电解剥离过程中热镀锌合金化镀层的阳极溶解机制

分析了电解剥离过程中热镀锌合金化镀层的阳极溶解机制。结果表明,在GA镀层电解剥离的初始阶段,主要发生Zn的氧化,电解剥离过程中存在Zn和Fe之间的电耦合反应。由于镀层中微裂纹的存在,阴极反应区和镀层裂纹缝隙中会同时发生析氢反应,从而导致电偶腐蚀发生并形成诱导电流。当电解质溶液中存在氯离子时,Zn和Fe之间也会发生电耦合反应,该反应可以在一个非常小的局部区域内进行,反应过程中,氢的形核析出既可以是氢离子的重组,也可以是少量Zn和Fe的溶解反应。GA镀层中Fe-Zn金属间化合物同时发生电化学反应而溶解的现象只能在缝隙中发生,由于细小缝隙表面形成的活化区非常小,因此,GA镀层中的Fe-Zn相将分别发生溶解,从而保证了GA镀层中不同相之间的电压跃迁。     

合金化热镀锌镀层结构的电化学研究

用恒电位法，采取足够低的电位扫描速度，测定镀层的极化曲线，结合X射线衍射分析和扫描电镜研究了合金化热镀锌镀层组织。     

热镀锌钢板镀层合金化过程铁-锌相变的原位观察

用ESEM原位观察了铝含量不同的两种热镀锌钢板合金化过程中镀层表面和断面铁-锌合金相的生长,并用GDOES分析了镀层中元素分布和相结构的变化。实验结果表明：铝含量对热镀锌钢板合金化过程中镀层结构的变化具有重要的影响。铝含量为0.13%时,镀层从ζ相的形成到转变为δ相的过程是均匀进行的,铁-锌合金相均匀地生长,镀层的相结构以δ相为主;铝含量为0.22%时,界面处的铁-锌反应不能同时进行,合金化过程局部被延迟,镀层中形成了大量的暴发组织,ζ相及δ相的形成时间不同且不能均匀有序地形成,镀层的相结构是δ和ζ相的混合物。     

热镀锌镀层铝含量分析

铝是热浸镀锌中非常关键的金属元素,锌锅中铝含量决定了镀层的结构以及锌锅锌浴行为。本文分析了大生产下的GI和GA板镀层中的铝含量,结果表明,不管是GI或GA,带钢的运行速度即热浸镀时间将影响Fe2Al5抑制层的厚度,影响带钢从锌液中带走的铝含量。纯锌GI板,在有效铝含量为0.18%~0.20%的情况下,或者合金化GA板,在有效铝含量为0.125%~0.135%的情况下,镀锌时间越长或速度越慢,抑制层越厚,镀层中铝含量越高。在实际工业生产中锌锭的添加要考虑速度因素。本文目的是寻找镀层消耗铝的规律,为优化锌锭添加制度、稳定控制锌液成分做准备。     

连续热镀锌镀液铝含量的控制

要： 分析了热镀锌镀液铝含量对镀层质量的影响,并结合攀钢热镀锌生产实践,探讨了镀液铝含量稳定性的控制措施。结果表明,将热镀锌镀液铝含量控制在016%～020%,可获得较佳的产品质量;通过控制锌锭及调铝用合金锭的成分及添加方式,并采用前馈法调铝,可以确保镀液铝含量控制的稳定性。     

锌液中Al含量对合金化镀锌板镀层抗粉化性能的影响

用扫描电镜(SEM)、电子能谱(EDS)、X射线衍射(XRD)等方法研究了锌液中Al含量对镀层抑制层、镀层结构以及镀层抗粉化性能的影响。结果表明,随着锌液中Al含量的减少,抑制层晶粒增大;在相同的合金化工艺下,镀层合金化程度加大,抗粉化性能恶化。     

热镀锌合金化产品镀层铁含量工艺控制研究

连续热镀锌线合金化生产的工艺控制难度较大,合金化产品镀层铁含量偏低,会造成表面欠合金缺陷;铁含量偏高,会造成粉化缺陷,影响用户冲压使用。本文通过对连续热镀锌线合金化生产工艺参数控制的研究,提出了相应控制措施,将合金化产品镀层[w(Fe)]控制在8%～10%范围内。     

合金化热镀锌钢板抗粉化性能的研究进展

综述了合金化热镀锌钢板抗粉化性能的研究进展,重点论述了镀层相结构的形成机理和镀层相结构对镀层抗粉化性能的影响,同时介绍了镀层抗粉化性能的其它影响因素。     

合金化热镀锌钢板的性能影响因素及研究进展

叙述了影响合金化热镀锌板性能的各种因素,包括镀锌原板(钢板品种、表面质量、微合金化元素)、热浸镀及合金化过程工艺参数、锌锅内化学元素、镀层相组成等对合金化热镀锌板最终质量的影响。分析了DP、TRIP钢等先进高强钢热镀锌及合金化过程中出现的问题,针对这些问题,给出了各钢种的最佳合金化工艺及适用冲压等使用条件要求的镀层相组成。     

热镀锌钢板镀层相结构研究

应用制备透射电子显微镜截面(Cross-sentional)样品的聚焦离子束技术(Focus ion beam, FIB)将热镀锌用钢板制备成透射电子显微镜截面样品,透射电子显微镜(Transmission Electron Microscope, TEM)观察截面样品中镀层中存在的各种金属间化合物(相).通过电子衍射证明在热镀锌钢板镀层中存在有Γ相和δ相.     

热镀锌合金化工艺对镀层表面摩擦特性的影响

采用SEM和AFM对不同合金化工艺的热镀锌合金化镀层断面结构和表面形貌进行观察和表征,并用摩擦系数仪测定了压力对不同工艺的镀层表面摩擦系数的影响,分析了合金化工艺和载荷对热镀锌合金化钢板(简称GA钢板)镀层表面摩擦特性的影响。结果表明,合金化时间为50 s时镀层表面的摩擦系数最大,此后随着合金化时间的延长镀层表面的摩擦系数基本保持不变;不同工艺的合金化镀层表面的相结构不同,当镀层表面以ζ相为主并伴有少量η相或以块状ζ相及致密的栅柱状δ相晶体为主时,镀层表面较平滑,表面没有出现明显的火山口状形貌时镀层表面的摩擦系数最小;随压应力的增加,镀层表面摩擦系数逐步增大,但是在较大压应力作用下,镀层表面摩擦系数的增幅明显降低。     

Study on wear behavior of plasma electrolytic oxidation coatings on aluminum alloy

Thick and hard ceramic coatings were fabricated on A356 aluminum alloy by using plasma electrolytic oxidation(PEO) technique.The microstructure and phase composition of the PEO coatings were examined by using SEM and XRD method.It is found that the PEO coatings are mainly composed of crystalline α-Al2O3 and mullite.The dry sliding wear test of PEO coatings were carried out on a ring-on-ring wear machine.Results shows that there is hardly no wear loss of polished PEO coatings while the wear rate of uncoated aluminum alloy is 4.3×10-5 mm3·(N·m)-1 at a speed of 0.52 m·s-1 and a load of 40 N.     

热镀锌合金化镀层相结构对摩擦特性与粉化量的影响

利用XRD、SEM、摩擦因数测量仪及双杯突试验机,研究了热镀锌合金化钢板(GA)镀层的相结构对摩擦特性与粉化量的影响。结果表明,随着GA镀层表面ζ相含量的增加,表面铁含量的降低,镀层表面的摩擦因数逐渐增加。相反,随着镀层中铁含量的增加,合金化镀层的粉化量逐渐增加。     

Soft chemical stripping of aluminide coatings and oxide products on Ni superalloys

Turbine components are submitted to very aggressive environments and particularly to high temperature corrosion and/or oxidation. Because of their high cost, they have to be repaired instead of being replaced. Prior to refurbishment and recoating, the components have to be fully stripped to remove the oxide products and defective coatings.In this work, various soft chemical stripping methods are studied based on pitting acids and agents as well as oxidising acids in organic and aqueous media. The effect of the immersion time is also investigated. The feasibility of the dissolution reactions has been evaluated through thermodynamic calculations. It will be shown that the most effective baths are those containing relatively high concentrations of pitting reagents in organic media. Aqueous solutions lead to pitting of the superalloy. The stripping mechanisms have been discussed in terms of the dissolution of coating grain boundaries once the solution has passed through the oxide scales.     

Plasma Electrolytic Oxidation of Arc-Sprayed Aluminum Coatings

Different posttreatment methods, such as heat treatment, mechanical processing, sealing, etc., are known to be capable to improve microstructure and exploitation properties of thermal spray coatings. In this work, a plasma electrolytic oxidation of aluminum coatings obtained by arc spraying on aluminum and carbon steel substrates is carried out. Microstructure and properties of oxidized layers formed on sprayed coating as well as on bulk material are investigated. Oxidation is performed in electrolyte containing KOH and liquid glass under different process parameters. It is shown that thick uniform oxidized layers can be formed on arc-sprayed aluminum coatings as well as on solid material. Distribution of alloying elements and phase composition of obtained layers are investigated. A significant improvement of wear resistance of treated layers in two types of abrasive wear conditions is observed. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007.     

Ti基板上磷酸钙薄膜的电沉积

主要研究电沉积条件如何影响沉积产物磷酸钙涂层的晶相。实验采用金属Ti作为基板,电解液为Ca(NO3)2(45mmol/L)与NH4H2PO4(25mmol/L)的稀混合液,通过改变沉积温度、沉积时间、电解液的pH值等参数,利用XRD、SEM表征沉积产物。结果显示:温度对晶相转变的影响最大,37℃时获得的晶相只有DCPD(CaHPO4·2H2O),当沉积温度升高到60℃时,HAP(Ca10(PO4)(OH)2)相含量增加。沉积时间对沉积产物的晶相类型没有影响。随着pH值的升高,DCPD和OCP(Ca8(HPO4)2(PO4)4·5H2O)相含量均在增加,证明高pH值不仅能影响晶相生长,而且能诱导晶相转变。SEM结果表明,在3V的沉积电压下,都能够得到厚度均匀的沉积涂层,但是以45℃为沉积温度并沉积15min时,Ti基板上得到的磷酸钙盐涂层最均匀,并且得到的HA前躯体比较有利于实验后处理,以得到质量较好的HA涂层。     

Ion implantation and diamond-like coatings of aluminum alloys

In an attempt to increase the wear resistance of some key automotive components, General Motors Research and Development Center initiated a study to determine the potential of surface modification as a means of improving the tribological properties of automotive parts, and to investigate the feasibility of mass producing such parts. This paper describes the plasma immersion ion implantation system that was designed for the study of various options for surface treatment, and it discusses bench testing procedures used for evaluating the surface-treated samples. In particular, both tribological and microstructural analyses are discussed for nitrogen implants and diamond-like hydrocarbon coatings of some aluminum alloys.     

高强度铝合金微等离子体电解氧化陶瓷质膜层影响因素

微等离子体电解氧化是在阳极氧化基础上发展起来的直接在轻合金表面原位生成γ-Al2 O3和α-Al2 O3陶瓷质膜的一项表面工程新技术.α-Al2 O3对陶瓷质膜层的性能起决定性作用,最大限度地促进α-Al2 O3的形成,是改善铝合金表面综合性能的关键.经过对国内近20个单位的调研,发现该技术在军工、航空、航天、机械等领域有着迫切的需求和广泛的应用前景,有望部分替代硬质氧化膜实现大规模生产.本文从基体材料、溶液特性及电参数三方面分析铝合金微等离子体氧化膜层的影响因素,重点分析基体合金元素对陶瓷质膜层的影响.指出该技术在高强度铝合金应用领域的发展方向并对其前景进行了展望.     

电解低钛铝制备Al-9%Si合金的晶粒细化

分别以纯铝和电解低钛铝为母材制备Al-9%Si合金,对Al-5%Ti、Al-5%Ti-1%B和Al-4%B中间合金对纯铝制备合金的晶粒细化效果与Al-4%B对电解低钛铝制备合金的晶粒细化效果进行了对比试验研究。结果表明:Al-5%Ti-1%B中间合金的细化效果明显优于Al-5%Ti中间合金,向电解低钛铝制备的Al-9%Si合金中按51∶钛硼质量比添加Al-4%B中间合金,可获得比Al-5%Ti-1%B中间合金更好的细化效果;在硼添加量较低时,细化效果也优于Al-4%B细化纯铝制备合金。对试验结果进行了讨论,对铝硅合金的细化机理进行了分析。