Corrosion resistance of multilayer coatings of nanolayered Cr/Ni electrodeposited from Cr(III)-Ni(II) bath

In this study the corrosion resistance of chromium and nickel single layers and multilayer coatings of nanolayered Cr/Ni, electrodeposited from Cr(III)-Ni(II) baths on low carbon steel substrates, has been studied. The coatings were electrodeposited from a bath using pulse current and modulated agitation. The total thickness of single layer and multilayer coatings was fixed at 5 μm and multilayer coatings with different modulation wavelengths and Cr to Ni thickness ratio were electrodeposited. Corrosion behavior of coatings was then studied by using potentiodynamic polarization test and electrochemical impedance spectroscopy in 0.1 M H₂SO₄. The results showed that Cr and Ni single layers had low corrosion resistance due to the presence of surface cracks and pores, respectively. On the other hand, optimized 20 nm Cr/50 nm Ni multilayer deposition significantly improved corrosion resistance.     

Corrosion behaviour of CrN/Cr multilayers on stainless steel deposited by unbalanced magnetron sputtering

This paper reports the results of the influence of bilayer period (Λ) and total thickness (f) on the corrosion resistance of magnetron-sputtered CrN/Cr multilayers. Corrosion tests were carried out by potentiodynamic polarization with 0.5 M H₂SO₄ + 0.05 M KSCN solution and electrochemical impedance spectroscopy (EIS) with 3% NaCl solution. Measurements were also taken on the uncoated substrate and hard chromium coatings for comparison. Multilayer microstructure and morphology were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) and chemical composition was studied by energy dispersive X-ray analysis (EDX).The experiments showed that CrN/Cr coatings having lower bilayer period and lower thickness increased their efficiency as a barrier and improved the corrosion resistance of all coatings evaluated.     

汽车用镁合金铈盐改性硅烷复合膜的耐蚀性

目前镁合金表面稀土-硅烷化改性多采用复合工艺,简单硅烷化处理研究较为少见。将不同含量的硝酸铈直接添加到KH-550硅烷溶液中,应用简单化学浸渍法在AZ91D压铸镁合金表面制备了铈盐改性硅烷复合膜;通过点滴腐蚀试验、全浸腐蚀试验和电化学交流阻抗谱评价了铈盐改性复合膜的耐蚀性能,利用扫描电子显微镜和椭偏仪分析了铈盐改性复合膜的表面微观形貌和厚度。结果表明:与硅烷膜相比,铈盐改性硅烷复合膜较均匀、致密、平整,厚度明显增加;随着硝酸铈含量的增加,铈盐改性硅烷复合膜的耐蚀性能先上升后下降,当硝酸铈掺杂量达到0.50 g/L时,复合膜的耐蚀性能最佳;随盐水浸泡时间的延长,复合膜的低频阻抗值先增大后减小,表明其具有一定的"自修复"能力。     

Nafion/polypyrrole and Nafion/DMSO Organic Coatings for Magnesium Protection

Nafion/polypyrrole and Nafion/Dimethysulfoxid （DMSO） organic coatings were prepared on the surface of pure magnesium by simple immersion and heat treatment. The morphologies and corrosion resistance of the organic coatings were investigated by using optical microscopy and electrochemical corrosion testing, respectively. It is shown that Nafion/polypyrrole organic coatings resulted in the corrosion resistance of magnesium decreasing; while Nafion/DMSO organic coatings can effectively improve the corrosion resistance of magnesium. Also, the corrosion resistance increased with the thickness of the Nafion/DMSO organic coating increased.     

铝合金表面等离子体电解氧化陶瓷涂层在NaCl溶液中的电化学阻抗谱研究

通过调整电解液中硅酸钠的浓度, 利用等离子体电解氧化(PEO)技术在铝合金LY12表面制备了各种陶瓷涂层, 利用光学显微镜、XRD、电化学阻抗谱(EIS)对涂层的形貌、成分和涂层在NaCl溶液中耐腐蚀性能进行了研究. 结果表明: 提高电解液中硅酸钠的浓度可以使得涂层的总厚度增加, 但过高或过低的浓度都会导致致密层厚度的减薄. 当浓度为20g/L时, 所制备的涂层的成分以氧化铝为主; 当浓度为40g/L时, 涂层的成分主要是莫来石和氧化铝; 当浓度超过60g/L 时, 涂层的成分主要为非晶相. EIS的研究表明, 涂层耐腐蚀性取决于涂层中的致密层, 增加致密层的厚度可以提高PEO涂层的耐腐蚀性, 在中性、酸性、碱性腐蚀介质中, PEO涂层都显示出对基体良好的保护作用.     

吸波剂含量和涂层厚度对微波吸收性能的影响

以具有强磁损耗特性的磁粉、电阻型和电介质型物质作为吸波剂,制备出了具有阻抗渐变结构的3层复合雷达吸波涂层,研究了吸波剂用量和涂层厚度对吸波性能的影响.结果表明,增加表层、中层或底层吸波剂含量及涂层厚度,均能使吸波性能曲线向低频端方向移动,反之,吸波性能曲线向高频端方向移动;选择适当的吸波剂含量或者一定厚度的涂层才能拓宽、加深吸波性能.制得的试样中反射损耗可达-35.74和-39.25dB,其频宽(＜-10dB)分别为3.52和2.84GHz.     

Integrated indentation tests of metal-ceramic nanocomposite coatings

The results of a study of the strength and erosive properties of ion plasma layered coatings of various metal and ceramic (nitride) systems are described. The total thickness of the coating is a few microns, while the thickness of each of the layers does not exceed two or three tens of nanometers. The use of different indentation schemes provides a set of physicomechanical properties responsible for the coating strength. The properties are subjected to multiparametric optimization to obtain a satisfactory correlation with the data of bench erosion tests of the coatings. It is found that the erosion resistance of nanocomposite coatings, which is commonly determined in complex bench or full-scale tests, can be reliably diagnosed from the set of the physicomechanical properties of the coatings measured in the laboratory.     

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.     

碳弧熔覆工艺对熔覆层组织及性能的影响

为获得高硬度、高耐磨性的表面合金层,将镍基自熔合金粉末预先涂覆在Q235钢表面,利用碳弧热源进行熔覆制备熔覆层。通过金相显微镜、硬度计及磨粒磨损试验机对熔覆层表面的组织及性能进行测试,研究焊接电流和涂覆层厚度对熔覆层组织和性能的影响。结果表明:焊接电流相同,增加涂覆层厚度,熔覆层的表面硬度和耐磨性呈现先增加后降低的趋势;涂覆层较薄时,熔覆层硬度、耐磨性随电流增大而下降,涂覆层较厚时,熔覆层硬度、耐磨性随电流增大而呈上升趋势;当涂覆层厚为4 mm,焊接电流为200 A时,组织为镍基固溶体加共晶物,共晶组织为镍基固溶体与多种碳化物、硼化物共晶,硬度最高,为54.3 HRC,耐磨性最好。     

Optimising deposition parameters of W-DLC coatings for tool materials of high speed steel and cemented carbide

The paper presents the results of investigations on the selection of optimal deposition parameters for W-DLC coatings produced by pulsed reactive magnetron sputtering in order to obtain the coatings with high adhesion to the high speed steel (HSS) and cemented carbide (HM) substrates. To optimise the deposition parameters for W-DLC coatings Taguchi's method was used. An acetylene flow rate, the substrate bias voltage, the thickness of W-DLC coatings and the thickness of chromium sublayer were selected as deposition parameters and for each of them three levels of values were determined. Adhesion, wear resistance and hardness of coatings were chosen as the criteria for selecting the optimum deposition parameters. The test results showed that all the selected parameters have a significant effect on the adhesion of coatings. The thickness of W-DLC coatings has a very significant effect on the adhesion to HSS substrates and in a case of HM substrates the same effect has the thickness of a chromium sublayer. The wear resistance of coatings increases with an increasing acetylene flow rate and decreases with the increasing substrate bias voltage. High correlation was found between the H/E ratio of coatings and their wear resistance as well as toughness. The W-DLC coating showing the best properties (L_C3 ≈ 90 N, k_V = 3.8 × 10⁻⁷ mm³/Nm) was marked by the nanocomposite structure containing about 40% of nanocrystalline tungsten carbide phase and 60% of amorphous carbon matrix.     

镁表面Nafion/聚吡咯与Nafion/二甲基亚砜有机涂层耐蚀性能的研究

采用浸镀法在镁基体表面制备了Nafion/聚吡咯和Nafion/二甲基亚砜(DMSO)有机涂层,利用光学显微镜和电化学测量系统研究了有机涂层的形貌及其耐蚀性能.结果表明,Nafion/聚吡咯有机涂层的厚度随着浸镀次数的增加几乎不变,且Nafion/聚吡咯有机涂层降低了镁的耐蚀性能;而Nafion/DMSO有机涂层的厚度则随着浸镀次数的增加而线性增加,并且Nafion/DMSO有机涂层能有效地改善镁的耐蚀性能,耐蚀性能随着涂层厚度的增加而提高.与无涂层的试样相比,耐蚀性能最高提高18倍.     

Influence of the Porosity of a Plasma-Electrolytic Coating on the Corrosion Resistance of D16 Alloy

Materials Science - We study the effect of the coating thickness on the corrosion resistance and porosity of oxide-ceramic coatings on D16 alloy. The coatings were synthesized in an alkaline...     

Designing multilayer diamond like carbon coatings for improved mechanical properties

New multilayer coatings were produced by incorporating alternating soft and hard DLC layers enabled by varying the bias voltage during deposition process while maintaining a constant hard-to-soft layer thickness ratio.These coatings were deposited onto a Cr/Cr Cxgraded layer by closed field unbalanced magnetron sputtering(CFUBMS).The cross-sectional analysis of the coatings showed that the multilayer coatings possess sharp interfaces between the soft and hard layers with the hard to soft layer thickness ratio(1:1.33)constant in all the coatings.Raman analysis uncovered the increasing sp³character of the DLC coatings as a result of decreasing ID/IGratio and increasing full width at half maximum(FWHM)values of the G band peak induced supposedly by an increase in bias voltage during hard layer deposition.Nanoindentation tests showed an increase in hardness of the DLC coatings which can be correlated with the increase in the sp³content of the coatings as well as decreasing sp²-C cluster size,as calculated from the ID/IGratio.Furthermore,the coatings exhibited excellent plastic deformation resistance and adhesion strength upon microindentation and scratch testing,respectively.Although further investigations are required to assess coating durability,the multilayer design could offer the DLC coatings with a rare opportunity to combine the high hardness with damage resistance with a constant bilayer thickness and without the need to introduce complex multilayer system.     

Effects of aluminum content and mechanical nano-alloying time on the preparation of titanium-aluminum composite coatings on magnesium-lithium alloy

A titanium-aluminum composite coating was successfully fabricated on magnesium-lithium alloy substrate by mechanical nano-alloying treatment (SMNAT). The effects of aluminum content and mechanical nano-alloying time on the microstructure and properties of titanium-aluminum composite coatings were investigated. The experimental results showed that the ratio of titanium-aluminum powder has a significant effect on the preparation of the coating. Low aluminum content and high aluminum content in the mixture powder resulted in the formation of the coatings with inhomogeneous thickness. The titanium-aluminum ratio of 3 : 1 was considered to be optimal for fabricating the coating with homogeneous thickness under the selected milling parameters. The hardness of top surface layer on titanium- aluminum coatings decreased from 292.0 HV 0.01 to 121.4 HV 0.01 with the increase of aluminum content. Additionally, the prolongation of treatment time facilitated to increase the thickness and density of the coatings, resulting to enhance their hardness and corrosion resistance.     

新型Mg-Zn-Y-Nd-Zr镁合金表面复合涂层的耐腐蚀性能

为了控制镁材及镁合金在人体中的生物降解速率,采用微弧氧化法、电化学沉积法及微弧氧化+电化学沉积法在新型Mg-Zn-Y-Nd-Zr镁合金表面制备了3种涂层。利用JSM-5610V扫描电子显微镜、TESCANTS5130 SB能谱分析仪、Bruker D8 ADVANCE X射线衍射仪、VS-2005涂层附着力自动划痕仪、RST200F电化学工作站对3种涂层的形貌、成分、结构、厚度、结合力以及电化学性能进行了检测。结果表明:3种涂层均能提高新型Mg-Zn-Y-Nd-Zr镁合金的电化学性能,改善其耐蚀性;微弧氧化+电化学沉积层较单一微弧氧化层及电化学沉积层在致密性、结晶度、厚度、结合力、耐腐蚀性能方面都具有更强的指标。     

SiO2或TiO2纳米粒子/含氟聚丙烯酸酯复合涂层的制备及其防腐蚀性能

通过在含氟聚丙烯酸酯(PFHI)溶液中添加固体纳米粒子,经涂覆热固化后得到了厚度约为1 μm的SiO₂或TiO₂纳米粒子/PFHI复合涂层,考察了SiO₂或TiO₂两种纳米粒子质量分数对复合涂层表面性质和防腐蚀性能的影响。利用Tafel极化曲线和电化学交流阻抗(EIS)测试研究了复合涂层在3.5wt% NaCl溶液中的电化学防腐蚀性能,并运用XPS、衰减全反射傅里叶变换红外光谱(ATR-FTIR)、TG-DTA、SEM、光学接触角(OCA)手段对复合涂层进行表征。结果表明,添加SiO₂或TiO₂纳米粒子均可大幅提高PFHI涂层的电化学防腐蚀性能,SiO₂与PFHI质量比为0.3的SiO₂/PFHI复合涂层电荷转移阻抗值R_ct与PFHI涂层相比上升了2个数量级。SiO₂或TiO₂纳米粒子增大了涂层表面粗糙度,与PFHI紧密结合形成致密的复合涂层,提高了涂层的疏水性和致密性,从而改善了涂层的抗腐蚀性能。      

Preparation and Properties of Plasma Spraying Cu-Al2O3 Gradient Coatings

In order to overcome the limitations of low adhesion strength and poor thermal-shock resistance of pure ceramic coatings, Cu-Al2O3 gradient coatings were fabricated by plasma spraying. The microstructure and distribution of Cu-Al2O3 gradient coatings were analyzed. The adhesion strength, thermal-shock resistance and porosity of the coatings were tested. The results show that the composition of the gradient coatings has a gradient distribution along the thickness of coatings. As copper has a relatively low melting point and the molten copper has good wettability on the surface of Al2O3, it can be melted sufficiently and could fill the interstices and pores among the spraying particles effectively, thus improves the adhesion strength, thermal shock resistance and reduces the porosity. The adhesion strength of the gradient coating is 15.2 MPa which is two times of that of the double-layer structure coating.     

7075铝合金微弧氧化电源波形对膜组织和性能的影响

为探讨不同电源波形对7075铝合金微弧氧化膜的影响,在Na2SiO3电解液体系中,分别采用恒直流、直流脉冲及交流不对称波形对7075铝合金进行微弧氧化,通过扫描电镜和X射线衍射仪分析了3种膜层的微观形貌和组成,考察了膜层的厚度、硬度、致密层比例及耐蚀性。结果表明:交流不对称氧化法获得的氧化膜性能最佳,膜层厚度达到100μm,硬度达到1 500 HV,致密层比例高达70%以上,耐蚀性最优。     

Korrosionsuntersuchungen an mittels PVD mit Zn und Zn/Mn beschichteten Stählen

Corrosion Studies of Steels Coated by means of PVD with Zn and Zn/Mn Alternative methods for hot dip‐ or electrogalvanic deposition of zinc coatings on steel are gas phase depositions (PVD). They posess high flexibility with respect to alloy composition, and are environmentally harmless. However, a PVD‐coated steel must have at least the same corrosion resistance than steels with “classical” surface finishing. Therefore, the corrosion behaviour of Zn‐coatings and Zn/Mn/system‐coatings deposited by electron beam evaporation without and with ion beam assistance (IBAD) on low alloy steel, was determined by means of salt spray test and electrochemical potential/time measurements. At first the influence of chemical and irradiation pre‐treatment and ion bombardment during deposition on the corrosion resistance of the coatings was investigated. Than the effect of the Zn‐layer thickness was determined in comparison with an 8μm thick electrogalvanized reference coating. Finally Zn/Mn‐alloys, Zn/Mn‐multilayers and Zn‐coatings with Mn‐ or Zn/Mn‐surface layers (top layers) were investigated. By means of optimised pre‐treatment and ion bombardment conditions one obtains, considering the layer thickness, PVD‐Zn coatings with corrosion resistance comparable with the reference layer. The best Mn‐containing coatings are Zn‐coatings with Mn‐toplayer. They surpass the corrosion resistance of the reference layer considerably. Additionally it could be shown that in tendency the potential/time measurements agree very well with the results of the salt spray test.     

工艺方法对热浸镀铝层质量的影响

通过目视检查、硝酸腐蚀失重法、中性盐雾腐蚀试验和镀层显微分析等手段,研究了一浴法、二浴法及钝化法工艺对钢材热浸镀铝镀层质量的影响,从镀层厚度、连续性、耐蚀性和显微组织形貌几个方面进行了分析比较.结果表明:二浴法的镀层质量最好,耐腐蚀性最佳.钝化法的镀层耐腐蚀性最差.