains a maximum at the SiC concentration of 6 g/L. The decrease in the microhardness at higher SiC concentrations may be due to agglomeration of nanosized particles in the plating bath. Increasing the stirring speed did not give a better quality deposition as coatings produced at low stirring rates always had higher microhardness values than did those at high stirring rates. Furthermore, the Ni–SiC nanocomposite coatings have lower friction coefficient and better corrosion resistance than those of pure nickel coatings.     

W-Ni-Fe合金镀层与硬铬镀层耐磨性的对比试验

国内煤矿机械设备常采用镀铬的方法来提高工件表面的耐磨性,本文在27SiMn钢基体上制备了W-Ni-Fe合金镀层和硬铬镀层,利用显微硬度计、厚度仪等测试了硬铬和镍-铁-钨合金两种镀层的硬度、厚度,并用摩擦磨损试验机测试了两种镀层的耐磨性能并分析了实验结果。实验结果表明:在相同环境和试验条件下,热处理后的W-Ni-Fe合金镀层硬度不亚于硬铬镀层,且在一定载荷范围内,其耐磨性能优于硬铬镀层。     

Preparation and investigation of pulse co-deposited duplex nanoparticles reinforced Ni-Mo coatings under different electrodeposition parameters

In this work, Ni–Mo–SiC–TiN nanocomposite coatings were deposited on aluminium alloy by pulse electrodeposition with various electrodeposition parameters. The influences of the pulse frequency and duty cycle on the phase structure, morphology, mechanical and corrosion performance of the coatings were systematically investigated. The results showed that with increasing pulse frequency and decreasing duty cycle, the content of embedded duplex nanoparticles increased, and the grains refined gradually. The nanocomposite coating that was prepared at 20% duty cycle and 1000 Hz pulse frequency exhibited compact, uniform, and fine microstructures with the maximum incorporation of nanoparticles (6.81 wt% TiN and 1.72 wt% SiC). The wear rate and average friction coefficient then declined to 4.812 × 10^?4 mm³/N·m and 0.13, respectively, with a maximum microhardness of 519 HV. Simultaneously, the corrosion current density was reduced to 3.11 μA/cm², and a maximum impedance of 34888 Ω cm² was exhibited. The uniformly distributed duplex nanoparticles acted as a hindrance, which consequently supported the enhancement of corrosion and wear resistance. By investigating the variation of the pulse diffusion layer with electrical parameters, it was discovered that when the crystallite size is equivalent to or smaller than the diffusion layer thickness, it would be easier to cross the diffusion layer to incorporate in the coating. Additionally, the effects of various duty cycles and pulse frequencies on the nucleation process of the grains were discussed.     

TiCN涂层的制备及其微观结构和性能

采用直流磁控溅射法在AZ31镁合金上制备了TiCN涂层.采用X射线荧光光谱仪、扫描电镜和X射线衍射仪表征了涂层的化学成分、表面形貌和物相,并采用电化学阻抗谱、浸泡试验、显微硬度测试和磨损试验考察了基体偏压(-40、-60和-80 V)对涂层性能的影响.结果表明,涂层由TiCN和TiN组成.随着负偏压增大,涂层中Ti、C...     

Cr–C/h-BN 自润滑复合镀层的制备与摩擦学性能

在三价铬Cr–C镀液中添加1~5 g/L的h-BN自润滑微粒,运用直流电沉积技术在Q235碳素结构钢基体上制备了Cr–C/h-BN复合镀层。利用扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度计、摩擦磨损试验机等设备分析了h-BN微粒添加量、电流密度等工艺参数对镀层组织和性能的影响。结果表明:在电流密度20 A/dm2,h-BN添加量3 g/L的条件下,可获得h-BN微粒体积分数为6.15%的复合镀层。h-BN微粒的添加改善了Cr–C合金镀层的耐磨性,Cr–C/h-BN复合镀层在室温干摩擦条件下的磨损率减少了22%,平均摩擦因数由原先的0.49降低至0.31。     

Microstructure,adhesion, and tribological properties of conventional plasma-sprayed coatings on steel substrate

A variety of metallic and oxide coatings were deposited under various conditions on 1020 mild steel substrate by conventional plasma spraying. The coating thickness, microhardness, cohesion and adhesion failure loads, friction coefficient, and abrasive wear resistance were evaluated. The coatings were classified as follows, in order of decreasing microhardness and wear resistance: alumina, chromia, 316 stainless steel, Ni-5% Al, elemental aluminum and aluminum-polyester. Wear resistance increased with increasing microhardness and decreasing friction coefficient. The microhardness and wear resistance of high-velocity oxy-fuel (HVOF) diamond jet (DJ)-sprayed aluminum were found to be superior to those of plasma-sprayed aluminum. Plasma or flame-sprayed metallic coatings adhered well to the substrate. The cohesion, adhesion, microhardness, and wear resistance of alumina coatings exceeded those of equally thick chromia coatings.