电沉积法制备纳米晶Ni-Co合金镀层

在氨基磺酸盐镀液体系中,采用电沉积法制备了纳米晶镍镀层和四种纳米晶Ni-Co合金镀层,采用FESEM、EDS和XRD表征了镀层的表面形貌、成分和晶体结构。结果表明,镍镀层和四种Ni-Co镀层的晶体结构都是简单面心立方结构;与镍镀层相比,Ni-Co合金镀层的平均晶粒尺寸减小,且当镀层钴含量为41.3%时,Ni-Co合金的平均晶粒尺寸最小为14.6 nm。在一定范围内,钴含量的增加有利于改善Ni-Co合金镀层的表面质量以及实现晶粒细化。     

脉冲电沉积钴镍合金层微观结构的研究

研究了钴镍合金镀液中Co^2 浓度与镀层中钴含量的关系,并采用XRD,TEM分析了不同钴含量合金镀层的微观结构。结果表明,沉积层中的钴含量随电解液中Co^ 浓度的增大而显著增大,当镀层中的钴含量为69．8％－78．9％（质量分数）时,镀层为面心立方晶格的α－Co相和排六晶格的ε－Co相组成;钴含量低于69．8％时为α－Co相,钴含量大于78．9％时为ε－Co相,钴含量增大,晶粒尺寸明显减小,合金点阵参数增大。     

镀液成份对锌铁合金化学和相组成的影响

通过对络合剂和添加剂进行筛选提出电镀光亮锌-铁合金的硫酸盐镀液及工艺条件,研究了镀液主要成份对合金沉积层的化学组成和相结构的影响.实验结果表明,沉积合金的含铁量主要取决于镀液的后Fe~(2+)/Zn~(2+)浓度比和柠檬酸的含量,聚乙二醇和胡椒醛的含量也略有影响.随着电沉积合金中含铁含量的提高,其相结构由低含铁量的六方密堆积η相向δ-相和体心立方的γ-相、面心立方的α-相转化.适当选择镀液各组份的配比,可在通常条件下电沉积出光亮范围宽,同基体结合好,含铁5～20%的Zn-Fe合金镀层.这种合金镀层可望在某些场合代替镍作为防护一装饰性的中间镀层.     

电沉积Ni—Co合金及其结构研究

采用硫酸盐体系电沉积Ｎｉ－Ｃｏ合金，研究了电镀工艺参数对镀层组成及电流效率的影响，测定了镀层结构。实验发现：在Ｎｉ－Ｃｏ合金镀层中，当Ｃｏ含量低于７６ｗｔ％时，合金由两种面心立方结构的固溶体组成；Ｃｏ含量介于７６￣９０ｗｔ％之间时，由面心立方和六方密排两种结构的固溶体组成；Ｃｏ含量超过９０ｗｔ％时，合金只有一种立方密排结构的固溶体相成。     

四硼酸钠对Ni-Co合金镀层的影响

为提高Ni-Co合金镀层硬度,采用单因素实验研究四硼酸钠对Ni-Co合金镀层硬度的影响,利用硬度测试考察Ni-Co合金镀层硬度的变化,采用金相显微镜对镀层微观形貌进行分析,通过X-射线衍射及能谱分析镀层的相组成和成分,采用电化学测试考察复合镀层耐蚀性。结果表明,当溶液中加入四硼酸钠时,Ni-Co合金镀层中的镍、钴发生变化,镍增加,钴减低,当四硼酸钠为15 g/L时镀层晶粒更加细致,外观表面更加光亮,镀层表面形貌达到最佳;腐蚀电流为9.422μA,硬度达到467.4 HV。     

工艺参数对电镀镍钴合金及其性能的影响

在氨基磺酸盐镀液体系中,采用电沉积法制备Ni-Co合金镀层,采用SEM、XRD与维氏硬度仪分析镀层相结构、微观形貌及显微硬度,并研究了沉积电流密度、氨基磺酸钴浓度及电镀液温度对镀层微观结构与显微硬度的影响.结果表明:阴极电流密度对镀层的择优取向无显著影响,但对各衍射峰强度影响较大.氨基磺酸钴浓度对择优取向有明显影响,当...     

脉冲镀Ni-Co合金镀层内应力及钴含量的研究

研究了脉冲镀Ni-Co合金的工艺,讨论了脉冲电镀中占空比及频率对镀层内应力及钴含量的影响.实验结果表明:镀层内应力随占空比的增加而降低,随脉冲峰值电流密度增加而升高,随温度的升高而降低.镀层中Co的质量分数则随温度的升高而升高.     

电沉积Ni－Co合金及其结构研究

采用硫酸盐体系电沉积Ｎｉ－Ｃｏ合金，研究了电镀工艺参数对镀层组成及电流效率的影响，测定了镀层结构。实验发现：在Ｎｉ－Ｃｏ合金镀层中，当Ｃｏ含量低于７６ｗｔ％时，合金由两种面心立方结构的固溶体组成；Ｃｏ含量介于７６～９０ｗｔ％之间时，由面心立方和六方密排两种结构的固溶体组成；Ｃｏ含量超过９０ｗｔ％时，合金只由一种六方密排结构的固溶体相成。     

高频脉冲镀Ni-Co合金的形貌、微观结构及耐蚀性研究

研究了紫铜基体上采用高频(20~140kHz)脉冲电流获得的Ni–Co合金镀层在w=10%的NaOH溶液中的耐蚀性。采用扫描电镜观察了碱蚀前后Ni–Co合金镀层的表面形貌,并测定了镀层在w=10%的NaOH溶液中的阳极极化曲线。结果表明,脉冲条件下所得的镀层致密,均匀,呈胞状生长,对w=10%的NaOH溶液有较强的耐蚀性。采用X射线衍射,分析了Ni–Co合金镀层的微观结构。当镀层中钴含量较低时,合金由面心立方结构的固溶体组成。随着脉冲频率的升高,Ni–Co合金镀层中的Co含量不断增加,其耐蚀性则不断降低。     

电沉积梯度Ni-Co纳米合金镀层的研究

采用直流电沉积技术制备了梯度Ni-Co纳米合金厚镀层。测定了该镀层的内应力及显微硬度,采用X射线衍射仪及能谱仪分别对镀层的晶相结构与成分进行了分析,采用扫描电镜对镀层的表面形貌和磨痕进行了观察,并对其摩擦、磨损性能进行了研究。结果表明,该合金镀层具有较好的成分梯度和相应的结构梯度,具有优异的抗磨减摩性能。说明梯度化的设计可以有效降低合金镀层的内应力,提高镀层的抗磨和减摩性能。     

High-speed jet electrodeposition and microstructure of nanocrystalline Ni-Co alloys

The jet electrodeposition from watts baths with a device of electrolyte jet was carried out to prepare nano-crystalline cobalt-nickel alloys. The influence of the concentration of Co²⁺ ions in the electrolyte and electrolysis parameters, such as the cathodic current density, the temperature as well as the electrolyte jet speed, on the chemistry and microstructure of Ni-Co-deposit alloys were investigated. Experimental results indicated that increasing the Co²⁺ ions concentration in the bath, the electrolyte jet speed and decreasing of the cathodic current density and decrease of the electrolyte temperature all results in an increase of cobalt content in the alloy. Detailed microstructure changes upon the changes of alloy composition and experimental conditions were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD results show the Ni-Co solid solution was formed through the jet electrodeposition. Phase constitution of solid solution changes progressively under different electrolyte concentration. Alloys with low Co concentration exhibit single phase of face-centered cubic (fcc) structure; The Co concentration over 60.39 wt.%, the alloys are composed of face-centered cubic (fcc) phase and hexagonal close-packed (hcp) phase. Furthermore, the formation of the nanostructured Ni-Co alloy deposit is investigated. Increasing the Co²⁺ ions concentration in the bath, the cathodic current density, the electrolyte temperature and the electrolyte jet speed all result in the finer grains in the deposits. Additives such as saccharin in the electrolyte also favor the formation of the finer grains in the alloy deposits.     

The role of anion additives in the electrodeposition of nickel-cobalt alloys from sulfamate electrolyte

Nickel-cobalt alloys have been deposited from sulfamate electrolyte with acetate and citrate-anion additives and evaluated for structure and properties, such as microhardness, tensile strength, internal stress and high-temperature oxidation. XRD data show that at low Co content, the alloys exhibit face-centered cubic (fcc) growth orientations. Above 60% Co, the deposit is completely hexagonal close packed (hcp) with pronounced (100) and (110) lines. It seems likely that the Ni-Co deposits from typical sulfamate electrolyte at pH 5, as well as at current density higher than 5 A/dm², include metal hydroxides. This is followed by the formation of a more strained structure. The high-temperature oxidation rate of the Ni-Co coating from sulfamate electrolyte at pH 5 is twice that of the alloy deposited from the electrolyte with anion additives. We believe that, citrate complexes of Ni and Co, which are assumed to be involved in alloy deposition, eliminate the incorporation of hydroxides into the deposits and enable low-internal-stress coating. The anion-modified bath offers stability of structure and properties of the alloy over a wide range of acidity and current density.     

粘结剂对超音速火焰喷涂碳化钨涂层磨粒磨损性能的影响

采用超音速火焰喷涂(HVOF)工艺在35钢基体上制备了WC-10Ni涂层和WC-12Co涂层,研究了镍、钴这两种粘结剂对WC涂层的显微硬度、摩擦系数和抗磨粒磨损性能的影响,采用扫描电子显微镜观察涂层磨损前后的表面形貌,探讨了WC涂层的磨粒磨损机理。结果表明,以HVOF方法制备的2种WC涂层均有较高的显微硬度,WC-10Ni涂层和WC-12Co涂层与SiC砂纸摩擦副之间的干摩擦系数相差不大。2种涂层在低载荷下均有较好的抗磨粒磨损性能,但在较高载荷下WC-12Co涂层的抗磨性明显优于WC-10Ni涂层。2种涂层的磨粒磨损形式主要为均匀磨耗磨损,磨损机理以微切削和微剥落为主。WC-12Co涂层的磨损表面损伤较轻微,综合性能优于WC-10Ni涂层。     

Self-lubrication and wear-resistance mechanism of graphene-modified coatings

To reduce the friction coefficient of WC-17Co wear-resistant coatings, Graphene oxide were used to mix with WC-17Co powder. The SEM, EDS and Raman results were used to analyze the morphology and phase composition of graphene oxide in the powder and coating obtained by plasma spraying processes. The mechanical properties of the coatings were studied by using a microhardness tester and a universal testing machine. The friction and wear properties of the coatings were studied by using a UMT-2 friction and wear tester. The results show that among the pulverization processes, the spray granulation process can achieve a stronger and more uniform adhesion of graphene oxide on the surface of WC-17Co particles, and the graphene oxide content in the coating is higher. Graphene is still embedded in the coating as transparent, thin sheets. The bonding strength is approximately 63 MPa, the hardness is approximately 931 HV0.1, and the friction coefficient of the graphene oxide coating is reduced by approximately 22% compared to that of the coating without graphene. The formation of lubrication films in the micro-area improves the self-lubrication and antiwear effects.     

A study of biotribological behavior of DLC coatings and its influence to human serum albumin

Diamond-like carbon (DLC) coatings has been synthesized on NiTi alloy substrates by arc enhanced magnetic sputtering (AEMS) system using graphite targets. The tribological behavior indicates that the friction coefficient and wear rate of DLC coatings deposited on NiTi alloy substrates is relatively higher in ambient air than that in simulated body fluid (SBF). In human serum albumin (HSA) solution, though the friction coefficient is higher than that in SBF, but it has quite low wear rate. The Raman spectrum shows that the low friction coefficient of DLC coatings is due to the graphitization during sliding, and the degree of graphitization is relatively lower in both SBF and HSA solution than them in ambient air. The friction mechanism of DLC coatings at different environments is then proposed. On the other hand, the kinematic viscosity and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) measurements show that the DLC coatings cannot induce the thermal and mechanical denaturation of HSA during sliding.     

电沉积Ni-Co合金的研究

研究了氨基磷酸盐电沉积Ni-Co合金电解液组成及工艺条件对沉积层中Co含量的影响.并测定了Ni-Co合金沉积层中Co含量与Ni-Co与硬度的关系,以及影响Ni-Co合金沉积层内应力的因素.实验结果表明,将一定量的Co引入Ni沉积层,可以显著地提高其硬度;当在电解液中添加一定量的Ni-1添加剂后,能使Ni-Co合金沉积层的内应力为零.这些有益的实验结果为电铸加工使用寿命长、机械性能好的模具提供了一定的依据.     

Effects of carbon nanotube content on adhesion strength and wear and corrosion resistance of epoxy composite coatings on AA2024-T3

The effects of multiwalled carbon nanotube (MWCNT) content on the adhesion strength and wear and corrosion resistance of the epoxy composite coatings prepared on aluminum alloy (AA) 2024-T3 substrates were evaluated using atomic force microscopy (AFM), blister test, ball-on-disk micro-tribological test and electrochemical impedance spectroscopy (EIS). The adhesion strength of the epoxy composite coatings improved with increasing MWCNT content. Increased MWCNT content also decreased the friction coefficient and increased the wear resistance of the epoxy composite coatings due to improved solid lubricating and rolling effects of the MWCNTs and the improved load bearing capacity of the composite coatings. Finally, EIS indicated that increased MWCNT content increased the coating pore resistance due to a decreased porosity density, which resulted in an increase in the total impedance of the coated samples.     

纳米Nb粉对等离子弧喷焊铁基合金组织与耐磨性的影响

采用等离子弧喷焊技术在Q235表面制备未添加与分别添加1wt%, 3wt%和5wt%纳米Nb粉的铁基合金喷焊层。通过X射线衍射仪(XRD)、金相显微镜(OM)、扫描电镜(SEM)和能谱仪(EDS)对喷焊层的相组成、显微组织、微区成分及磨损形貌进行分析;利用维氏硬度仪和销盘磨损仪检测喷焊层截面硬度和表面耐磨性。结果表明,铁基喷焊层主要由α-Fe, γ-Fe和Cr7C3组成,添加纳米Nb粉后原位生成NbC相,且随Nb含量增至5wt%,出现了Cr23C6相。纳米Nb粉的加入使喷焊层组织中未转变的奥氏体增多,组织形貌由近等轴晶转变为树枝晶,并且添加5wt%纳米Nb粉的喷焊层组织发生明显细化。添加纳米Nb粉使喷焊层的硬度明显提高,其中添加1wt%和3wt%纳米Nb粉的喷焊层硬度均可达约766 HV0.3。纳米Nb粉的加入同时提高了喷焊层的耐磨性,磨损机制由黏着磨损变为磨粒磨损。     

Nanocrystalline Ni–Co alloy coatings: electrodeposition using horizontal electrodes and corrosion resistance

Nanocrystalline Ni–Co alloy coatings containing 0–45 wt% Co were electrodeposited using horizontal electrodes in a modified Watts bath. Different techniques including scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, microindentation, and potentiodynamic polarization were used to characterize the alloy coatings. Properties of the alloy coatings were investigated as a function of the cobalt ion concentration (Co²⁺) in the bath. It was observed that the alloy codeposition exhibits anomalous behavior. Co content in the alloy coatings increases with increasing Co²⁺ in the bath and with electrolyte agitation. Morphology and grain size of alloy coatings are greatly affected by Co content. By increasing Co content, surface morphology of the alloy coatings changes from pyramidal to spherical. Microhardness of the alloy coatings increases with increasing Co content mainly due to decreasing grain size that follows the Hall–Petch relation. In addition, Ni–17 wt% Co alloy exhibits better corrosion resistance compared to pure Ni and other Ni–Co alloy coatings. The higher corrosion resistance of Ni–17 wt% Co coating is discussed based on its phase structure, grain size, and preferred orientation.     

TiC/Ti3AlC2–Co plasma-sprayed coatings with excellent high-temperature tribological properties

In this work, TiC/Ti₃AlC₂–Co cermet coatings with varying amounts of Ti₃AlC₂ were deposited by atmospheric plasma spraying (APS) process and their wear-resistant properties were discussed. The friction coefficients and wear rates at high-temperatures were measured through a ball-on-disk type friction test at 600 °C. In addition, the corresponding wear mechanisms were elucidated through the observation of phase changes and surface microstructural evolution of the coatings. The results indicated that the as-prepared coatings consisted of TiC, Ti, TiO₂, Al₂O₃, Co and CoO phases, which were produced by the decomposition and oxidation of TiC and Ti₃AlC₂. Compared with other samples, the sample with 30 wt% Ti₃AlC₂ addition displayed the smallest friction coefficient and least wear rate. Its wear rate was about 1.26 times lower than that of reported TiC–Co cermet material and about 10 times lower than that of the typically used TiC–Ni cermet material, suggesting outstanding wear resistance at elevated temperature. The addition of Ti₃AlC₂ reduced the friction coefficient of the coating by producing more TiC and Al₂O₃ hard phases and a consequent reduction of coating porosity. When the amount of Ti₃AlC₂ in the coating was less than 30 wt%, the main wear mechanism was abrasive wear. As the content of Ti₃AlC₂ was increased in the coating, the wear mechanism changed from abrasive wear to adhesive wear and the wear pattern of the coating gradually transformed from the furrows to the debris. This transformation of mechanism was related to the synergistic effect of hardness and porosity of the coating, which resulted from the remaining content and the special layered structure of Ti₃AlC₂.