Q235钢表面Ni-Cr电镀层的组织及性能

为提高Q235钢的表面防护性能,对其进行表面电镀Ni-Cr处理,并采用正交试验对电镀Ni-Cr工艺进行优化。采用X射线衍射仪(XRD)、扫描电镜(SEM)和激光共聚焦显微镜(OM)分别对镀层进行物相表征和形貌观察,利用显微硬度计、磨粒磨损机和电化学工作站对镀层硬度和耐蚀性进行研究。结果表明:以镀层沉积速率为指标,正交试验所得电镀Ni-Cr优化工艺为柠檬酸钠含量30 g/L,镀液pH值3.0,电流密度20 A/dm~2,电镀温度35℃,镀层沉积速率可达40.17μm/h;Ni-Cr镀层相结构由γ-Ni和Cr_(1.22)Ni_(2.88)组成;镀层表面平整,表面形貌为密集球形颗粒;与基体相比,正交试验所得Ni-Cr镀层硬度提高了81.62~649.08 HV_(2N),磨损率减少了9.14~29.99mg/cm~2,自腐蚀电位提高了2.05~121.28 mV。     

电沉积Ni-Cr合金工艺研究

含有一定量Cr的Ni-Cr镀层具有良好的耐磨、耐腐蚀性能.选取柠檬酸钠作为配位剂,用动电位扫描法研究了电沉积Ni-Cr合金时的阴极行为,同时对镀层的耐腐蚀性进行了试验.试验结果表明:镀液中加入配位剂柠檬酸钠可以提高阴极极化;pH值、阴极电流密度、配位剂对镀层中铬含量影响较大,在一定范围内增大pH值,增加配位剂的用量,提高电流密度,有利于提高镀层中铬的含量,最佳工艺条件为pH值为2.5,阴极电流密度为25A/dm2,镀液中柠檬酸钠的含量为35g/L,镀层中铬质量分数为20%左右时,Ni-Cr合金镀层的耐腐蚀性能最好.     

Ni-Cr合金共沉积的电化学特性

通过线性扫描和循环伏安曲线分析,研究了柠檬酸溶液中Ni-cr合金共沉积的电化学特性,并采用扫描电镜(SEM)和X射线衍射(XRD)对镀层的表面形貌和结构进行了表征.结果表明,Cr3和Ni2 有相互促进放电、加速共沉积的作用.温度升高,阴极极化减小,Ni-Cr合金镀层中Cr含量下降;pH值适度增大,极化增大,镀层中Cr含量和电流效率增大;柠檬酸增大电流密度,促进Ni-Cr合金共沉积;光亮荆增大阴极极化,提高镀层光亮度;NaBr抑制Cr(Ⅵ)的生成,加速Ni-cr合金的共沉积;SEM表明Ni-Cr镀层表面光亮,由密集的球形颗粒组成,XRD表明镀层为面心立方(FCC)固溶体晶体结构.     

Ni-Cr合金在三价铬水溶液中的电沉积

Al基体上电镀Ni-Cr合金可以大幅度改善其防护性能,为此以铝为基体,以柠檬酸为配位体,在三价铬的硫酸盐-氯化物镀液中电沉积了光亮平滑、质量优良、与基体结合良好、Cr含量为1.4%～26.0%、厚度为10～30μm、最大电流效率可达58.0%的Ni-Cr合金镀层.研究了电流密度、温度、pH值、CrCl3浓度等参数对电流效率和镀层厚度的影响.电位滴定显示,镀液的缓冲能力良好;阴极极化曲线表明,Ni-Cr合金的电沉积符合Tafel方程.SEM形貌观察发现,Ni-Cr合金表面布满了均匀密集的球形小颗粒;通过XRD检测确定,Ni-Cr合金为晶体结构,Cr含量升高使晶粒变小;Ni-Cr镀层的耐蚀性较好,Cr含量的升高有利于耐蚀性的提高.     

碱性条件下Fe-P-B合金电镀

研究了碱性溶液中镀液组成、阴极电流密度、温度、pH值对Fe-P-B合金电镀层沉积速率和组成的影响,优化了工艺,在最佳工艺条件下获得Fe-P-B镀层,并对镀层的耐腐蚀性、结构和结合力进行了分析.结果表明:提高镀液中硫酸亚铁铵含量、溶液pH值、温度和电流密度,镀层沉积速率增加;提高镀液中次亚磷酸钠、丙二酸和硼氢化钠含量,镀层沉积速率先增后降低,出现一个极大值;镀层中B含量的增加会使P含量降低,但提高电流密度和镀液温度时二者都有所增加;在最佳工艺条件下获得的Fe-P-B合金镀层为非晶态结构,和基体结合力优良,耐蚀性良好,在15%NaoH溶液中的耐腐蚀性优于在5%NaCl溶液中.     

Cu对铝基化学镀Ni-Cu-P镀层耐蚀性能的影响

采用直接镀工艺,在铝基体上获得了化学镀N-P、Ni-Cu-P各种结构镀层.用X射线衍射分析了镀层结构;用SEM观察了各种结构镀层的表面形貌;测定了各种结构镀层的镀速和结合力;利用线性极化和阳极极化曲线分析了各种结构镀层的耐蚀性能.结果表明,利用直接化学镀工艺可以在铝基上获得结合力良好的镀层;通过控制络合剂的用量可以得到不同结构和不同铜含量的Ni-Cu-P镀层;当镀层达到一定厚度后,Cu元素可以显著提高镀层的耐蚀性能.     

化学镀Ni-Fe-P合金镀液组分及pH值对镀层性能的影响

目前,对化学镀Ni-Fe-P合金镀液影响镀层形成及其阴极极化曲线的研究较少。在纯铜片表面化学镀Ni-Fe-P合金;采用扫描电镜观察了镀层的形貌,采用能谱仪测试了镀层成分,采用X射线衍射仪分析镀层的结构,采用电化学工作站测试镀层在镀液中的阴极极化曲线;通过单因素法考察了镀液组分含量及pH值对化学镀Ni-Fe-P合金沉积速率、镀层成分、形貌、结构及阴极极化曲线的影响。结果表明:镀液各组分含量及pH值对镀层性能有较大影响;最佳工艺条件为20 g/L硫酸镍,12 g/L硫酸亚铁,30 g/L次磷酸钠,40 g/L柠檬酸三钠,20 g/L硫酸铵,20 mL/L乳酸,pH值9.0,镀液温度80℃,时间1 h;此条件下所得Ni-Fe-P合金镀层以非晶态形式存在,其耐蚀性能明显优于相同工艺条件制备的Ni-P镀层。     

工艺参数对Ni-SiC纳米镀层SiC粒子复合量的影响

采用超声波辅助电沉积方式,在45钢表面制备了Ni-SiC纳米复合镀层。根据阴极电流密度、PH值和搅拌速度对Ni-SiC纳米复合镀层SiC粒子复合量的影响,获取Ni-SiC纳米复合镀层最佳条件的工艺参数;并利用扫描电镜(SEM)、高分辨率透射电镜(HRTEM)研究工艺参数对Ni-SiC纳米复合镀层表面形貌和微观组织结构的影响。结果表明,获取Ni-SiC纳米复合镀层最佳工艺参数为阴极电流密度6A/dm~2,pH值=4,搅拌速度300r/min。由最佳工艺参数制得的Ni-SiC纳米复合镀层表面呈胞状,SiC粒子粒径尺寸较小,其平均粒径为21.5nm。     

AZ91D镁合金化学镀Ni-P工艺参数研究

通过正交试验研究了工艺参数对镁合金化学镀镍磷镀层性能的影响,获得了最佳镀覆条件,并考察了镀后热处理工艺.研究表明:在AZ91D镁合金表面化学镀镍磷合金可有效提高镁合金的表面硬度和耐蚀性,在最佳工艺条件下可获得表面平整致密、镀层与基体结合良好、具有银白金属光泽的镍磷镀层;热处理可使镀层硬度上升,但镀层的耐蚀性却下降,获得最优综合性能的热处理温度为340℃.     

脉冲电镀Zn-Ni合金工艺参数对镀层Ni含量及形貌的影响

为了优化Zn-Ni合金制备工艺,在硫酸盐型Zn-Ni合金镀液中脉冲电镀Zn-Ni合金层。分别采用扫描电镜和X射线成分分析镀层形貌和成分,通过中性盐雾试验测试镀层耐蚀性。研究了脉冲参数、工艺条件对Zn-Ni合金镀层Ni含量与形貌的影响。结果表明:镀液温度、平均电流密度、频率、逆向脉冲系数及占空比对镀层性能和形貌均有较大影响;最佳工艺参数为温度60℃,平均电流密度70 m A/cm2,脉冲频率200 Hz,逆向脉冲系数0.4,占空比0.7,此时Zn-Ni合金镀层晶粒细小,表面平整光亮,呈银白色,镀层Ni含量为13%,耐蚀性优良。     

Nickel-based,binary-composite electrocatalysts for the cathodes in the energy-efficient industrial production of hydrogen from alkaline-water electrolytic cells

Ni-Mo, Ni-Zn, Ni-Co, Ni-W, Ni-Cr and Ni-Fe, binary-composite, codeposit surface coatings on mild-steel substrates were prepared by conventional electrodeposition techniques. The chemical compositions and the micrographic surface features of these coatings are reported. The utility of these coatings as cathodes in laboratory-scale alkaline-water electrolytic cells was assessed by polarisation techniques. The trend in their electrocatalytic activities ranks in this order: Ni-Mo>Ni-Zn>Ni-Co>Ni-W>Ni-Fe>Ni-Cr. The electrocatalytic activity of these coatings is very significant when compared with the data on conventional mild-steel cathodes currently used in industry. The results obtained experimentally are presented. A brief discussion is also included to highlight their utility.     

Cr颗粒含量对Ni-Cr纳米复合镀层组织结构的影响

使用Ni与纳米Cr颗粒共沉积方法制备Ni-Cr纳米复合镀层,研究了镀液中Cr颗粒浓度、搅拌强度和阴极电流密度等工艺参数对镀层中沉积Cr量的影响.结果表明:镀层中纳米Cr颗粒的复合改变了电沉积Ni的生长方向,Ni晶粒由原来沿(200)晶面取向生长,转变为沿(200)、(111)和(220)晶面均匀生长.镀层中Cr复合量越多,Ni晶粒的形核位置越多,Ni晶粒越细化.也探讨了Ni-Cr纳米复合镀的沉积机理.     

冷喷涂Zn粉后5083铝合金的中温钎焊研究

以添加了5%(质量分数,下同)CsF-AlF3共晶钎剂的Zn粉为原料,采用冷喷涂技术在5083铝合金表面制备涂层,喷涂后的5083铝板在530℃进行钎焊连接。采用扫描电子显微镜结合能谱仪对涂层的显微结构及钎焊后的接头组织形貌进行观察与分析。结果表明:涂层与5083基体连接致密,钎剂颗粒呈絮状存在于Zn粒子交界面处;由于涂层对5083基体的保护,钎焊时5083基体表面没有出现Mg元素上浮现象,表面未形成复杂的氧化膜,530℃喷涂后的5083与1060可成功实现连接;钎焊接头组织均匀,主要由α铝基固溶体和β富锌基固溶体组成,存在少量孔洞缺陷。     

2219铝合金搅拌摩擦焊接头微观组织对微弧氧化膜生长的影响

采用微弧氧化方法在硅酸盐电解液里在2219铝合金搅拌摩擦焊接头表面均匀生长一层50 μm陶瓷膜, 分析了铝合金基体和焊缝区陶瓷膜的形貌、相组成和显微硬度分布, 探讨了合金显微组织和微弧氧化膜生长过程的相互影响. 结果表明, 铝合金显微组织对微弧氧化膜的生长影响较小, 铝合金基体和焊缝区的微弧氧化膜特性几乎相同, 陶瓷膜都是由α-Al₂O₃、γ-Al₂O₃和莫来石(3Al₂O₃·2SiO₂)相组成; 不同区域膜层的显微硬度相等, 其平均硬度约为HV 1500. 另外, 微弧放电高温过程对膜/基界面附近的铝合金显微组织没有影响.     

Ti-Al双丝超音速电弧喷涂涂层的滑动磨损特性研究

为了提高铝合金(LY12)的表面耐磨性,采用钛、铝金属丝材和SAS-Ⅰ型超音速电弧喷涂设备,利用二次回归正交试验方法、有润滑滑动磨损试验、涂层显微组织和磨损表面形貌观察、XRD分析,定量分析了喷涂电压和喷涂距离对涂层滑动磨损体积的影响规律,并进行了喷涂工艺参数的优化及其与基体滑动磨损的对比试验.结果表明:在特定的磨损和喷涂条件下,当喷涂距离较小时,随喷涂电压的增大,涂层的体积磨损量逐渐减小;随着喷涂距离的增加,涂层的体积磨损量随喷涂电压的升高逐渐增大,并且喷涂距离越大,涂层的体积磨损量随喷涂电压增大的速率愈大.当喷涂电压比较低时,涂层的体积磨损量随喷涂距离的增大而降低,但是,随喷涂电压的逐渐升高,涂层的体积磨损量随喷涂距离的增大逐渐上升,并且,喷涂电压愈高,其随喷涂距离而增加的速率越快.当喷涂电压和喷涂距离分别为26V和0 236m时,涂层具有最佳的耐滑动磨损性能,根据该工艺参数制成的涂层,其滑动磨损体积仅为LY12铝合金的1/38.84.即在适当的工艺条件下,Ti-Al双丝超音速电弧喷涂涂层对LY12铝合金具有显著的表面耐磨强化作用.     

Preparation of Ni–Co alloy coating on sintered NdFeB magnet by potentiodynamic electrodeposition

A protective Ni–Co alloy coating was successfully prepared on sintered neodymium–iron–boron (NdFeB) magnet via potentiodynamic electrodeposition in this paper. The microstructure and surface morphology analysis of Ni–Co alloy coating showed that the surface morphologies were quite compact and more uniform than that prepared by direct current (DC) electrodeposition; significantly, the chemical composition analysis indicated that the content of Co in the alloy coatings amounted to 33–34?wt-%. Potentiodynamic polarisation and long term immersion test results revealed that the Ni–Co alloy coating could supply excellent corrosion protection for NdFeB substrate in 3.5?wt-% NaCl solution. Overall, the Ni–Co alloy coating with higher Co content prepared by potentiodynamic electrodeposition exhibited better corrosion protection for sintered NdFeB magnet compared with that prepared by DC electrodeposition.     

Microstructure and tribological property of nanocrystalline Co–W alloy coating produced by dual-pulse electrodeposition

The nanocrystalline Co–W alloy coatings were produced by dual-pulse electrodeposition from aqueous bath with cobalt sulfate and sodium tungstate (Na₂WO₄). Influence of the current density and Na₂WO₄ concentration in bath on the microstructure, morphology and hardness of the Co–W alloy coatings were investigated using an X-ray diffraction, a scanning electronic microscope and a Vickers hardness tester, respectively. In addition, the friction and wear properties of the Co–W alloy coating electrodeposited under different condition were evaluated with a ball-on-disk UMT-3MT tribometer. The correlation between the electrodeposition condition, the microstructure and alloy composition, and the hardness and tribological properties of the deposited Co–W alloy coatings were discussed in detail. The results showed that the microhardness of the deposited Co–W alloy coating was significantly affected by its average grain size, W content and crystal orientation. Smaller grain size, higher W content and strong hcp (1 0 0) orientation favor the improvement of the hardness for Co–W alloy coatings. The deposited Co–W alloy coating could obtain the maximum microhardness over 1000 kgf mm⁻² by careful control of the electrodeposition conditions. The tribological properties of the electrodeposited Co–W alloy coating were greatly affected by its grain size, microhardness, surface morphologies and composition, and could be significantly improved by optimizing the electrodeposition condition.     

LY12铝合金铈化学转化膜的结构及耐蚀性研究

应用电化学方法及腐蚀试验研究了LY12铝合金表面常温稀土化学转化膜。结果表明，铝合金的稀土化学转化膜具有成膜温度低、速度较快、膜的耐蚀性能好等优点。电位－时间曲线表面，成膜动力学包括铝合金的溶解及随后的成膜两个过程。SEM表明，铝合金稀土化学转化膜的形态为片状，EDAX能谱表明转化膜主要由Ce,O,Al及少量的促进剂离子组成。腐蚀试验表明，未经处理的铝合金在3．5%NaCl溶液中经过21天浸泡后，表面出现了严重的点蚀，而经稀土处理的铝合金经过相同时间的浸泡后，表面只发生了轻微的均匀腐蚀，而未发生点蚀，浸泡后稀土处理的铝合金的失重较空白试样的下降了近1倍，铝合金的耐蚀性能大大提高。     

铝合金表面超疏水涂层的火焰喷雾热解法制备及其耐蚀性能

采用火焰喷雾热解与表面修饰相结合的方法在铝合金表面制备了具有一定耐蚀性能的超疏水表面。以六甲基二硅氧烷溶液为前驱液,通过火焰喷雾热解方法,首先在铝合金表面沉积SiO2纳米颗粒构建粗糙结构,再以氟硅烷溶液进行表面修饰,获得了具有154.9°静态接触角,滚动角<2°的超疏水表面。通过电化学测试,对比了构筑超疏水表面前后的铝合金样品的耐蚀性能。结果表明沉积层与低表面能物质协同作用,通过对腐蚀性离子的有效隔离,提高了铝合金基体的耐蚀性能。     

Properties of evaporated Ni-Cr films with an aluminum content of about 50%

Films with an aluminum content of about 50% in Ni-Cr were produced as a continuation of investigations on multicomponent thin alloy films based on Ni-Cr, because an additional zero transition for the temperature coefficient of resistance (TCR) of these thin films was indicated in the earlier investigations. The alloy films were evaporated in high vacuum onto ceramic substrates and measurements of the TCR and the stability were carried out. It was found that the TCR is less than ±50 ppm K^-1 for aluminum concentrations between 45 and 65 at.%. Such films are suitable for the production of metal film resistors.