汽车减振器连杆快速镀铬吸氢与耐腐蚀性能研究

汽车减振器连杆电镀工艺决定了其镀铬层的质量及其耐腐蚀性能,连杆耐蚀性是影响减振器寿命的主要因素之一.快速镀铬与普通镀铬工艺相比,在高的电流密度条件下具有高电流效率.连杆镀铬时,不同电流密度则饺层渗氢量不同,决定镀层组织及内应力也不同.在JEEF25工艺条件下,通过理论计算得到了减振器连杆不同电流密度的铬层氢含量,取得了电流密度优化参数.研究结果为优化企业的电镀生产工艺、提高汽车减振器的制造水平提供了依据.     

基于正交试验设计与人工神经网络优化镀铬工艺

提出了一种正交试验设计与人工神经网络相结合的镀铬工艺参数优化方法。样本极差结果表明,对镀铬层的厚度及阴极电流效率影响因素依次为电流密度、电镀时间、电镀温度;且最佳电镀温度为45℃。通过神经网络建立电镀工艺参数与性能之间的模型,预测得出的镀铬层的厚度和阴极电流效率与实际试验的结果接近,训练精度较高,预测值与试验值的相对误差小于1.20%。通过建立镀铬层多指标综合评价模型,对镀铬层的厚度及阴极电流效率两个指标进行综合评价,通过对两个指标权重值的调整,确定镀铬层的综合性能值,得出最优的工艺参数。     

电流密度对镀铬钢板表面特性的影响

电镀工艺对镀铬钢板的性能具有决定性影响.通过电化学试验、热振试验、X射线光电子能谱(XPS)以及扫描电镜(SEM)等,研究了电流密度对镀铬低碳钢板耐蚀性、镀铬层组成及其与有机膜结合力的影响.结果表明:电流密度过大将加剧铬及其氧化物和氢氧化物在基板的沉积,镀铬板的耐蚀性能较差.以5 A/dm2的电流密度镀铬的低碳钢板的耐...     

高耐蚀性镀硬铬工艺研究

针对空客生产的A320机型合金钢零件镀硬铬层高耐腐蚀性的要求,研究了一种高耐蚀性镀硬铬工艺,所获得的镀铬层硬度为750～980HV,并且通过了750h的盐雾试验,满足空客技术要求。研究还发现,特殊的电镀硬铬工艺,尤其是镀铬后的HA油除氢、磨削等是提高硬铬镀层耐腐蚀性能的关键。该工艺目前已在工厂的批量生产中获得应用。     

基体镀前表面状态对镀铬层综合性能的影响

电镀前对工件抛光处理,在碳钢表面电镀硬铬,考察镀前阳极刻蚀对不同粗糙度基体镀铬层耐蚀性能的影响,通过分析镀层的厚度、硬度、孔隙率和镀层耐盐雾试验能力来表征镀层综合性能。实验结果表明:碳钢基体粗糙度在小于0.20μm且经阳极刻蚀的条件下,硬铬镀层的综合性能满足工艺要求,具有良好的耐蚀性,可达到NSS200h10级水平。     

高电流密度电镀锌对钢板耐蚀性的影响

通过塔菲尔曲线的测量,研究了高密度电流(300 A/dm2)下镀层的耐蚀性。结果表明:采用高电流密度进行电镀,其电镀层的腐蚀电位随电流密度的增大而提高(最高可达-0.845 V),腐蚀速率降低,耐蚀性增强;并且分析了高电流密度对镀层微观形貌的影响。     

产品介绍

随着对电镀产品耐腐蚀性的要求越来越高,原有的氰化物镀锌层耐蚀性就很难达到要求,而在低氰,中、高氰镀锌液中加入该添加剂均可以使镀锌层耐蚀性大幅度提高,外观光亮也得到提高。某航空厂使用该添加剂前镀锌层彩钝化后盐雾试验72h就发生腐蚀,而加入该添加剂后,盐雾试验可达124 h以上。添加剂使用量为10～20m,原来的镀锌工艺条件不变,     

Q235钢表面熔盐电镀铝及其耐蚀性的研究

将Q235钢试样分别经150℃的AlCl3-NaCl-KCl熔盐和800℃的Al和NaCl-KCl熔盐处理后,可在试样表面获得电镀铝层。对电镀铝层的耐蚀性进行了研究,结果表明,无论是低温电镀还是高温电镀,电镀铝层的厚度都随电流密度的增大和电镀时间的延长而增加,镀层厚度和电镀时问的平方根呈线性关系,而且其耐蚀性得到显著的提高。     

镁合金微弧氧化陶瓷层耐蚀性的研究

利用盐雾腐蚀试验和SEM等分析手段，研究了镁合金微弧氧化陶瓷层的腐蚀过程及4各电解液体系对陶瓷层耐蚀性的影响，分析了镁合金微弧氧化陶瓷层与铬化处理膜层耐蚀性的差异和封孔处理的作用机理，结果表明，在复合系电解液中处理的镁合金样品耐蚀性最好，所有微弧氧化处理的样品其耐蚀性均远优于铬化处理样品，用石蜡孔可明显提高样品的耐蚀性。     

镁合金化学镀电镀复合镀层的制备

镁合金具有高的比强度和比刚度、电磁屏蔽性、减震性等优点,广泛应用于航空航天、汽车、电子通讯等领域.然而,由于镁合金的化学活性较高,其耐蚀性能较差,限制了它们的应用.通过改进的镁合金加工工艺可以提高镁合金耐蚀性.另外1种提高镁合金耐蚀性的有效手段就是对镁合金进行表面处理,如化学转化膜、电镀等.这些处理得到的涂层耐蚀性虽然有了很大的提高,但是在长时间处于腐蚀环境中,也容易被腐蚀,因此,研究1种复合镀层来更进一步提高耐蚀性,可以提高镁合金的应用.通过采用以硫酸镍为主盐对镀层进行化学镀镍,在化学镀层基础上电镀锌镍合金,并对化学镀和电镀配方进行优化,得到的复合镀层硬度高、结构致密、光泽性好,在5%的NaCl溶液盐雾试验中,连续喷雾96h无任何腐蚀现象,耐蚀性得到显著的提高.     

In-situ analysis of inner crack instability of electro-deposited trivalent chromium layers using small angle neutron scattering

Inner crack behavior of electro-deposited trivalent chromium was analyzed in-situ by small angle neutron scattering to study the abrasive heating effect on neutral salt fog spray life. The trivalent chromium was prepared by different current wave forms, namely, direct and pulse current-plating with a modified chromium chloride bath. The trivalent chromium layer has columnar grains in which small chromium clusters and inner cracks are present. Pulse current plated trivalent chromium has a longer neutral salt fog spray life than direct current plated trivalent chromium. As surface temperature increases to 80 °C, inner cracks of the trivalent chromium layer formed by direct current plating tend to have a fractal shape by opening crack tips, whereas those of the chromium layer formed by pulse current plating are relatively stable. The inner crack with a fractal shape is related to an abrupt reduction of the neutral salt fog spray life of the trivalent chromium.     

Electro-deposition behaviors of trivalent chromium during pulse plating

Thick trivalent chromium layers were prepared in a modified chromium sulfate bath by pulse plating to replace hexavalent hard chromium coating in industrial fields; layer microstructure development was systematically studied by using electron microscopy and small angle neutron scattering (SANS) to give a model for nucleation and growth behaviors during the pulse plating. Finer columnar grain was formed by pulse plating due to its high nucleation rate at the same current density. Average deposition rate of the trivalent chromium layers is in the range of 32.4 μm/h to 49.7 μm/h. The deposition rate increases as the diameter of cylindrical shape of chromium cluster in a columnar grain is reduced. The highest deposition rate in this study was observed under the conditions of direct current density of 0.4 Acm⁻², combined with a rectangular shape pulse current density of 1.5 Acm⁻² with a 10/2 on-off time ratio. Most of the inner-cracks of the trivalent chromium layers have dimensions in the range of about 39 nm. Ultrasonic agitation during pulse plating resulted in an increase of neutral salt fog spray life, which is related to smaller crack size and broader size distribution in the trivalent chromium.     

A new method for electroless Ni-P plating on AZ31 magnesium alloy

Coating Ni-P films on AZ31 magnesium alloys via electroless plating and organic coatings (organsilicon heat-resisting varnish), was studied. An organic coating was proposed as the interlayer between Ni-P coating and AZ31magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The Ni-P deposited on the interlayer was also characterized by its structure, morphology and corrosion-resistance. The interlayer on the substrate not only reduces the corrosion of magnesium during Ni-P plating process, but also reduces the potential difference between the matrix and the second phase. The result of the cross-cut test indicates the adhesion between the substrate and the interlayer is good enough. A Ni-P film with fine and dense structure was obtained on the AZ31 magnesium alloy. The electrochemical measurements show that the sample with Ni-P film exhibits lower corrosion current density and more positive corrosion potential than the substrate. Furthermore, the Ni-P coating on the AZ31 magnesium alloy exhibits high corrosion resistance in the rapid corrosion test illustrated in this paper. The method proposed in this work is environmentally friendly: no fluoride or hexacalent chromium compounds are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity.     

锌镍合金镀工艺优化及镀层耐腐蚀性的研究

目的研究锌镍合金镀层的耐腐蚀性能。方法通过正交试验法,对锌镍合金电镀工艺进行优化,获得镀液配方。通过中性盐雾试验评判优化后的锌镍合金镀层的耐腐蚀性能,并与镀锌层和镀镉层进行对比。分析主盐、络合剂、p H值、电流密度、温度等对镀层耐腐蚀性的影响。结果最优配方为:氧化锌6~14 g/L,硫酸镍20~30 g/L,氢氧化钠100~140 g/L,光亮剂4~6 g/L,络合剂50~70 g/L。该配方获得的锌镍合金镀层在中性盐雾实验中,出白锈的时间可以达到720 h以上。结论锌镍合金镀层的耐腐蚀性优良,优于镀锌层和镀镉层。     

Evaluation of WC–17Co and WC–10Co–4Cr thermal spray coatings by HVOF on the fatigue and corrosion strength of AISI 4340 steel

It is known that chromium electroplating is related to the reduction in the fatigue strength of base metal. However, chromium results in protection against wear and corrosion combined with chemical resistance and good lubricity. Environmental requirements are an important point to be considered in the search for possible alternatives to hard chrome plating. Aircraft landing gear manufactures are considering WC thermal spray coating applied by the high-velocity oxygen-fuel (HVOF) process an alternative candidate, which shows performance at least comparable to results, obtained for hard chrome plating. The aim of this study is to compare the influence of WC–17Co and WC–10Co–4Cr coatings applied by HVOF process and hard chromium electroplating on the fatigue strength of AISI 4340 steel, with and without shot peening. S–N curves were obtained in axial fatigue test for base material, chromium plated and tungsten carbide coated specimens. Tungsten carbide thermal spray coating results in higher fatigue strength when compared to hard chromium electroplated. Shot peening prior to thermal spraying showed to be an excellent alternative to increase fatigue strength of AISI 4340 steel. Experimental data showed higher axial fatigue and corrosion resistance in salt fog exposure for samples WC–10Co–4Cr HVOF coated when compared with WC–17Co. Fracture surface analysis by scanning electron microscopy (SEM) indicated the existence of a uniform coverage of nearly all substrates.     

汽车减震器活塞杆断裂失效分析

通过光学显微镜、扫描电子显微镜和能谱仪等分析手段,对汽车减震器活塞杆压弯检验过程中的异常断裂原因进行了分析。结果表明,活塞杆表面镀Cr层厚度约为24 μm,次表层淬硬层深度约为0.8 mm,次表层组织为回火马氏体+少量铁素体,心部基材组织为铁素体+珠光体;压弯试验时,活塞杆首先在最大弯曲应力一侧的高频淬火区发生氢脆开裂,裂纹形成后,活塞杆在外加应力作用下发生快速失稳断裂。在此基础上,提出了消除活塞杆氢脆隐患的改进措施。     

硫酸盐三价铬电镀中铵盐的作用及影响

研究了铵盐在硫酸盐体系三价铬电镀中的作用.通过赫尔槽试验、沉积速率、极化曲线、循环伏安法等方法研究了铵盐对三价铬镀液的电沉积特性的影响.并采用Tafel曲线、电化学阻抗谱EIS测试及铜盐加速醋酸盐雾试验(CASS),对在不同浓度铵盐的镀液中得到的镀层耐蚀性进行了测试.结果表明,铵盐在镀液中不仅起导电作用而且起配位作用....     

硫酸铈对三价铬钝化膜耐腐蚀性的影响研究

目的研究硫酸铈对三价铬钝化膜耐蚀性能的影响。方法通过在三价铬镀铬盐溶液中分别添加0.3、0.5、0.8、1.0、1.5 g/L的硫酸铈,然后通过极化曲线测试,对比不同硫酸铈添加量的钝化膜的腐蚀电流密度,确定硫酸铈在三价铬镀铬盐溶液中的最佳添加量,然后分别制备未添加硫酸铈和添加最佳添加量硫酸铈的三价铬钝化膜,通过电化学工作站CHI660E测量Tafel极化曲线和电化学阻抗谱。分析钝化膜的电化学性能,研究不同钝化膜的耐腐蚀性。观察试样表面的微观形貌,对比添加硫酸铈和未添加硫酸铈的钝化膜的微观形貌。结果通过极化曲线测试发现,当硫酸铈的添加量为1.0 g/L时,钝化膜的腐蚀电流密度小于其余添加量的钝化膜,添加硫酸铈和未添加硫酸铈的钝化膜的耐蚀性能不同,添加硫酸铈后的钝化膜性能得到改善,且钝化膜膜层的微观形貌发生改变。结论添加硫酸铈后,三价铬钝化膜的耐腐蚀性能增强。当硫酸铈的添加量为1.0 g/L时,腐蚀电流密度最小,为3.835×10~(-6) A/cm~2,耐腐蚀性能优于其余钝化膜。