Electrodeposition and characterization of Cu-Nb composite coatings

Copper coatings containing well-distributed Nb particles were obtained by co-electrodeposition in an acidic sulfate bath. Nb particle concentration in the bath was the most significant factor for the incorporation of Nb particles in copper, followed by stirring rate, whereas current density presented low significance. High Nb particle concentration and low stirring rate led to a higher incorporated Nb particle content. The microhardness of the composite layers was higher than that of pure copper deposits obtained under the same conditions due to copper matrix grain refinement and increased with the increase of both current density and incorporated Nb particle volume fraction. The corrosion resistance of Cu-Nb composites in 0.5 wt.% H₂SO₄ solution at room temperature was higher than that of pure copper and increased with the increase of the Nb content.     

Preparation of nanostructured Ni/Al2O3 composite coatings in high magnetic field

Ni/Al₂O₃ composite coatings were prepared by a novel method from a modified Watt's type electrolyte containing nano-Al₂O₃ particles, where a high magnetic field was imposed in the direction parallel to an electrolytic current instead of mechanical agitation. Effects of magnetic field on the content of particles, surface morphology, microhardness and wear resistance of plating layer were investigated. It was found that the high magnetic field played an important role in the formation of composite coatings. The amounts of nano-Al₂O₃ particles in the composite coating increased with increasing of magnetic flux density and reached a maximum value at 8 T, then reduced slightly. The microhardness and wear resistance of the nanocomposite coatings also enhanced with increasing of magnetic flux density as compared to that of pure Ni coating fabricated in the absence of magnetic field. That was because the co-deposited nano-Al₂O₃ particles were uniformly distributed in the Ni matrix and contributed to greatly increase the microhardness and wear resistance of the composite coatings. Moreover, the mechanism of action of high magnetic field was discussed preliminarily.     

Electroless ternary Ni-W-P alloys containing micron size Al2O3 particles

In the present investigation electroless ternary NiWP-Al₂O₃ composite coatings were prepared using an electroless nickel bath. Second phase alumina particles (1 µm) were used to codeposit in the NiWP matrix. Nanocrystalline ternary NiWP alloys and composite coatings were obtained using an alkaline citrate based bath which was operated at pH 9 and temperature at 88 ± 2 °C. Mild steel was used as a substrate material and deposition was carried out for about 4 h to get a coating thickness of 25 ± 3 µm. Metallographic cross-sections were prepared to find out the coating thickness and also the uniform distribution of the aluminum oxide particles in NiWP matrix. Surface analysis carried out on both the coatings using scanning electron microscope (SEM) showed that particle incorporation in ternary NiWP matrix has increased the nodularity of composite coatings compared to fine nodular NiWP deposits. Elemental analysis of energy dispersive X-ray (EDX) results showed that codeposited P and W elements in plain NiWP deposit were 13 and 1.2 wt.%, respectively. There was a decrease in P content from 13 to 10 wt.% with a marginal variation in the incorporated W (1.01 wt.%) due to the codeposition of aluminum oxide particles in NiWP matrix. X-ray diffraction (XRD) studies carried out on as-plated deposits showed that both the deposits are X-ray amorphous with a grain size of around 3 nm. Phase transformation studies carried out on both the coatings showed that composite coatings exhibited better thermal stability compared to plain NiWP deposits. From the XRD studies it was found that metastable phases such as NiP and Ni₅P₂ present in the composite coatings heat treated at major exothermic peak temperature. Annealed composite coatings at various temperatures revealed higher microhardness values compared to plain NiWP deposits.     

Effects of SiC Volume Fraction and Particle Size on the Deposition Behavior and Mechanical Properties of Cold-Sprayed AZ91D/SiCp Composite Coatings

AZ91D/SiC_p composite coatings were fabricated on AZ31 magnesium alloy substrates using cold spraying. The effects of SiC volume fraction and particle size on the deposition behavior, microhardness, and bonding strength of coatings were studied. The mean sizes of SiC particles tested were 4, 14, and 27 μm. The results show that fine SiC particles (d _0.5 = 4 μm) are difficult to be deposited due to the bow shock effect. The volume fraction of SiC particles in composite coatings increases with the increasing SiC particle size. The microhardness and bonding strength of composite coatings also show increases compared with AZ91D coatings. The volume fractions of SiC particles in the original powder were set at 15, 30, 45, and 60 vol.%. The corresponding contents in composite coatings are increased to 19, 27, 37, and 51 vol.%, respectively. The microhardness of composite coatings also increases as the volume fraction of SiC particles increases.     

Characterization of electrodeposited Ni-TiO2 nanocomposite coatings

Nanocomposites containing titania nanoparticles in a nickel matrix have been prepared by means of electrocodeposition from two different types of nickel plating baths, viz. an acidic sulfamate and an alkaline pyrophosphate bath. The surface charge and sedimentation behavior of the titania particles in these electrolytes were characterized by zeta potential and stability measurements. A maximum particle incorporation of 4.3 wt.% titania was found for the alkaline pyrophosphate bath. The structure and mechanical properties of the coatings have been investigated as a function of the particle content. The surface morphology and microstructure of the nickel matrix was significantly altered due to the presence of titania nanoparticles. In the case of both nickel baths, the Vickers microhardness showed a tendency to increase with the amount of particle incorporation. The wear resistance increased with decreasing current density and due to the particle incorporation.     

喷射电沉积技术制备Co-Cr_3C_2复合镀层的工艺优化

为提高微米级硬质陶瓷颗粒在金属基复合镀层的含量,制备性能优异的防护性镀层,采用喷射电沉积的方法在直流电压下制备了Co-Cr_3C_2复合镀层,利用控制变量法探讨了电流密度、固体颗粒用量、镀液流量以及喷枪移动速度等对镀层中颗粒含量及镀层性能的影响,并分析了各因素的影响机理。同时,分别采用能谱仪、显微硬度计和摩擦磨损试验机对复合镀层的成分、硬度和摩擦因数进行分析,最终确定了制备该复合镀层的较优工艺参数。结果显示:喷头移动速度对颗粒复合量的影响最为显著;颗粒复合量越大,复合镀层硬度越高、摩擦因数越低;在较优工艺参数下制备的Co-Cr_3C_2复合镀层的Cr_3C_2颗粒含量高达23.6%。     

Effect of applied current on the electrodeposited Ni-Al2O3 composite coatings

Nano-sized Al₂O₃ ceramic particles (50 nm) were co-deposited with nickel using electrodeposition technique to develop composite coatings. The coatings were produced in an aqueous nickel bath at different current densities and the research investigated the effect of applied current on microstructure and thickness of the coatings. The variation in some mechanical properties such as hardness, wear resistance, and the adhesive strength of the composite coatings is influenced by the applied current and this was also studied. The morphology of the coatings was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The hardness, wear resistance, and bond strength of the coatings were evaluated by Vickers micro-hardness test, pin-on-disc test, and tensile test, respectively. Results showed that the Al₂O₃ particles were uniformly distributed in the coatings, and the coatings deposited at a current density of 0.01 A/cm² was most favorable in achieving a maximum current efficiency which causes the co-deposition of a maximum amount of Al₂O₃ particles (4.3 wt.%) in the coatings. The increase in Al₂O₃ particles in the coatings increased the mechanical properties of the Ni-Al₂O₃ composite coatings by grain refining and dispersion strengthening mechanisms.     

Effect of Some Operating Variables on the Characteristics of Electrodeposited Cu-α-Al2O3 and Cu-TiO2 Composites

Copper- χ-Al₂O₃, and Copper-TiO₂ composites were electrodeposited from acidic baths containing 150 CuSO₄.5H₂O₂ 50 Na₂SO_4.10H₂O, 25 H₃BO₃ and either 1–20 gl^?1 α-Al₂O₃ or TiO₂ particles suspended in the bath. The effects were studied of particle size, particle concentration and plating conditions on the cathodic polarization, current efficiency, inert particle content in the composite deposit and on the surface morphology and microhardness of the as-received plate. A mechanism of coelectrodeposition of the inert particles with copper could be suggested from measurements of the cathodic polarization. The efficiency of copper electrodepostion from the selected bath was relatively high (98.5%) and was increased further by increasing the current density and by raising the pH of the bath. The inert particle content reached 1.7% for α-Al₂O₃ and 2.3% for TiO₂. At a current density of 0.66A dm^?2, the microhardness of the copper plate approached 100 kgf mm and the inclusion of the inert particles in copper composites led to an increase of about 25% in the microhardness. A further increase in the microhardness of copper-α-Al₂O₃, was achieved by raising of the deposition current density, where it reached 165 kgf mm^?2 at 1.66 A dm^?2. Scanning electron microscopy examination showed a direct correlation between both the inert particles content, their morphological shape and the microhardness of the copper composites.     

结晶器铜板表面耐磨纳米复合镀层的制备及性能

目的提高连铸坯质量,延长结晶器的服役时间,节约铜资源。方法采用纳米复合镀技术在结晶器铜板表面制备了Ni/Al_2O_3纳米复合镀层,并通过扫描电镜(SEM)观察了复合镀层表面形貌。采用单因素变量法研究了镀液中纳米Al_2O_3添加量、阴极电流密度及镀液温度等对纳米复合镀层显微硬度的影响。对结晶器铜板表面的纯Ni镀层和纳米复合镀层进行了摩擦磨损实验。结果在结晶器铜板表面制备出了高硬度、耐磨损的纳米复合镀层。随着镀液中纳米颗粒添加量的增加,镀层的硬度先升高后降低,且当纳米颗粒添加量为40 g/L时,复合镀层的显微硬度达到最大值384HV。因镀液中纳米颗粒的存在,随着电流密度和镀液温度的变化,纳米复合镀层的硬度变化不大。在相同的摩擦磨损条件下,纳米复合镀层和纯Ni镀层的摩擦系数分别约为0.41和0.7,纳米复合镀层的磨损量约为纯Ni镀层的1/2。结论在Ni基镀层中加入纳米Al_2O_3材料,能显著地提高复合镀层的硬度、耐磨损性能。     

纯铜表面氩弧熔覆TiB2/Ni复合涂层组织及耐磨性能

通过氩弧熔覆技术在纯铜表面制备TiB₂增强 Ni 基复合涂层,以改善其耐磨性能. 将钛粉、硼粉和镍粉在球磨机中充分混合,采用氩弧熔覆技术将纯铜表面预置粉末熔化制备出陶瓷颗粒增强镍基熔覆层. 采用X射线衍射仪、扫描电子显微镜、透射电子显微镜分析涂层的物相及涂层中陶瓷颗粒相的组成、分布及结构,利用显微硬度仪和摩擦磨损试验机测试涂层的显微硬度和耐磨性能. 结果表明,熔覆层物相主要包括γ(Ni, Cu)和TiB₂;陶瓷颗粒增强相弥散分布于熔覆层中,其中颗粒相TiB₂以六边形存在,熔覆层内部与基体界面处均无缺陷产生;熔覆涂层具有较高的显微硬度,当(Ti+B)质量分数为10%时,涂层显微硬度高达781.3 HV,与纯铜基体对比,熔覆层显微硬度提高约11.7倍;在相同磨损条件下,随(Ti+B)质量分数的增加,熔覆涂层的摩擦系数及磨损失重先减小后增大;氩弧熔覆原位自生TiB₂陶瓷颗粒增强镍基熔覆层可显著提高纯铜表面的耐磨性能.     

Electrodeposition and characterization of Ni-TiB2 composite coatings

Nickel-titanium diboride (Ni-TiB₂) composite coatings were successfully fabricated by pulse electrodeposition techniques from nickel sulfamate bath containing dispersed submicron TiB₂ particles. The effect of TiB₂ codeposition on the morphological, microstructural, microhardness and anti-corrosive properties of the composite coatings have been investigated by using scanning electron microscopy coupled with energy dispersive spectroscopy system, X-ray diffraction (XRD), vickers microhardness, and electrochemical impedance spectroscopy (EIS) techniques. Incorporation of TiB₂ particles into the nickel matrix has modified the regular crystal growth of nickel. The XRD patterns revealed that the preferred (100) crystallite orientation of pure nickel has been modified into mixed orientations by the enhancement of (111) and attenuation of (200) diffraction intensities by the incorporation of TiB₂ particles into the nickel matrix. Vickers microhardness of the Ni-TiB₂ composite coating is found to be increased which is nearly 3 times higher than pure nickel coating. The results obtained by polarization curves and EIS analysis in 3.5 wt% NaCl solution have shown the improved corrosion resistance properties of Ni-TiB₂ composite coating over pure nickel electrodeposit.     

Microstructure and electromagnetic properties of Al18B4O33w/Co composite particles prepared by electroless plating method

Al₁₈B₄O₃₃w/Co composite particles were prepared successfully through electroless plating Co on Al₁₈B₄O₃₃ whiskers. The growth behavior of the coatings, the effect of the process parameters and the electromagnetic properties of the prepared Al₁₈B₄O₃₃w/Co composite particles were investigated. The reduced Co nucleated first on the pre-activated surface of the whiskers to form insular particles which then grew larger gradually and eventually merged together to form continuous coatings. The reaction rate increased but the mass gain decreased with the increase of the bath pH and the bath temperature. The crystallinity of the deposited Co decreased with the increase of phosphorous content as well as the bath temperature. The effect of loading is much weaker compare to that of bath pH and bath temperature. The permittivity and the permeability of the prepared Al₁₈B₄O₃₃w/Co composite particles are markedly higher than those of the raw Al₁₈B₄O₃₃ whiskers in microwave band. Relaxation resonance is found in the samples with thick Co coatings due to the presence of eddy current, which deteriorates the permeability of the Al₁₈B₄O₃₃w/Co composite particles.     

电流密度对喷射电沉积Co-Ni-Cr3C2复合镀层组织及性能的影响

目的研究不同电流密度下,Co-Ni-Cr3C2纳米复合镀层中纳米Cr3C2的含量变化及其对组织性能的影响,确定最佳电流密度。方法采用喷射电沉积的方法,选择不同电流密度(30、40、50、60 A/dm^2)制备Co-Ni-Cr3C2纳米复合镀层。利用SEM、XRD、显微硬度计、摩擦磨损试验机、3D测量激光显微镜对Co-Ni-Cr3C2纳米复合镀层的形貌、成分、结构、硬度和耐磨性能进行研究,并对Co-Ni-Cr3C2纳米复合镀层和Co-Ni合金镀层在不同退火温度下的硬度变化进行比较。结果纳米Cr3C2颗粒的加入未明显改变Co-Ni的异常共沉积,在电流密度为40A/dm^2时,Co-Ni-Cr3C2纳米复合镀层中Cr3C2纳米颗粒的质量分数最高,为12.05%。复合镀层表面凹凸不平,呈瘤状结构。电流密度的增加对复合镀层的成分及相结构影响不大,出现了Co和Cr3C2的衍射峰。Co-Ni-Cr3C2纳米复合镀层的硬度随电流密度的升高,先增大后减小,在电流密度为40 A/dm^2时,硬度最高,为585HV0.05。复合镀层的摩擦系数在电流密度为30、60 A/dm^2时波动较大,在40、50 A/dm^2时波动较小。其磨损体积随电流密度的升高,先减少后增加,在40 A/dm^2时,磨损体积最小。Co-Ni-Cr3C2纳米复合镀层硬度随退火温度的升高,先升高后降低,在退火温度为400℃时,显微硬度最高,为602HV0.05。结论Co-Ni-Cr3C2纳米复合镀层在电流密度发生变化时,其Cr3C2纳米颗粒的沉积量、硬度及耐磨性均发生了变化,在电流密度为40A/dm^2时,沉积量最高,硬度和耐磨性能最佳。此外,Co-Ni-Cr3C2纳米复合镀层在高温退火条件下仍能保持较高的硬度。     

冷喷涂SiC/Al纳米复合涂层的组织结构与性能

为制备基体相晶粒细小、增强相均匀分布的SiC/Al纳米复合涂层,以Al、SiC为原料,采用高能球磨法获得SiC颗粒弥散分布的纳米晶Al基复合材料粉末,利用冷喷涂技术低温成型制备了SiC/Al纳米复合涂层,分析了SiC含量对复合涂层相结构、晶粒尺寸、微观结构、硬度及磨损性能的影响规律。结果表明：冷喷涂可实现球磨纳米晶复合粉末结构的原位移植,所制备SiC/Al纳米复合涂层组织致密,微米及亚微米级SiC弥散分布在纳米晶Al（约80 nm）基体之上;SiC颗粒对Al基体有明显强化作用,冷喷涂SiC/Al纳米复合涂层的硬度随SiC体积分数的增加而显著增加,50% SiC/Al纳米复合涂层的硬度高达515 HV_0.3,约为Al块材的13倍;冷喷涂SiC/Al纳米复合涂层的耐磨损性能随着SiC含量增加而显著提高,涂层磨损失效机制为磨粒对基体的切削犁沟变形。     

Effect of the plating parameters on the electrodeposition of Ni matrix coatings containing Ti nanoparticles

This work focuses on the production of electrodeposited nickel matrix composite coatings containing Ti nanoparticles and on the modification of the process parameters in order to maximise the codeposited particles content as well as obtaining a uniform distribution along the coating thickness. The deposition was carried out using a Ni sulphamate plating bath with different amounts of Ti nanoparticles. The plating parameters such as current density, current type (direct, DC, or pulsed, PC) and the use of ultrasound during the deposition have been modified. The specimens produced have had their microstructure, chemical composition and microhardness analysed. It was found that the increase of the particle concentration in the plating bath up to 40?g?L^?1 leads to an increase of the amount of codeposited particles. The use of ultrasound prevents agglomeration of the particles, leads to a more uniform distribution and increases the Ti content. However, it induces microstructural defects in the matrix. These defects can be limited by increasing the current density or by using pulsed current.     

Reactive oxide-dispersed Ni3Al intermetallic coatings by sediment co-deposition

Ni–Al-reactive oxide (REO) ternary composite coatings were successfully deposited from a Watt's nickel bath containing Al particles and REO particles via the sediment co-deposition (SCD) technique. Three different composite systems, Ni–Al-nano CeO₂, Ni–Al-5 μm CeO₂, and Ni–Al–Y₂O₃ (<1 μm), were studied. The volume fraction of the Al particles in the composite coatings was significantly decreased with an increase of the REO bath loading, while the REO particle content positively increased. The REO particles in the plating bath evidently interfered with the deposition of Al particles. The development of intermetallic phases in the annealed Ni–Al-REO composite coatings mainly depended on the Al content in the coatings. REO-dispersed Ni₃Al intermetallic coatings could be formed as long as the REO particle loading in the bath was controlled below a critical level. Transformation of CeO₂ phase to CeAlO₃ was found in the Ni–Al-nano CeO₂ composite coatings during the annealing treatment at 800 °C.     

Cavitation erosion of electroplated nickel composite coatings

The cavitational wear resistance of electroplated nickel composite layers was tested following ASTM G32. Particles of different hardness (titania and silicon carbide) and different sizes from micro-scale to nano-scale were incorporated up to 30 vol.% into a nickel matrix. Martens hardness is improved by grain refinement via particle incorporation. Compared to pure electroplated nickel films the composite layers strengthened by submicro-scale silicon carbide particles exhibit a decreased mass loss of one order of magnitude after 8 h testing time. Remarkably, layers with nano-scaled titania particles show a similar performance.

Apart from particle adherence failures, reduced mass loss of the composite layers correlate with improved hardness of the composite due to grain refinement of the matrix and dispersion hardening effects.     

Improvement in the properties of nickel by nano-Cr2O3 incorporation

Nano-ceramic composite coatings were prepared by the electrodeposition method using sulphamate electrolyte. Nickel was chosen as the metal matrix and nano-Cr₂O₃ particles were chosen as the reinforcement. The surface morphology and the particle distribution in the coating were analysed using field emission scanning electron microscope (FESEM). The particle content was obtained using energy dispersive X-ray analysis (EDAX). A change in the surface morphology of Ni was seen on the incorporation of Cr₂O₃ particles. The coatings were characterized for their structure and no change in the diffraction pattern was seen between plain Ni and Ni-Cr₂O₃ composite. The mechanical property like microhardness and tribological behaviour of the nano-composite coatings was studied and it was observed that the incorporation of Cr₂O₃ particles enhanced the mechanical properties of Ni matrix. The nano-composites were analysed for their thermal stability and corrosion resistance. An improvement in thermal stability was observed but no change in the corrosion behaviour of Ni was seen on the incorporation of nano chromium oxide particles.     

Electrodeposition and heat treatment of nickel/silicon carbide composites

Electrodeposited Ni/SiC composite coatings were obtained in a Watts-type bath. The effect of fine SiC particles on polarization curves of the cathodic reduction of nickel ions was discussed. The incorporation of the particles into the deposit with respect to current density and SiC concentration in the bath was tested. Cathodic current efficiencies were also calculated. Structure of as-plated and heat-treated Ni/SiC composites were examined by means of metallography observations as well as scanning and transmission electron microscopy methods. Two phase transformations in the temperatures range of 20-700 °C were found. For annealed samples, Ni₂Si and Ni₃Si₂ phases were identified. Hardening of the Ni/SiC composites as a function of the particle content in the deposit and annealing temperature was determined by means of the microhardness testing method.     

Nickel and nickel-phosphorous matrix composite electrocoatings

Nickel and nickel-phosphorous matrix composite coatings reinforced by TiO₂, SiC and WC particles were produced under direct and pulse current conditions from an additive-free Watts' type bath. The influence of the variable electrolysis parameters (type of current, frequency of current pulses and current density) and the reinforcing particles properties (type, size and concentration in the bath) on the surface morphology and the structure of the deposits was examined. It is demonstrated that the embedding of ceramic particles modifies in various ways the nickel electrocrystallisation process. On the other hand, Ni-P amorphous matrix is not affected by the occlusion of the particles. Overall, the imposition of pulse current conditions leads to composite coatings with increased embedded percentage and more homogenous distribution of particles in the matrix than coatings produced under direct current regime.