镍-铁-磷/金刚石复合沉积工艺与性能研究

以三元合金为基体的复合电沉积层综合了一般耐磨镀层的性能和所镶嵌的固体微粒的性能.为开发新型多元非晶态合金耐磨复合沉积层,以复合沉积层耐磨减摩性为主要衡量指标并综合考虑其他性能指标,用正交试验法进行了镍-铁-磷/金刚石复合电沉积工艺与性能的研究.结果表明,在试验所采用的复合电沉积工艺控制范围内,可获得金刚石微粒弥散分布的镍-铁-磷/金刚石复合电沉积层,通过调整沉积工艺参数,能得到不同金刚石微粒复合量的复合电沉积层;在镀态下该复合沉积层(基质)呈非晶态结构;较佳综合性能复合层的电沉积工艺参数为:镀液中金刚石微粒(0.5～1.0 μm)含量6 g/L;NaH2PO2·H2O含量2 g/L;FeSO4·7H2O含量70 g/L,其对制备具有良好摩擦学特性的镍-铁-磷/金刚石复合沉积层具有重要的参考价值.     

非晶态Ni-W-WC复合镀层的制备及镀层性能研究

在非晶态Ni—W合金镀液中加入WC微粒，采用复合电沉积工艺制各非晶态Ni—W—WC复合镀层，井考察了复合镀层在碱性介质中的电催化析氢性能。结果表明，复合镀层中WC微粒的含量随镀液中WC微粒的浓度和电流密度的增加而增加；加入WC微粒后所获得的复合镀层仍然是非晶态结构；复合电板的电催化析氢性能明显优于Ni—W合金电板，性能的提高与其较高的比表面积和较低的析氢反应标准活化自由能有关。     

电沉积Co-Ni合金镀层结构及硬度的研究

采用氨基磺酸体系电解液电沉积Co-Ni合金，研究了电解液中钴、镍金属离子浓度与合金镍层中钴含量的关系。利用扫描电子显微镜和X射线衍射分析测定了不同钴含量沉积层的微观形貌和晶体结构，同时研究了合金沉积层显微硬度和合金成份的关系及热处理的影响。实验结果表明：电解液中Co^2 /(Co^2 Ni^2 ）在0.1-0.5的范围内时，钴离子的优先共沉积的趋势最强。SEM观察结果和XRD分析测试表明，随着钴镍合金沉积层中钴含量的不断增加，低钴含量合金层粗大的颗粒状结晶逐渐转变为细致、均匀的三角形状结晶，最终又形成中等大小的颗粒状结晶。同时合金层中钴含量的逐渐增加，结构由fcc镍固溶体过渡为fcc的钴固溶体，最后转变为hcp的钴固溶体。并且在形成两个钴固溶体的钴含量范围内（20％－50％和60％－80％），所对应的钴镍合金层的硬度值远大于低钴含量区所具有fcc镍固溶体结构的合金层硬度。     

（Ni—W）—WC复合镀层的研究

研究了Ｎｉ－Ｗ合金镀液中添加ＷＣ微粒制备（Ｎｉ－Ｗ）－ＷＣ复合镀层的电沉积过程，表征镀层的结构２和形貌，测试镀层在碱性溶液中的电催化氢析氧性能，探讨镀层的耐蚀性结果表明：（Ｎｉ－Ｗ）－ＷＣ为晶态复合镀层，析氢析氧性能优越，耐蚀性优良。     

电沉积Ni-W非晶态合金复合镀层研究

研究了在Ni－W非晶态合金镀液中加入ZrO2纳米微粒后的电沉积工艺,得到工艺参数与非晶态复合镀层的成分、结构和镀层在面形貌的关系。加入ZrO2纳米微粒后,提高了Ni-W非晶态复合镀层的高温抗氧化性能和硬度。     

低温熔盐电沉积羟基磷灰石复合涂层的研究

为了提高羟基磷灰石涂层的结合强度,在AlCl3-NaCl-TiCl3低温熔盐体系中加入HA微粒,复合电沉积制备Al-Ti/HA复合涂层,并对涂层的表面形貌、结构和结合强度进行了研究.结果表明: HA微粒均匀分散在Al-Ti合金镀层中,其共沉积量随电流密度的减小和熔盐中HA浓度的增大而增强;涂层的结合强度随HA共沉积量的增大而增强,当HA的共沉积量为40.1%(质量分数)时,Al-Ti/HA复合涂层的结合强度达到28.1 MPa.     

电沉积非晶Ni-Fe-P涂层析氢催化性能研究

采用直流电镀技术,通过改变电沉积电流密度制备了不同的非晶Ni-Fe-P涂层。采用稳态极化技术比较不同电流密度下电镀Ni-Fe-P合金涂层电化学催化析氢活性,发现电流密度200A/m2电沉积的Ni-Fe-P合金涂层的电化学催化析氢性能最好。通过XRD分析镀层相结构,SEM观察涂层表面的微观结构及EDX分析表面成分,研究影响非晶Ni-Fe-P合金涂层的析氢电催化活性原因。结果表明,影响非晶Ni-Fe-P合金涂层电催化活性的主要因素是镀层中Fe、P元素含量。当Fe的含量最大18.63%(原子分数),P的含量最小13.14%(原子分数)时,非晶Ni-Fe-P涂层电催化析氢活性最好。2     

纳米SiO2/Cu复合镀层的制备和组织性能研究

采用铜和纳米SiO2粉末的复合电沉积方法,在45钢板表面获得了厚度0.1～0.2 mm的Cu/SiO2 复合镀层,并应用扫描电镜、光学显微镜、显微硬度计、磨损试验机等对复合镀层的微观组织结构和性能进行了分析研究.结果表明:在实验进行的工艺范围内,可获得表面平整、光滑、 SiO2微粒均匀分布且与基体具有良好结合的复合电沉积层;复合镀层具有良好的硬度和耐磨性能;随镀覆时间的增加,复合镀层中的微粒粒度增加,并先沉积的粒子为核心而长大.     

Ni—ZrO2复合镀层的组织结构分析

采用复合电沉积技术制备Ｎｉ－ＺｒＯ２复合镀层，瘩在ＳＥＭ和ＴＥＭ上对其组织结构进行分析。与纯Ｎｉ镀层相比，复合镀层中ＺｒＯ２微粒的存在使基质金属Ｎｉ的晶粒显著细化，孪晶及位错密度均大幅度提高。     

喷射电沉积Co-Ni纳米合金沉积层的组织和性能

用高速喷射电沉积法快速制备了块体纳米晶Co-Ni合金,研究了喷镀工艺参数(主盐浓度、电解液喷射速度和电流密度等)对沉积层成分、微观组织结构及性能的影响.结果表明:提高喷射电沉积电解液的搅拌强度能有效减小扩散层的厚度,使电沉积在较高的极限电流密度下进行,提高沉积速度.极限电流密度的增大使阴极过电位增大,从而提高合金的形核速率,使沉积层晶粒的尺寸减小、显微硬度升高.随着电解液中Co2 含量的增加,沉积层中Co含量增加,导致沉积层相结构由单相α-Co(Ni)转变为α-Co(Ni)和ε-Co(Ni)双相组织,并使表面的形貌发生明显的变化.     

Advanced deposition characteristics of kinetic sprayed bronze/diamond composite by tailoring feedstock properties

In this study, the effect of protective nickel film on diamond particles was studied with the goal of preventing fracture and obtaining a uniform diamond distribution in a bronze/diamond composite coating during kinetic spraying. Two types of bronze/diamond composite were deposited on aluminum substrate. For comparison with experimental results, the impact behavior between diamonds in the gas flow field was simulated by finite element analysis (using ABAQUS/Explicit 6.7-2). Size distribution and deposition efficiency of the diamond particles in the composite coatings were analyzed through scanning electron microscopy and image analysis methods. Diamond fracturing was avoided because the impact energy was mostly absorbed by the outer protective nickel film on the diamond particle during impact. The uniform distribution and deposition efficiency of diamond particles in the coating layer could also be achieved by tailoring the physical properties (density, size, etc.) of the feedstock.     

Effect of activators on the properties of nickel coated diamond composite powders

Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding wheels were then prepared from Ni-coated diamond composite powders with different activators. The microstructural characterizations of this composite powders were finally conducted by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, and the mechanical and tribological properties of as-prepared diamond grinding wheels were also measured. There are changes in microstructures and properties of the composite powders with activators. The activator concentration also has an influence on the morphologies and phase structures of the Ni coating on diamond particles.The composite powders with more compact coating of nickel can be prepared by adding 1 g dm~(-3) or more AgNO_3 as an activator to electrodeposit nickel on diamond. The mechanical and tribological properties of diamond grinding wheels were significantly improved when the coating phase structure of Ni crystal grew with(111) plane orientation on the surface of diamond particles. The wheels made from nickel coated diamond composite powders possessed the advantages of easy preparation and outstanding tribological properties. Therefore, Ni coated diamond composite powders exhibit a great potential to be extensively applied in diamond cutting and grinding tools.     

纳米金刚石复合镀层制备工艺的研究

纳米金刚石复合镀层具有金刚石和纳米颗粒的双重特性,应用前景广阔.采用复合电镀法制备了Ni-纳米金刚石复合镀层,考察了阴极电流密度、镀液pH值以及搅拌强度对纳米复合镀层显微硬度的影响,并分析了Ni-纳米金刚石复合镀层的共沉积过程.结果表明,选择适当的共沉积工艺参数,可以制备出同底材结合牢固,金刚石微粒弥散较均匀的高硬度纳米复合镀层,基质Ni中金刚石粒子的含量与镀面的机械俘获粒子的能力有关.     

Thermal properties of diamond/SiC/Al composites with high volume fractions

The diamond/SiC/Al composites with high volume fractions and a large ratio of diamond to SiC particle size (7.8:1) were fabricated by gas pressure infiltration. The results show that the fine SiC particles occupy efficiently the interstitial positions around coarse diamond particles; the main fracture mechanism of the composite is matrix ductile fracture, and diamond brittle fracture was observed which confirms a high interfacial bonding strength; the diamond/SiC/Al composites with 80% and 66.7% volume fraction of diamond in the reinforcement have the higher volume fraction in the reinforcement and lower coefficient of thermal expansion compared to the diamond/Al composite. Turner and Kerner models are not in good agreement with the experimental data for the composites based on reinforcement with two phases different in shape and component. When the effect of the coating layer considered, differential effective medium (DEM) model is confirmed a reliable model in designing a composite with a given thermal conductivity based on reinforcement with two phases different in size.     

Ni-金刚石复合涂层的结构优化及基础磨削性能

采用电沉积技术在304不锈钢基体上制备了Ni-金刚石复合涂层。通过金刚石掺入量、加厚镀时间优化了金刚石复合涂层结构,利用球-盘式摩擦磨损试验仪研究了优化后的金刚石复合涂层对不同材料偶件(GCr15、SiC、304不锈钢)的磨削性能。结果表明:金刚石掺入量为1.5g/L时,金刚石上砂均匀且密集;加厚镀15min时,金刚石埋入率约为2/3,附着强度较好,适合磨削加工;GCr15、SiC、304不锈钢3种材料偶件的磨损体积依次减小,分别为:0.353 76mm~3、0.315 90 mm~3、0.194 01 mm~3,金刚石复合涂层对GCr15有较好的磨削性能;金刚石复合涂层磨削GCr15、SiC、304不锈钢均发生了磨粒磨损,此外,GCr15还发生了微弱的化学磨损,不锈钢发生了较明显的化学磨损和粘着磨损。     

镍-金刚石复合镀工艺条件的优化

为进一步了解各因素对复合镀镍-金刚石的影响,采用正交试验方法对镍-金刚石复合电镀工艺进行了研究,探讨了金刚石浓度、分散剂用量、电流密度、搅拌速度、超声频率对镀层中金刚石含量、镀层显微硬度和厚度的影响,确定了最佳工艺条件,并利用扫描电镜、能谱仪和硬度测试仪测试了最佳工艺所得镀层的形貌和性能。结果表明:50 g/L金刚石,8%分散剂,电流密度8 A/dm2、搅拌速度70 r/min和超声频率80 kHz下,所得镀层中金刚石的平均含量可达63.13%,镀层硬度可达1 927 HV。     

Numerical investigation of the effect of interfacial thermal resistance upon the thermal conductivity of copper/diamond composites

Copper/diamond (Cu/D) composites are known for their applications in thermal management systems. This paper investigates the effect of interfacial thermal resistance (TR) upon the effective thermal conductivity of Cu/D composites through experimental and numerical means. The composite samples were made using uncoated, Cu-coated, and Cr-coated diamond particles. The transient plane source method was used to measure the thermal conductivity of the composite samples, while the micrographs of the specimens were used to develop the finite element models. Together with the experimental and numerical results, the interfacial TR was identified in each sample. Although Hasselman–Johnson model calculated the conductivity values with significant error, the trend shown by experimental results is still followed. The finite element model, however, led to an error of less than 1%. The numerical analysis showed that the TR depends not only upon the diamond volume fraction but also upon the coating material. Finally, it has been demonstrated that numerical simulation may be employed to reveal the appropriate combinations of diamond fraction and the coating material in order to attain the desired level of effective thermal conductivity.     

Diamond formation on carbon/carbon composite

A carbon/carbon composite was used as substrate for low-pressure diamond deposition. To enhanced diamond nucleation on carbon/carbon composites, a total of ten surface preparation methods have been investigated. These methods involved the use of atomic hydrogen etching, mechanical polishing, sonication, or coating. Diamond nucleation was found to occur on either the defects of the carbon/carbon composite substrates or diamond particulate left on the substrates. The defects were created primarily by atomic hydrogen etching during the coating process. Seeding with diamond powders was performed by dip coating, sonication, or spray-coating processes. It was found that these seeding processes resulted in excellent nucleation of diamond.     

Diamond deposition on Mo with thermal stress buffer layer coated mild steel substrate by combustion flame CVD

In order to develop wear resistance diamond/molybdenum (Mo) hybrid coating process can be conducted in open air. Diamond deposition on the molybdenum with thermal stress buffer layer coated mild steel substrate by the combustion flame chemical vapor deposition (CFCVD) was carried out. As the thermal stress buffer layer, atmospheric plasma sprayed Mo/Fe mixture coating was deposited between Mo top coat and mild steel substrate. Consequently, crack generation and peeling off of the coating occurred due to thermal influences on the condition of Mo coated mild steel substrate in our previous study, diamond particles could be created on the Mo coating without fracture and peeling off. Besides, an additional Mo coating after diamond deposition increases the adhesion force between the diamond coating and the initial Mo coating. This encapsulation of the diamond particles between two Mo layers dramatically improves the resistance of the global coating making it strong enough to resist to the wearing test. These results demonstrate the high potential of thermal sprayed coating for the wear resistance improvement.     

电沉积参数对镍-纳米金刚石复合镀层性能的影响

目前有关纳米复合镀层电沉积的研究还不够深入、系统。以瓦特镀镍液为基础,在Q235A钢基体上制备镍-纳米金刚石复合镀层,研究了纳米金刚石浓度、搅拌速度对镍-纳米金刚石复合镀层性能的影响规律。在测试纳米金刚石复合镀液中镍的还原行为时发现,随着纳米金刚石浓度的升高,镍离子的极化程度呈现先升高后下降的趋势,镀液中纳米金刚石浓度为8.0 g/L时极化程度最大,同等条件下直流电沉积制备的复合镀层硬度、弹性模量分别为4.66 GPa和195.2 GPa,而双脉冲电沉积制备的镀层硬度和弹性模量分别达到5.23 GPa和197.4 GPa。