Zn-Ni合金渗层的组织结构及腐蚀性能EI北大核心CSCD

为改善传统渗锌层组织结构及腐蚀性能,采用甲酸镍和锌粉作为渗剂金属,通过机械能助渗法在Q235钢表面制备Zn-Ni合金渗层。结合扫描电镜(SEM)、EDS能谱和X射线衍射仪(XRD),分析Zn-Ni合金渗层的表面、截面和断口形貌;利用极化曲线和电化学阻抗谱(EIS),表征Zn-Ni合金渗层在3.5%NaCl溶液中的电化学行为;通过中性盐雾试验测试Zn-Ni合金渗层的耐腐蚀性能。结果表明:制备得到Zn-Ni合金渗层的厚度为153μm;渗层主要由Γ(Fe_(11)Zn_(40))相、ζ(FeZn_(15))相和Ni_(2)Zn_(11)金属间化合物组成,渗层结合方式属于冶金结合;Zn-Ni渗层中性盐雾试验出现红锈的时间相比渗锌层延长240 h,自腐蚀电位从−1.222 V正移至−0.957 V,渗层电阻提高352Ω·cm^(2);Ni对改善渗层表面组织状态和提高渗层耐腐蚀性具有显著价值。通过添加甲酸镍制备的Zn-Ni合金渗层相比渗锌层组织结构和腐蚀性能得到明显改善。     

稀土元素La对金属表面粉末渗锌层组织结构和性能的影响

金属结构件表面经粉末渗锌后具有良好的耐腐蚀性能、渗锌层与基体的结合强度高等优点,但渗层结构及质量有待进一步提高。本文在金属结构件表面渗锌处理的渗锌剂中加入不同掺杂量的稀土元素La(质量分数分别为0 %,1.3 %,2.7 %,4.0 %,5.3 %),采用SEM观察表面形貌、XRD测定物相以及占比情况、激光共聚焦扫描显微镜(CLSM)生成超高分辨率的3D表面形貌图像以评估表面粗糙度特性、纳米压痕(Nano Indenter G200)研究渗层的硬度评估其机械性能。结果表明,渗锌剂中添加4.0 %稀土元素La可以更好地改善渗层的微观结构、增加渗层中柱状致密的δ相使渗层组织细化且致密、减少凹坑裂纹等缺陷的产生、提高渗层的均匀性,渗层在厚度方向上硬度有所提高,并且硬度分布更加均匀。通过测量材料开路电位(OCP)、极化曲线(Tafel)和电化学阻抗谱(EIS)表明添加4.0%的La元素形成的渗层耐腐蚀性能更好。     

氧化镧对TC4钛合金固体渗硼的影响

对固体渗硼剂(碳化硼+碳化硅)中添加氧化镧对钛合金渗硼层的表面形貌与相组成、渗层厚度、渗层硬度、渗层与基体的界面结合力以及渗层摩擦磨损性能的影响进行了研究。结果表明,固体渗硼剂中添加氧化镧(4.0%,质量分数)细化了渗层表面形貌组织;显著提高了渗层的厚度与表面硬度(增幅分别为50.7%和34.8%);提高了渗层与基体的界面结合力(增幅为37.25%);大幅提高了渗层在摩擦磨损过程中抗剥落性能以及渗层自身的抗裂性能。自身抗裂性能的提高与渗层中含有Ti金属物相从而提高渗层的韧性有关。添加氧化镧渗层与未添加氧化镧渗层相比,具有低的摩擦系数(0.12)且摩擦磨损表面无对摩件中Fe元素。     

TC4钛合金表面氧化镧催渗渗硼工艺优化

以渗层厚度和表面硬度为评定依据,采用正交试验对TC4钛合金表面氧化镧催渗渗硼工艺进行优化。结果表明,渗硼温度对渗硼层影响最大,其次为渗硼时间、B₄C含量和La₂O₃含量。最优的催渗渗硼工艺为：渗硼温度1050 ℃,渗硼时间20 h,渗硼剂配比20wt%B₄C+4wt%La₂O₃+76wt%SiC。渗层表面由TiB、Ti₂B₅、TiC和Ti组成;与未添加氧化镧渗硼层相比,添加氧化镧渗硼层厚度与表面硬度明显提高,耐磨性也得到显著改善。     

ZL303铝合金表面微弧氧化陶瓷膜的微结构和耐蚀性研究

为提高ZL303铝合金耐蚀性能,采用微弧氧化技术在ZL303铝合金表面制备陶瓷质氧化膜。通过扫描电镜观察了微弧氧化膜层表面及截面的微结构。利用X射线衍射仪分析了膜层的物相组成。采用腐蚀电化学和高温浸泡实验测试了微弧氧化膜层的耐蚀性。结果表明:所制备的膜层厚度约为13μm,主要由α-Al_2O_3和γ-Al_2O_3组成,外表面存在大量微米级等离子放电微孔。经微弧氧化处理后,试样的电化学阻抗半径增大,自腐蚀电位上升,腐蚀电流密度减小。在高温腐蚀环境中,微弧氧化膜层能有效阻挡腐蚀介质对铝合金基体的侵蚀破坏,耐蚀性能得到提高。     

42CrMo钢锌铝共渗层的组织及性能

研究了42Cr Mo钢在不同锌铝共渗温度、共渗时间条件下共渗层的组织及性能。用金相显微镜、扫描电镜观察了锌铝共渗层的形貌及厚度;用X射线衍射仪分析了共渗层的物相组成;对比了纯锌渗层与共渗层耐蚀性。结果表明:在400℃下保温不同时间,渗层的厚度随时间的增长而逐渐增加;在不同温度下保温3 h时,渗层的厚度随温度的升高而逐渐增大;锌铝共渗的试样比单纯渗锌试样的耐腐蚀性能好,渗锌件出红锈时间为50 h,渗锌铝件为127 h,有效延长了耐盐雾腐蚀时间。     

粉末渗锌钢渗层的形成机理及影响因素研究进展

粉末渗锌工艺是一种热扩散表面改性技术,将渗锌剂与钢构件在高温条件下接触,利用原子扩散作用,在构件表面形成一层合金保护层。作为一种工艺简单、环境友好的高效表面防腐处理工艺,粉末渗锌技术可有效改善金属材料的耐磨、耐蚀和耐氧化等性能,具有广泛的应用前景而备受研究者的关注。首先分析了粉末渗锌层的形成机理,并重点讨论了渗层的组织结构;然后,综述了保温温度、保温时间以及合金元素等因素对渗层形成的影响。研究者发现,升高温度和延长时间有益于渗层厚度的增加,但要合理控制,温度过高或时间过长不仅使渗层性能变差,还会增加能耗和降低生产率。此外,通过调整渗剂中合金元素的添加量以及种类,能够改善渗锌层的性能,但各类元素的最佳添加量以及其对渗层的改性机理还有待于进一步探究。目前,粉末渗锌生产中存在效率低的问题,在渗锌工艺中应用机械能助渗技术和纳米技术,可有效提高渗锌效率、改善渗层性能。最后,结合当前的研究现状,对粉末渗锌工艺的研究方向进行了探讨。     

氩离子轰击对中频-直流磁控溅射铝薄膜耐蚀性能的影响

目的研究氩离子轰击这种后处理工艺对TC4钛合金表面铝膜层结构和耐蚀性能的影响,为飞机钛合金紧固件的表面腐蚀防护工作提供理论依据。方法首先采用中频-直流相结合的磁控溅射离子镀方法在Ti-6Al-4V钛合金(TC4)基体表面制备铝膜,通过电化学方法研究膜层厚度和腐蚀时间对耐蚀性能的影响规律。其次,采用氩离子轰击工艺对膜层进行后处理,探讨氩离子轰击对膜层耐蚀性能的影响,同时利用SEM、EDS、AFM表征界面形貌,并分析耐蚀机理。最后,通过显微硬度仪和微纳米划痕仪测试膜层表面硬度和界面结合性能。结果随着膜层厚度从11.1μm增加至15.9μm,自腐蚀电流密度下降了76.6%,而当厚度由15.9μm增加至20.3μm时,自腐蚀电流密度又下降了24.3%。腐蚀浸泡时间达到24 h时,腐蚀产物在疏松氧化膜内的累积和覆盖阻碍了膜层的腐蚀;在48～72 h时,随着铝膜层相对疏松的腐蚀产物逐渐脱落,腐蚀逐渐加剧;浸泡至96h时,涂层表面出现宏观腐蚀坑。氩离子轰击后,膜层表面粗糙度增加,铝膜层自腐蚀电流密度由未轰击时的1.65×10~(-8)A/cm~2大幅度降低至7.29×10~(-10)A/cm~2。结论随着铝膜层厚度的增加,膜层耐蚀性逐渐增强。膜层在浸泡初期和中期,均具有较强的耐腐蚀性能;浸泡后期,膜层逐渐发生点蚀,耐蚀性能下降。表面氩离子轰击后,膜层的耐蚀性能、显微硬度和界面结合性能显著提高。     

稀土添加量对20CrMnTi钢表面碳铌复合渗层组织及性能的影响

目的提高20CrMnTi钢表面硬度及耐磨性能。方法采用粉末包埋法在20CrMnTi钢表面制备了碳铌复合渗层。粉末渗铌剂组成为铌粉、氧化镧、氧化铝及氯化铵,渗铌温度为950℃,保温时间为5 h。通过光学显微镜、扫描电子显微镜、显微硬度计、能谱仪、X射线衍射仪及微动摩擦磨损试验机,研究了不同La_2O_3添加量条件下,碳铌复合渗层的硬度、厚度、组织、物相组成及摩擦系数。结果不同La_2O_3添加量条件下,复合渗层主要由NbC相组成,厚度为23~28mm,硬度为2250~2950HV0.5。随着La_2O_3添加量的增加,复合渗层物相组成变化不明显,渗层晶粒尺寸先增大后减小,厚度逐渐下降,硬度先上升后逐渐下降,摩擦系数基本是先上升后下降。稀土添加量(质量分数)为0.5%时,其摩擦系数较低。结论粉末包埋复合渗铌渗剂中,La_2O_3的最佳添加量为0.5%,能细化渗层晶粒尺寸,有利于提高20CrMnTi表面碳铌复合渗层的致密性及硬度。     

镁合金微弧氧化膜耐蚀性表征方法的对比研究

制备结构、性能相近的AZ91D镁合金微弧氧化膜,通过浸泡、点滴及电化学实验表征膜层的耐蚀性,并结合SEM分析膜层腐蚀前后的表面形貌。本研究中6种耐蚀性检测方法的结果均表明：AZ91D镁合金经微弧氧化处理后耐蚀性显著提高; 失重与增重现象的共存使浸泡实验不能准确评定微弧氧化膜层耐蚀性的优劣; 点滴实验可以较快较准确地反映膜层的耐蚀性,但采纳点滴液开始变色的时间点为评价依据更合适,且测试耐蚀性较好的膜层时,点滴液中硝酸的含量提高到标准中的至少两倍时,才能达到快速检测的目的; 循环伏安、Tafel 极化、开路电位和电化学阻抗谱4种电化学实验能反映诸如腐蚀电位、腐蚀电流密度、阻抗值等更多的信息,可以进一步研究膜层的耐蚀原因。膜层的耐蚀性除了与膜厚、化学成分有关外,还与微观结构膜层内部和表面的密切相关。     

Study of Cerium and Lanthanum Conversion Coatings on AZ63 Magnesium Alloy Surface

采用扫描电子显微镜,X射线能谱,Tafel极化曲线和电化学阻抗谱法研究了铈镧转化膜对AZ63镁合金耐蚀性能的影响。结果表明,铈和镧的复合转化膜比单一稀土膜的表面更加均匀致密,对镁合金的耐蚀性有明显改善。双稀土转化膜的缓蚀效果随着浸泡成膜时间的增长而增加。延长时效时间有助于铈和镧的进一步氧化,耐蚀性能先增后减,时效48 h膜层的耐蚀效果最好。     

Corrosion resistance of cerium‐based chemical conversion coatings on AA5083 aluminium alloy

In this paper the effect of several parameters, such as temperature, time of immersion, cerium ions and hydrogen peroxide concentration, pH of the conversion solution, on the composition and morphology of the conversion layer are investigated as well as on its corrosion resistance in chloride environments. The cerium‐based chemical conversion coatings ennobles the corrosion potential and inhibits both the cathodic and anodic reactions rate. Using a cerium (III) chloride solution a not homogeneous coating is obtained and agglomerates with a “dry‐mud” morphology of mixed cerium‐aluminium oxide are deposited above the cathodic intermetallic particles, while using a cerium (III) nitrate solution the coating is more uniform but thinner than that obtained with cerium (III) chloride. Solution temperature below 50°C and time of immersion of 10 minutes produces a coating with better corrosion resistance.     

钝化处理对Al-B4C复合材料腐蚀行为的影响

采用三乙醇胺溶液对Al-B4C复合材料进行了表面钝化处理,通过电化学试验和浸泡腐蚀试验研究了钝化处理对Al-B4C复合材料腐蚀行为的影响。结果表明:钝化处理使Al-B4C复合材料表面生成双层结构的氧化膜,非晶内层氧化膜厚度约为2.5μm,外层氧化膜由三斜相和单斜相的Al(OH)3构成,厚度小于1μm;钝化处理后的AlB4C复合材料具有较大的极化电阻,表现出较好的耐腐蚀性能;经40℃硼酸溶液浸泡腐蚀1000h后,钝化Al-B4C复合材料的腐蚀质量增加和金属离子溶出显著低于未钝化Al-B4C复合材料的,说明钝化处理形成的氧化膜,能有效地提高Al-B4C复合材料的耐腐蚀性能。     

Corrosion and electrochemical behavior of aluminium treated with high-temperature pulsed plasma in CsCl–NaCl–NaNO3 melt

Dense protective layers of aluminium corrosion products, whose composition depends on the oxidation temperature, are formed on the surface of aluminium treated with high-temperature pulsed plasma (HTPP) without visible remelting and then held in a chloride–nitrate melt in conditions of anodic polarization. Modification of aluminium treated with HTPP changes the properties of 20 μm layer under its surface and the oxide layer formed by such treatment has different morphology: it consists of smaller crystals and so has the other protective properties as compared with aluminium untreated by plasma.     

Effects of rare earth metal addition on surface morphology and corrosion resistance of hot-dipped zinc coatings

Effects of rare earth metals (REM) addition on surface morphology and corrosion resistance of hot-dip galvanised steel were investigated. The corrosion resistance of steel samples galvanised with zinc and zinc alloys containing 0.05, 0.1, 0.2 and 0.5 wt.% REM were evaluated by various corrosion tests such as weight loss in salt spray chamber and natural sea water, sacrificial protection ability in contact with fog in salt spray chamber and after immersion in sea water, potential-time in sea water and linear polarisation in sodium chloride solution. Surface morphology and nature of the corrosion products were also investigated. The results indicated that the addition of small amounts of REM to the molten zinc galvanising bath can improve the corrosion resistance of hot-dip galvanised steel. Mechanisms by which the corrosion resistance of hot-dip galvanised steel are improved in presence of REM have been discussed.     

The relationship between the corrosion resistance and impurity content of aluminium oxide layers

In the last few years there has been an increased production and application of aluminium foil of under 20 μm thickness all over the world. Household foil is often stored in a wet environment, where the surface is only protected against corrosion by an aluminium oxide layer produced during manufacturing. In this study it has been shown that the aluminium-water vapour reaction is greatly affected by the composition and structure of the amorphous oxide layer on the surface and this depends on the composition of base metal and on the annealing of the foil. The incubation period of aluminium hydroxide nucleation is shortened and its growth rate accelerated by alkali and alkaline earth metal cations incorporated in the oxide layer. In particular the corrosion resistance is decreased by the presence of alkali (Li) and alkaline earth metal (Mg) cations in the oxide layers.     

含稀土HAl77-2铝黄铜的腐蚀行为

通过测定3种不同成分的铝黄铜在NaCl（3.5%）溶液和NaCl（3.5%）＋NH4Cl（0.5 mol/L）溶液中的腐蚀速率、电化学行为分析,以及对腐蚀产物层进行SEM观察和XRD分析,研究了铝黄铜的腐蚀行为。结果表明：添加Ce可以降低铝黄铜在NaCl（3.5%）溶液中极化时的自腐蚀电流密度;含Ce的Cu-Zn-Al-Ni-B-Ce在NaCl（3.5%）溶液中腐蚀后腐蚀产物层表现出最佳的腐蚀形貌和耐腐蚀性能,而添加稀土并不能改善铝黄铜在NaCl（3.5%）＋NH4Cl（0.5 mol/L）溶液中的耐腐蚀性能;联合添加As和Ce的Cu-Zn-Al-Ni-As-B-Ce在这2种介质中的耐腐蚀性能反而下降。     

煤气管道用耐酸钢硫酸腐蚀行为研究

高炉煤气输送管道通常采用普碳钢,而煤气管道中含有硫酸、硝酸和氯离子等多种腐蚀性介质,对管道造成腐蚀,管道使用寿命低。针对研发的煤气管道用耐酸钢,采用均匀腐蚀全浸试验对其硫酸腐蚀行为进行了研究,利用扫描电镜(SEM)、电子探针(EPMA)、激光共焦扫描显微镜(LSCM)等手段揭示其腐蚀行为。结果表明,煤气管道用耐酸钢有优异的耐硫酸腐蚀性能;Cu、Sb、Cr等耐腐蚀元素的加入有利于改善点蚀现象,并在耐酸钢表面形成一层致密的不溶于硫酸的富含Cu、Sb、Cr等元素的钝化膜,从而增强耐酸钢的耐硫酸腐蚀性能;适量的S元素含量有利于提高钢的耐硫酸腐蚀性能。     

Formation and characterization of anodized layers on CP Ti and Ti-6Al-4V biomaterials

The biocompatibility of titanium and Ti-6Al-4V alloy materials has been attributed to the presence of a passive surface oxide layer. In this investigation, the feasibility of creating a thick, porous oxide layer by anodizing commercially pure Ti and the titanium alloy in sulfuric acid under potentiostatic conditions was examined. Characterization of the anodic oxide layers was carried out to determine their thickness, morphology and composition. The thickness of the oxide layers, as determined by Rutherford backscattering spectrometry, was found to be a function of applied potential, anodizing time and electrolyte temperature. Scanning electron microscopy investigations revealed that under suitably controlled experimental conditions, a very porous (10 μm diameter pores) surface layer could be formed. Incorporation of sulfate ions into the oxide layer was evident from depth profile analysis by Auger electron spectroscopy. The isoelectric point of the oxide layer formed on the alloy surface was measured to be 5.8.     

Electrochemical impedance spectroscopy study of surface films formed on copper in aqueous environments

The electrochemical behavior of pure copper has been studied in aqueous environments using linear polarization and electrochemical impedance spectroscopy (EIS) techniques as a function of immersion time. The effect of pollutants (like chloride, sulfide and ammonium ions) on the nature of films formed on the copper surface has been studied. All the surfaces revealed the presence of a porous oxide layer. The corrosion resistance decreased with increasing amount of chloride ions. The addition of Na₂S in the environments in the absence of any chloride species was beneficial for corrosion resistance. EIS data suggested that the capacitance of the films formed in chloride environments was higher. The surfaces obtained in presence of chloride ions were relatively rough and deeply attacked. The total impedance decreased after 432 h of immersion in solutions possessing chloride ions. The damaging role of chloride ions and the relatively less severe effect of sulfide ions were noted.