超声辅助脉冲电沉积Ni-TiN复合镀层的结合力和耐蚀性

超声辅助脉冲电沉积综合了超声波空化效应的解团聚和搅拌作用以及脉冲电流瞬时电流密度高、电流参数可控等特点,是制备纳米复合镀层的有效方法.采用超声辅助脉冲电沉积技术制备了Ni-TiN纳米复合镀层,并用扫描电镜及能谱分析系统、显微硬度计、划痕仪和电化学工作站研究了Ni-TiN复合镀层的微观结构、结合力和耐蚀性.结果 表明:电流密度、脉冲占空比和超声功率对复合镀层中TiN复合量有一定影响.当电流密度为4 A/din2,占空比为40％,超声功率为300W时,复合镀层中TiN粒子复合量为9.98％(质量分数),显微硬度值为741 HV,复合镀层表面晶粒细小、平整致密,复合镀层与基底结合良好,结合力为704.77 MPa;同时复合镀层表现出较优的耐腐蚀性能.     

超声功率对多场耦合作用下脉冲电沉积Ni-ZrO_2纳米复合镀层性能的影响

超声作为解决纳米粒子团聚的有效方法之一,将其引入到磁场-脉冲电沉积中,在磁场-超声耦合作用下脉冲电沉积成功制得了Ni-ZrO_2纳米复合镀层。本工作系统地研究了超声功率对Ni-ZrO_2纳米复合镀层表面形貌、ZrO_2含量、组织结构、显微硬度、耐磨性、耐蚀性能的影响。结果表明,未施加超声时,镀层中ZrO_2含量为6.43%(质量分数),显微硬度为384HV。超声功率从0 W增大到320 W时,复合镀层的性能呈先上升后下降的趋势。当超声功率为240 W时,Ni-ZrO_2纳米复合镀层表面平整致密,晶粒细化,镀层中ZrO_2含量为15.2%(质量分数),显微硬度为494HV,磨损后的表面较光滑,并具有良好的耐蚀性。     

电沉积工艺参数对Ni-TiN-CeO2二元纳米复合镀层中粒子复合量的影响

采用超声-脉冲电沉积法制备了Ni-TiN-CeO2二元纳米复合镀层,研究了工艺参数对镀层中CeO2及TiN粒子复合量的影响,并对镀层的表面形貌及成分进行了测试和分析。结果表明,超声-脉冲电沉积Ni-TiN-CeO2纳米复合镀层的最佳工艺参数为阴极电流密度4A/dm2,TiN粒子添加量15g/L,CeO2粒子添加量40g/L,正向脉冲占空比20%,超声波功率180W。在该工艺条件下,可获得CeO2质量分数为3.3%、TiN质量分数为4.4%的Ni-TiN-CeO2二元纳米复合镀层。同时,TiN与CeO2二元纳米粒子的加入,充分发挥了两种纳米粒子复合的协同效应,优化了粒子与基质金属的共沉积方式,大大改善了镀层质量。     

脉冲电沉积CeO2-SiO2／Ni—W-P纳米复合镀层性能研究

为了探讨脉冲参数对CeO2-SiO2/Ni-W-P四元纳米复合镀层性能的影响,采用脉冲沉积的方法,在普通碳钢表面制备了CeO2-SiO2/Ni-W-P纳米复合镀层.在脉冲关断时间1 000μs和脉冲峰值电流密度30 A/dm2下,研究了脉冲导通时间对纳米复合镀层组织及性能的影响,采用能谱分析、硬度测试、扫描电镜(SEM)等技术对镀层化学组成、沉积速率、显微硬度和表面形貌进行了表征.结果表明,纳米复合镀层中CeO2和SiO2颗粒的质量分数随着脉冲导通时间的延长而增加,当脉冲导通时间为400～600μs时,沉积速率为32.33～38.22μm/h,显微硬度为609～674 HV;脉冲导通时间由100μs增加到400μs时,纳米复合镀层晶粒尺寸降低,但当脉冲导通时间再由400μs增加到1000μs时,纳米复合镀层晶粒尺寸又有所增加.     

超声波对纳米Ni-TiN复合镀层的影响

采用超声-电沉积的方法制备纳米Ni-TiN复合镀层.利用原子吸收分光光度计(AAS)、高分辨率电子显微镜(HRTEM)和X射线衍射仪(XRD)研究超声波对复合镀层含量、显微组织及微观结构的影响.结果表明,超声波的引入,不仅能提高复合镀层中纳米TiN粒子的含量,还能明显改善显微组织结构,细化晶粒.在超声波功率为200W时,镀层中粒子含量达到最大值9.9%.     

超声电沉积法制备Ni-Y_2O_3纳米复合镀层的工艺

Y2O3-Ni复合电沉积层性能优异,用途颇多,但目前有关这方面的研究报道较少.采用超声波技术电沉积制备了Ni-Y2O3纳米复合镀层,考察了制备工艺参数对复合镀层中Y2O3含量和镀层硬度的影响,采用环境扫描电子显微镜(ESEM)对纳米复合镀层的表面形貌进行了分析.结果表明,Y2O3添加量20g/L、Jc 2 A/dm2、超声波功率300 W时,复合镀层的表面组织均匀致密、晶粒细小且显微硬度较高;超声波空化作用产生的微射流可以减少纳米颗粒团聚,提高镀层的性能.     

电沉积Ni-SiC纳米复合镀层的显微组织分析

采用超声波辅助脉冲电沉积复合镀技术在铜基表面制备Ni-SiC纳米复合镀层.研究了超声波的施加和不同电极摆放方式对镀层显微组织和性能的影响.结果表明:超声波和第二相颗粒共同作用可以显著细化复合镀层显微组织,显微硬度可达到HV760;复合镀层镍衍射品面(200)和(220)峰位的变化,说明晶粒生长过程中的择优取向得到了抑制...     

汽车齿轮钢电沉积Ni-TiN镀层的制备及耐磨性研究

采用直流电沉积、脉冲电沉积和超声波脉冲电沉积方法,在汽车齿轮钢20CrMnTi表面制备Ni-TiN镀层。利用扫描电镜、X射线衍射仪、显微硬度计及摩擦磨损试验机等研究Ni-TiN镀层的微观组织、显微硬度和耐磨性能。结果表明,在超声脉冲电沉积获得的Ni-TiN镀层中,金属晶粒得到显著细化,组织结构最为致密,且TiN纳米微粒均匀分布于镀层中,Ni晶粒和TiN微粒的平均粒径分别为76.5和41.4nm。当电沉积时间为50min时,直流电沉积、脉冲电沉积和超声脉冲电沉积制得的Ni-TiN镀层显微硬度分别为841,882和923 Hv,超声波脉冲电沉积Ni-TiN镀层的耐磨性最优。     

纳米金属陶瓷Ni-AIN复合层的超声-电沉积制备

采用超声-电沉积方法制备纳米金属陶瓷Ni-AlN复合层.研究了超声波机械扰动效用对电解液传质过程的作用,超声波空化效应对纳米粒子团聚的抑制作用,脉冲电参数对控制晶粒成核及生长的作用.采用优选工艺参数,在常用金属表面获得了由镍晶(20～60nm)和纳米粒子AlN构成的纳米级Ni-AlN复合镀层.镀层与基体结合比较牢固,结合力达到89 N,厚度11～12μm,平均表面硬度达到HV606.     

用直流和脉冲电沉积制备Ni-Cr纳米复合镀层

应用直流、脉冲电沉积技术分别制备Ni-Cr纳米复合镀层,研究了电沉积方式对其性能的影响。结果表明:随着镀液中Cr浓度的增大.用两种电沉积方式制备的镀层中Cr含量均随着镀液浓度的增加而增加,但是在镀液中Cr浓度相同的条件下脉冲纳米复合镀层的Cr含量比直流纳米复合镀层的高。在900℃氧化24 h后,脉冲纳米镀层的抛物线速度常数低于直流镀层的2.85倍,在含Cl离子和酸性水溶液中其耐蚀性能均优于直流方式制备的纳米复合镀层。脉冲镀层的显微硬度比直流镀层的高2倍。脉冲电沉积能降低镀层表面的浓差极化,控制关断时间,使晶核的形成几率增大,晶核数量增多,从而制备出平整、致密、细化的复合镀层。     

Oxidation behavior of aluminide coatings on carbon steel with and without electrodeposited Ni-CeO2 film by low-temperature pack cementation

A CeO₂-dispersed aluminide coating was fabricated through aluminizing the electrodeposited Ni-CeO₂ nanocomposite film on carbon steel using pack cementation method at 700 °C for 4 h. The isothermal and cyclic oxidation behavior of the CeO₂-dispersed aluminide coating at 900 °C, including the growth of oxide scale and the microstructure of the coatings, have been investigated comparing with the aluminide coating on carbon steel. The results show enhanced oxidation performance of the CeO₂-dispersed aluminide coating, which is concerned with not only CeO₂ effect on the microstructure and oxidation, but also decreased interdiffusion between the aluminide and the Ni film. The CeO₂ benefit effects and interdiffusion are discussed in detail.     

Pulse electrodeposition and corrosion properties of Ni–Si3N4 nanocomposite coatings

The development of modern technology requires metallic materials with better surface properties. In the present investigation; Si₃N₄-reinforced nickel nanocomposite coatings were deposited on a mild steel substrate using pulse current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of Ni and Ni–Si₃N₄ nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of Si₃N₄ particles in the Ni nanocomposite coating on the micro hardness, corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon nitride particles were obtained and the crystal grains on the surface of Ni–Si₃N₄ composite coating are compact. The crystallite structure was face centred cubic (fcc) for electrodeposited nickel and Ni–Si₃N₄ nanocomposite coatings. The micro hardness of the composite coatings (720 HV) was higher than that of pure nickel (310 HV) due to dispersion-strengthening and matrix grain refining and increased with the increase of incorporated Si₃N₄ particle content. The corrosion potential (E _corr) in the case of Ni–Si₃N₄ nanocomposite had shown a negative shift, confirming the cathodic protective nature of the coating.     

Characterizations of electrodeposited Ni–CeO2 nanocomposite coatings

The expansion of current machinery requires metallic materials with better surface properties. In the present investigation, CeO₂ reinforced nickel nanocomposite coatings were deposited on mild steel substrate by direct current electrodeposition process employing nickel acetate bath. The effect of incorporation of CeO₂ particles in the Ni nanocomposite coatings on the micro hardness and corrosion behaviour has been evaluated. Smooth and compact nanocomposite deposits containing well-distributed cerium oxide particles were obtained. The crystallite structure was fcc for electrodeposited nickel and Ni–CeO₂ nanocomposite coatings. It has been observed that, the presence of CeO₂ nanoparticles favours the [111] and [200] texture of nickel matrix. The co-deposition of CeO₂ nanoparticles with nickel was found to be favoured at applied current density of 8 A dm⁻². The micro hardness values of the nickel nanocomposite coatings (725 HV) was higher than that of pure nickel (265 HV).The decrease in I_corr values and increase in Constant Phase Element values were investigated in 3.5% NaCl solution which showed the higher corrosion resistant nature of Ni–CeO₂ coatings.     

双向脉冲快速电沉积非晶态Ni-P/Al_2O_3复合镀层

采用双向脉冲电沉积法制备出高P非晶态Ni-P/Al_2O_3复合镀层,利用扫描电镜(SEM)和能谱分析(EDS)方法考察镀层的微观形貌和化学组成,采用X射线衍射技术(XRD)表征镀层的相结构,并通过分析金属镀层和复合镀层的电化学测试结果,评价不同种类镀层的耐腐蚀能力。结果表明:与直流电沉积法相比,双向脉冲电沉积法可将镀层中的P含量提高至12.06%(质量分数),有利于非晶态Ni-P合金镀层的形成。采用双向脉冲法制备的Ni-P/Al_2O_3复合镀层比直流电沉积法制备的Ni-P/Al_2O_3复合镀层更平整、结晶更致密。脉冲电沉积法制备的非晶态Ni-P合金镀层具有更好的耐蚀性,而且复合微粒Al_2O_3的加入,对进一步提高非晶态Ni-P合金镀层的耐蚀性有积极作用。     

Corrosion and wear behaviour of multilayer pulse electrodeposited Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocomposite coatings assisted with ultrasound

In this study, the Ni–Al₂O₃ nanocomposite multilayer coatings with six consecutive layers were electrodeposited on the mild steel by pulse electrodeposition with ultrasound agitation from nickel Watts-type bath. The structure and morphology of the etched coatings cross-section were characterized by scanning electron microscopy (SEM). The corrosion behaviour of these coatings was investigated in 1 M H₂SO₄ solution. All of the coatings showed the active–passive transition and the distinct difference in structure had negative influence on their corrosion resistance. Moreover, the tribological behaviour of these coatings was evaluated by pin-on-disc type. The results showed that wear resistance increased with increase in duty cycle and frequency.     

Pulse and direct electrodeposition of Ni–Co/micro and nanosized SiO2 particles

Ni–Co/SiO₂ composite coating was electrodeposited on the steel substrate. The coatings were characterized by X-ray diffraction and scanning electron microscopy. The microhardness of the composite coatings was studied by variation of the electroplating parameters, such as the pulse current (PC) and direct current (DC) electrodeposition methods, deposition temperature, electrolyte pH, concentration of surfactants, sodium dodecyl sulfate (SDS), and cetyltrimethylammonium bromide (CTAB). Zeta potential of SiO₂ particles measurements was performed with various pH, SDS, and CTAB concentrations. The data depict that the hardness of Ni–Co/SiO₂ nanocomposite coatings manufactured by PC electrodeposition increases with the increase of bath temperature, pH, SDS, and CTAB concentration up to 50°C, 4.6, 0.3, and 0.2?g/L, respectively. Beyond mentioned optimum values, the microhardness of nanocomposite coating decreases. Using DC method led to reduce the microhardness. Utilizing SiO₂ microparticles instead of SiO₂ nanoparticles for reinforcing resulted in declining the microhardness. The friction coefficient and wear results demonstrated that using PC method and nanosized particles led to reduce the friction coefficient and increase the resistance to wear. Anodic polarization results illustrated that using SiO₂ nanoparticles and PC method to prepare coating caused corrosion resistance of coating in a 3.5?wt% NaCl solution to enhance.     

Silicate-based Plasma Electrolytic Oxidation (PEO) coatings with incorporated CeO2 particles on AM50 magnesium alloy

Plasma Electrolytic Oxidation (PEO) coatings on AM50 were developed in electrolytes containing CeO₂ particles. The effect of particle concentration in the electrolyte on the final microstructure of the coatings was studied and correlated with the corrosion behavior. CeO₂ particles were incorporated into the coatings and located preferentially in pores and cracks. The process involves both uptake and reactive incorporation of CeO₂ under local melting caused by microdischarges.The coating with the lower concentration of particles has the best corrosion properties as measured with EIS. Higher concentration of particles increased the defect density in the coating which has a negative effect on the corrosion resistance.     

Effect of CeO2 on the microstructure and isothermal oxidation of Ni-Al alloy coatings transformed from electrodeposited Ni-Al films at 800 °C

The electrodeposited two-phase γ-Ni + γ′-Ni₃Al and single-phase γ′-Ni₃Al coatings with and without CeO₂ particles were developed by the conversion of electrodeposited Ni-Al or Ni-Al-CeO₂ films with dispersed Al microparticles in Ni matrix into γ′-Ni₃Al by vacuum annealing at 800 °C for 3 h. SEM/EDAX and TEM characterizations showed that the CeO₂-dispersed γ-Ni + γ′-Ni₃Al or γ′-Ni₃Al coatings exhibited finer grains compared to the CeO₂-free Ni-Al alloy coatings. The oxidation at 1000 °C for 20 h showed that for a given Al content the addition of CeO₂ significantly improved the oxidation resistance of the electrodeposited Ni-Al alloy coatings. The effect of CeO₂ particles on the microstructure and oxidation behavior of the electrodeposited Ni-Al alloy coating is discussed in detail.     

Influence of duty cycle on the microstructure and microhardness of pulse electrodeposited Ni–CeO2 nanocomposite coating

The Ni–CeO₂ nanocomposite coatings have been synthesized by pulse electrodeposition technique with different duty cycles (6, 9 and 17%) from a Watts-type electrolyte containing nano-sized CeO₂ particles. The XRD results show that the (2 0 0) orientation is dominant over (1 1 1) orientation in the Ni–CeO₂ nanocomposite coatings prepared with 6 and 17% duty cycles, while the opposite is true for the sample prepared with 9% duty cycle. The maximum amount of CeO₂ (10 wt%) incorporation in the coating occurs at 9% duty cycle. The crystallite size changes from micrometer to nanometer as the duty cycle changes from 6 to 9%. The hardness increases as the duty cycle increases from 6 to 17%. However, a coating with optimum smoothness and small number of microcracks is obtained at 9% duty cycle.     

Oxidation behavior of aluminide coatings on carbon steel with and without electrodeposited Ni–CeO2 film by low-temperature pack cementation

A CeO₂-dispersed aluminide coating was fabricated through aluminizing the electrodeposited Ni–CeO₂ nanocomposite film on carbon steel using pack cementation method at 700 °C for 4 h. The isothermal and cyclic oxidation behavior of the CeO₂-dispersed aluminide coating at 900 °C, including the growth of oxide scale and the microstructure of the coatings, have been investigated comparing with the aluminide coating on carbon steel. The results show enhanced oxidation performance of the CeO₂-dispersed aluminide coating, which is concerned with not only CeO₂ effect on the microstructure and oxidation, but also decreased interdiffusion between the aluminide and the Ni film. The CeO₂ benefit effects and interdiffusion are discussed in detail.