Effects of pulse current on properties of electrodeposited RE-Ni-W-P-SiC composite coating

Effects of pulse current on properties of electrodeposited RE-Ni-W-P-SiC composite coating were studied. The results show that hardness of the pulse current electrodeposited composite coatings is higher than that of the direct current electrodeposited composite coatings while other parameters are the same. Otherwise, the deposited velocity is higher, and wear resistance and corrosion resistance of the pulse current electrodeposited composite coatings are also improved when the average current density is 10 A/dm2 , pulse frequency is 800 Hz and duty ratio is 1: 5. The hardness of the coating as-deposited is HV500 - 700, and it reaches HV1300 after heat treatment at 400 ℃ for 1 h.     

CATHODIC PROCESS AND WEAR RESISTANCE OF ELECTRO-DEPOSITED RE-Ni-W-P-SiC COMPOSITE COATING

Cathodic deposition current density of the composite coatings increases when SiC par-ticles and rare earth (RE) were added in the bath, which is profitable for Ni- W-P alloy to deposit in the cathod, forming Ni-W-P-SiC and RE-Ni-W-P-SiC composite coatings. On the contrary, the addition of PTFE in the bath decreases cathodic deposition current density of the coatings. The current density increases a little when the amount of RE isγ-9g/l; however, the current density increases greatly when the amount of RE is increased to 11-13g/l. But if the amount of RE is raised further, the current density decreases. Hardness and wear resistance of RE-Ni-W-P-SiC composite coating have been studied, and the results show that the hardness and wear resistance of RE-Ni-W-P-SiC composite coating increase with increasing heat treatment tempera-ture, which reach peak values at 400℃; while the hardness and wear resistance of the coating decrease with the rise of heat treated temperature continuously.     

The correlation among deposition parameters,structure and corrosion behaviour of ZnNi/nano-SiC composite coating deposited by pulsed and pulsed reverse current

The present work shows how the parameters of pulsed current (PC) deposition affect structural and morphological characteristics of electrodeposited ZnNi/nano-SiC composite coating and its corrosion properties. In this regard, ZnNi coatings containing SiC nanoparticles were electrodeposited from chloride bath by PC and pulsed reverse current (PRC) methods, and the effect of duty cycle, frequency and reverse current density were studied. With low and high duty cycles the SiC content of the coating was more than the coating deposited by medium duty cycle. Changing the duty cycle affected the coating composition, structure and morphology. Elevation of the pulse frequency increased SiC content of the coating. Application of PRC produced a coating with a complex and dendritic structure. In most of the electrodeposition conditions, in addition to direct effects of PC on coatings characteristics, it was seen that the more SiC was deposited in the coating the less Ni was deposited, and this also affected the corrosion behaviour. The best corrosion resistance behaviour was shown by coatings with more compact structure and less porosity.     

双脉冲电源参数对电铸金刚石-镍复合膜品质的影响

采用电铸法制备了金刚石-镍复合膜,研究了平均电流密度、正向脉冲频率、正向脉冲占空比、反向脉冲占空比等双脉冲电源参数对镀层厚度的均匀性、沉积速率、硬度、表面形貌的影响.结果表明:随着平均电流密度的增加,沉积速率增大并趋于稳定,复合膜硬度先增大后减小,厚度的均匀性变差;随着正向脉冲频率的增加,沉积速率和硬度都增大,厚度的均...     

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.     

Theoretical study of hardness variation with pulse parameters in composite coatings electrodeposited by pulsed currents

Theoretical aspects of the electrodeposition of composite coatings prepared by pulsed currents and also the variation of coatings hardness with the pulse parameters have been presented in this paper. The effect of the grain size, polarisation, pulse-plating parameters and incorporation of ceramic particles on the hardness or flow stress are also reported. The theoretical relationship obtained showed that with increasing polarisation and particle incorporation, the hardness of the coatings was increased. In addition, by decreasing the grain size, frequency and duty cycle the hardness was increased.     

Properties and structure of RE-Ni-W-P-SiC composite coating prepared by impulse electrodeposition

The properties and structure of electrodeposited RE （CeO2）-Ni-W-P-SiC composite coating were investigated. The results show that the hardness and electrodepositing speed of composite coatings obtained at an impulse current are higher than those at a direct current. The hardness and wear resistance of the coating are obviously increased by adding RE and SiC. The hardness of the coating increases with the increase of treatment temperature and current density, and reaches the optimum value at 400 ℃ and at 10 A/dm^2, respectively. The optimum operation parameters of electrodeposition of the composite coating are as follows： pH value is 4.5, bath temperature is 65 ℃, and current density is 10 A/dm^2.     

PROCESS AND PROPERTIES OF ELECTROLESS PLATING RE-Ni-B-SiC COMPOSITE COATINGS

ＰＲＯＣＥＳＳＡＮＤＰＲＯＰＥＲＴＩＥＳＯＦＥＬＥＣＴＲＯＬＥＳＳＰＬＡＴＩＮＧＲＥ－Ｎｉ－Ｂ－ＳｉＣＣＯＭＰＯＳＩＴＥＣＯＡＴＩＮＧＳ￥ＧＵＯＺｈｏｎｇｃｈｅｎｇ;ＬＩＵＨｏｎｇｋａｎｇ;ＷＡＮＧＺｈｉｙｉｎ;ＷＡＮＧＭｉｎ（ＫｕｎｍｉｎｇＩｎｓｔ...     

脉冲参数对等离子电沉积镍镀层结构和性能的影响

采用高频脉冲电源在纯铜基材上以等离子电沉积技术制备出了金属镍镀层,研究了高频脉冲频率以及占空比变化对等离子镀镍层结构和性能的影响。对镀层进行了SEM,显微硬度以及划痕结合力的表征。结果表明,随着高频脉冲频率和占空比的增加,镀层表面的熔融态形貌逐渐减少,镀层逐渐变得致密,表面硬度与结合力值也相应提高。通过讨论脉冲电源的能量作用方式,分析了频率及占空比对等离子电沉积镍层表面结构及性能的影响规律。     

脉冲电刷镀Ni-Co镀层及其硬度的研究

目的优选脉冲参数,获得具有较高显微硬度的电刷镀Ni-Co合金镀层。方法采用脉冲电源制备电刷镀Ni-Co合金镀层,以显微硬度为性能指标,对比考察CoSO_4浓度、电压、频率和占空比对Ni-Co合金镀层的影响,并研究了最优工艺参数下Ni-Co-MoS_2复合镀层硬度随MoS_2浓度的变化情况。结果电刷镀Ni-Co合金镀层的显微硬度随镀液中CoSO_4浓度的升高先增大后减小,当CoSO_4质量浓度为40 g/L时,镀层硬度达到最大值597.4HV。在4~12 V范围内,电压的增大以及占空比的减小,会使镀层硬度增大。随着频率的增大,镀层硬度呈增大趋势;频率达到1200 Hz后,镀层硬度轻微下降。加入一定量MoS_2,复合镀层硬度先增后减。结论在CoSO_4质量浓度为40 g/L、电压12 V、频率1000 Hz、占空比0.5的条件下,制备出的镀层硬度最大。与未加MoS_2的电刷镀Ni-Co镀层相比,Ni-Co-MoS_2复合镀层硬度有所下降;随着MoS_2浓度增加,复合镀层硬度先增大后减小,当MoS_2质量浓度为20 g/L时,复合镀层硬度达到最大值547HV。     

占空比对高频脉冲电沉积( Ni-Co) / 纳米 Al2O3复合镀层的影响

采用高频脉冲电沉积法制备(Ni-Co)/纳米Al2O3复合镀层,研究了占空比对复合镀层沉积速率、成分、形貌及表面显微硬度的影响。结果表明:随着占空比由0.3提高至0.5,复合镀层的沉积速率增加,晶粒尺寸变大,表面变粗糙,并且Co含量降低,Ni含量增加,纳米Al2O3颗粒含量变化不明显,Co含量的降低导致硬度降低。     

Ni/n-SiO2 Composite Coating Prepared by Brush Plating with Pulse Current

Nickel and silicon dioxide nanoparticle composite coatings were prepared by brush plating with direct and pulse current.The surface morphology,microstructure,hardness and wear resistance of the coatings were investigated by scanning electron microscope(SEM),transmission electron microscope(TEM),mirohardness tester and ball-on-disk tribotester.The results show that the technical parameters,pulse current,duty circle and frequency,are of great influence on the growth of crystalline and properties of the coating.Compared with the coating plated with direct current,the coatings plated with pulse currents have smaller nanocrystalline,contain more SiO2 nanoparticle and have higher hardness and wear resistance.     

Ni-P-PTFE化学复合镀的工艺研究

用化学镀的方法制备了Ni-P-PTFE复合镀层.为了确定合适的工艺,研究了Ni-P-PTFE化学复合镀的工艺中温度、pH值、表面活性剂等参数对镀速、镀层中PTFE含量和硬度的影响.试验表明:温度和pH值升高,镀速增大,PTFE含量先升高再降低,硬度下降;FC4表面活性剂的加入量增大,镀速下降、PTFE含量先升高再降低,硬度下降.在此基础上确定了工艺参数,温度85℃,pH值4.4～4.6,PTFE含量 8mL/L ,FC4表面活性剂的加入量为0.4g/L.     

电沉积参数对Co-BN（六方、）纳米复合涂层显微组织和摩擦性能的影晌

通过扫描电镜、场发射扫描电镜、能谱、原子力显微镜和X射线衍射等测试技术,研究电流密度、占空比和频率对电沉积Co—BN（六方）纳米复合涂层的显微组织和BN粒子含量的影响。同时,研究其显微硬度、摩擦性能以及磨损机理。随着电流密度和频率的增加,涂层的BN粒子含量和显微硬度先增加后减少。另外,通过减少占空比,可以沉积更多的BN粒子并且得到更高的显微硬度。在占比空10％,频率50Hz和电流密度100mA／cm2的条件下,可以得到最佳的涂层摩擦性能。     

Pulse TIG Welding of Two Al-Mg-Si Alloys

This article reports the influence of pulse tungsten inert gas (TIG) welding parameters on the microstructure, hardness and tensile strength of weld joints of two Al-(0.5-0.8%)Si-(0.5-0.6%)Mg alloy (T4) produced by using three pulse frequencies (25, 33, and 50 Hz) and two duty cycles (40 and 50%). It has been observed that the mechanical properties (hardness and tensile strength) are sensitive to microstructure of weld metal, which is appreciably affected by the pulse parameters. Low frequency produced higher strength and hardness than high pulse frequency under identical welding conditions. Weld metal and HAZ were found stronger than the base metal. SEM study showed that the fracture of weldment was mostly brittle type.     

稀土对复合镀工艺及镀层性能的影响

研究了稀土对复合镀工艺及性能的影响，结果表明，添加适量的稀土能显著地提高复合镀层中ＳｉＣ微粒的含量，硬度和耐磨性。     

占空比对氨基磺酸盐制备 Ni-TiN 纳米复合镀层性能的影响

目的进一步提高电沉积制备Ni-TiN纳米复合镀层的性能。方法选用氨基磺酸盐镀液体系,利用超声脉冲方法在3Cr13基体上电沉积Ni-TiN纳米复合镀层,研究占空比对纳米复合镀层TiN含量、表面形貌、显微硬度、微观结构的影响。结果随着占空比增加,镀层的硬度和纳米TiN含量先增加,后降低,镀层织构衍射强度增加,结晶度提高,衍射峰变窄。在占空比为0.2时,镀层TiN含量和硬度达到最大值,TiN质量分数为3.85%,硬度为580HV0.1,且镀层表面平整、致密。结论在一定的平均电流密度下,采用合适的占空比可以获得表面平整、致密的Ni-TiN纳米复合镀层。纳米TiN的共沉积影响了镍的结晶过程,不同占空比下制备的镀层中纳米TiN含量不同,引起了镀层晶格畸变,织构发生明显变化,性能改变。     

替代电镀铬的碳化硅类复合电镀技术研究进展

针对目前工业应用中对替代电镀铬工艺的绿色表面技术需求,介绍了物理气相沉积、热喷涂、冷喷涂、超高速激光熔覆、复合电镀技术的原理、特点、应用,以及替代电镀铬工艺的优势和局限性,重点对碳化硅类材料复合镀技术的研究进展进行了综述,介绍了Ni-SiC、Cu-SiC、Zn-SiC、Ni-P-SiC、Ni-SiC-GO镀层的主要应用,及电解液组分中添加石墨烯和氧化石墨烯以提高复合镀层腐蚀性能的作用和机理.介绍了电解液pH值、温度、浓度对镀层性能的影响,不同的电解液体系中,当pH值、温度、浓度达到最优值时,镀层性能可达到最佳.介绍了SiC颗粒尺寸以及分散方式对镀层性能的影响,颗粒尺寸过小,易发生团聚,颗粒尺寸过大,沉积量降低,通过添加剂和物理搅拌,可以有效解决颗粒团聚的问题,提高颗粒沉积量,从而改善镀层性能.介绍了电源参数对复合镀层性能的影响,复合镀工艺中应当优化电流密度、电模式(脉冲和直流)和占空比等参数.最后,总结了碳化硅类材料复合镀技术的发展趋势,即工艺设计向绿色环保化、镀液体系向多元复合化、工艺控制向智能化方向发展.     

超声条件下脉冲电镀 Ni-纳米 Al2 O3 复合镀层及其显微硬度研究

目的优选脉冲参数,以获得具有较高显微硬度的复合镀层。方法超声条件下,采用脉冲电镀方法制备Ni-纳米Al2O3复合镀层。以显微硬度作为性能指标,对比考察平均电流密度、占空比、频率和施镀时间的影响。结果 Ni-纳米Al2O3复合镀层的显微硬度随着平均电流密度升高,占空比增大,频率升高,均呈现出先增后减的趋势,而随着施镀时间延长,呈现出近似递减的趋势。结论在平均电流密度8 A/dm2、占空比0.6、频率1.5 k Hz、施镀时间3 min的条件下,制备的Ni-纳米Al2O3复合镀层显微硬度最高,约为427.1HV。较高复合量的纳米微粒有效起到了弥散强化和细晶强化作用,改善了复合镀层结构致密程度,进而提高了显微硬度。     

Influence of pulse plating parameters on morphology and hardness of pure tin deposit

Abstract

In the present work, the electrochemical deposition of tin coatings using pulse plating techniques was investigated. Based on fundamental electrochemical experiments, pure tin coatings were deposited by using direct and pulsed current. Both types of deposits were compared with each other and the effects of the pulse plating parameters, i.e. duty cycle, frequency and current density were investigated. Matt layers with wide powdery areas are obtained with direct current. At low current density and low duty cycle (10%), the pulsed current improves this aspect of the deposit by reducing the formation of powdery deposits. At higher duty cycles, the increase in the frequency additionally improves the hardness of the coating.