Comparison of microstructure and mechanical properties of chromium nitride-based coatings deposited by high power impulse magnetron sputtering and by the combined steered cathodic arc/unbalanced magnetron technique

Sliding, abrasive, and impact wear tests were performed on chromium nitride (CrN)-based coatings deposited on mirror-polished M2 high speed steel substrates by the novel high power impulse magnetron sputtering (HIPIMS) utilising high peak cathode powers densities of 3000 W cm⁻². The coatings were compared to single layer CrN and multilayer superlattice CrN/NbN coatings deposited by the arc bond sputtering (ABS) technique designed to improve the coating substrate adhesion by a combined steered cathodic arc/unbalanced magnetron (UBM) sputtering process. The substrates were metal ion etched using non-reactive HIPIMS or steered cathodic arc at a substrate bias voltage of −1200 V. Subsequently a 2- to 3-μm thick CrN or CrN/NbN coating was deposited by reactive HIPIMS or UBM. No bias was used during the HIPIMS deposition, while the bias during UBM growth was in the range 75-100 V. The ion saturation current measured by a flat electrostatic probe reached values of 50 mA cm⁻² peak for HIPIMS and 1 mA cm⁻² continuous during UBM deposition. The microstructure of the HIPIMS coatings observed by transmission electron microscopy was fully dense in contrast to the voided columnar structure observed in conventional UBM sputtered CrN and CrN/NbN. The sliding wear coefficients of the HIPIMS CrN films of 2.3×10⁻¹⁶ m³ N⁻¹ m⁻¹ were lower by a factor of 4 and the roughness of the wear track was significantly reduced compared to the UBM-deposited CrN. The abrasive wear coefficient of the HIPIMS coating was 2.2×10⁻¹³ m³ N⁻¹ m⁻¹ representing an improvement by a factor of 3 over UBM deposited CrN and a wear resistance comparable to that of the superlattice CrN/NbN. The adhesion of the HIPIMS deposited CrN was comparable to state-of-the-art ABS technology.     

Corrosion behavior of nanolayered TiN/NbN multilayer coatings prepared by reactive direct current magnetron sputtering process

TiN, NbN and TiN/NbN multilayer coatings were deposited on tool steel substrates using a reactive DC magnetron sputtering process. The coatings were characterized using X-ray diffraction, nanoindentation, atomic force microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray analysis. The corrosion behavior of TiN/NbN multilayer coatings was studied in 0.5 M HCl and 0.5 M NaCl solutions using potentiodynamic polarization and compared with single layered TiN and NbN coatings. Approximately 1.5 μm thick coatings of TiN, NbN and TiN/NbN multilayers showed good corrosion protection of the tool steel substrate and multilayer coatings performed better than single layered coatings. The corrosion behavior of the multilayers improved with total number of interfaces in the coatings. In order to conclusively demonstrate the positive effect of layering, corrosion behavior of 40-layer TiN/NbN multilayers was studied at lower coating thicknesses (32–200 nm) and compared with single layer TiN coatings of similar thicknesses. The polarization data and SEM studies of these coatings indicated that the corrosion behavior improved with coating thickness and multilayers showed better corrosion resistance as compared to the single layer coatings. Other studies such as intrinsic corrosion, effects of Ti interlayer and post-deposition annealing on the corrosion behavior of the multilayer coatings are also presented in this paper. The results of this study demonstrate that nanolayered multilayers can effectively improve the corrosion behavior of transition metal nitride hard coatings.     

镁合金预处理对其表面有机涂层耐蚀性的影响

镁合金压铸件上涂覆有机涂层后的耐蚀性能与其涂装前的表面处理状态有着密切关系.采用中性盐雾试验和盐水浸渍法对经喷砂、打磨、无铬化学转化、微弧氧化4种不同表面预处理后的丙烯酸树脂涂层进行了耐蚀性测试.结果表明:采用合适的预处理能显著提高涂层的耐蚀性能,其中微弧氧化涂层耐蚀性最佳,在盐雾和盐水浸渍试验中失效时间分别达96 h和168 h;预处理后基材表面光滑的涂层失效形式以起泡为主,而具有微孔或粗糙表面的涂层则以点蚀为主.     

CrN和CrNiN涂层在模拟质子交换膜燃料电池环境中的电化学性能及疏水性能EI北大核心CSCD

用闭合场非平衡磁控溅射离子镀在304不锈钢表面沉积CrN和CrNiN涂层。采用X射线衍射和场发射扫描电镜表征涂层的结构和形貌。采用电化学测试、界面接触电阻测试以及疏水性测试等方法,研究两种不同涂层在模拟质子交换膜燃料电池(Proton Exchange Membrane Fuel Cell,PEMFC)环境下的电化学腐蚀性能、界面接触电阻以及疏水性能。结果表明:CrN涂层主要包含CrN和Cr2N相,CrNiN涂层中CrN和Cr2N相较少,Ni在CrNiN涂层中以单质形式存在;动态极化测试表明涂层的耐蚀性能较好,其中CrNiN涂层的耐蚀性能较CrN涂层差,恒电位极化测试表明CrN和CrNiN涂层的电流密度相当;CrN和CrNiN涂层都显著降低了304不锈钢的界面接触电阻,其中CrN涂层的接触电阻最小;CrNiN涂层疏水性能优于CrN涂层,更有利于质子交换膜燃料电池中的水管理。     

Analysis on microstructure and characteristics of TiAlN/CrN nano-multilayer films deposited by cathodic arc deposition

In this study, TiAlN/CrN multilayer thin films were deposited on SUS 403 stainless steel by cathodic arc deposition. The effects of substrate orientation (substrate surface parallel/perpendicular to target surface) and rotation speed were investigated in detail. Microstructure of the coatings was analyzed by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. Meanwhile, tribological and corrosion tests were performed. The experimental results showed that the as-deposited films exhibit a nano-scale multilayer structure consisting of TiAlN and CrN phases. The TiAlN/CrN multilayer films prepared by a parallel orientation and a rotation speed of 4 rpm not only possesses the best coating hardness and hardness/elastic modulus ratio, but also reveals superior abrasion resistance and corrosion resistance.     

电弧离子镀制备(TiCr)N薄膜的微观结构及性能

利用电弧离子镀 (ArcIonPlating)方法 ,通过对独立的Ti靶和Cr靶的弧电流进行控制 ,成功地在高速钢 (HSS)基体上制备了不同成分配比的 (TiCr)N薄膜。采用X射线衍射 (XRD)分析显示 :薄膜为单一的fcc的结构、没有TiN或CrN相存在 ;薄膜呈 (2 2 0 )结构 ,薄膜的晶格常数随着Cr含量的增加而减小。透射电子显微镜 (TEM)结果表明 :(TiCr)N薄膜的晶粒尺度为2 0nm左右。显微硬度测试表明 :薄膜具有很高的硬度 ,而且随弧流比的变化 ,硬度值有一极大值。同时 ,本文探讨了 (TiCr)N薄膜的宏观残余应力、显微硬度和Cr含量之间的关系及其微观机制     

AZ91D镁合金电偶腐蚀的扫描开尔文探针原位表征

AZ91D镁合金在潮湿、含C1-大气环境中会发生严重的电偶腐蚀.对AZ91D镁合金与Q235碳钢偶接试样在中性盐雾条件下进行了电偶腐蚀试验,利用扫描开尔文探针技术(SKP)原位测量了不同盐雾试验时间后两偶合件表面伏打电位的变化规律.结果表明:由于AZ91D镁合金与Q235碳钢偶接试样存在较大的伏打电位差(约为-1.14...     

两种AC-HVAF喷涂WC涂层微观组织以及耐蚀性研究

利用AC-HAVF喷涂技术在0Cr13Ni5Mo不锈钢上制备了WC-10Co-4Cr,WC-12Co涂层,并利用XRD,SEM,电化学以及盐雾实验分析了涂层的微观组织以及耐蚀性.结果表明:两种涂层相组成与其粉末一致,未出现其他喷涂技术普遍存在的W2C以及W,AC-HAVF喷涂技术可以有效的抑制WC的分解;两种涂层都很致密且与基体结合良好,孔隙率低;电化学以及盐雾实验发现,WC-10Co-4Cr涂层的耐蚀性好于WC-12Co涂层,并较基体0Cr13Ni5Mo不锈钢有较大的提高,粘结相中Cr元素的加入以及孔隙率低是WC-10Co-4Cr涂层耐蚀性优异的重要原因.     

Conducting polyaniline nanoparticles and their dispersion for waterborne corrosion protection coatings

A novel approach for preparing waterborne corrosion protection polyaniline (PANI)-containing coatings was developed. First, conducting polyaniline/partially phosphorylated poly(vinyl alcohol) (PANI/P-PVA) spherical nanoparticles with significant dispersibility in aqueous media were prepared by the chemical oxidative dispersion polymerization in presence of partially phosphorylated poly(vinyl alcohol) (P-PVA). The PANI/P-PVA-containing coatings with different PANI/P-PVA contents were then prepared, employing waterborne epoxy resin as the matrix. The corrosion protection property of PANI/P-PVA-containing coatings on mild steel was investigated by salt spray test and electrochemical impedance spectroscopy (EIS) technique in 3.0 wt % NaCl aqueous solution. The results indicated that the waterborne PANI/P-PVA-containing coatings (PANI/P-PVA content, 2.5 wt %) could offer high protection because the impedance values remained at higher than 1 × 10(7) Ω cm(2) after 30 days of salt spray tests. All the results were compared with these of the waterborne coatings containing PANI nanoparticles in the emeraldine salt form (PANI ES), and the protection mechanism was also proposed with the evidence of scanning electron microscope (SEM) and X-ray photoelectron spectrometry (XPS).     

Verschleiß- und Korrosionsschutz durch Chrom und Chromnitrid (PVD-Abscheidung auf Al und Mg)

Wear and corrosion protection using Cr and CrN (PVD coating on Al and Mg) Investigations of the wear behaviour of uncoated Magnesium and Aluminium alloys (AZ 91hp, AlSi 7Mg) are showing very high wear rates of these materials. To improve the wear behaviour both materials were coated with 9 μm CrN using PVD (Physical Vapour Deposition) technology. The tribological behaviour of the coated light metals was tested afterwards by using a plate on cylinder tribometer. Looking at the results, wear is reduced enormously. The great number of defects in the coating of the magnesium alloy is showing almost no influence to the wear behaviour. The corrosion behaviour of chromium and chromium nitride coatings was tested on the magnesium alloy. Because of the defects in the coating, caused by defects like pores in the magnesium, only a short term protection of the alloy can be achieved. The corrosion behaviour of multilayer coatings is better than the behaviour of single layer coatings.     

电弧离子镀TiN及其复合膜的腐蚀机理探讨

利用电弧离子镀在高速钢基体上制备了TiN及其复合膜（Ti，Cr）N，通过盐水全浸泡试验测量了薄膜的腐蚀速率。利用SEM观察了薄膜腐蚀后的表面形貌及断口形貌，并用其自带的能谱分析仪测量复合膜中Cr的含量，讨论了带有宏观熔滴颗粒的TiN及其复合膜（Ti，Cr）N的腐蚀机理。结果表明：高速钢表面电弧离子镀TiN和（Ti，Cr）N复合膜均可提高其耐腐蚀性能，薄膜的腐蚀主要有小孔腐蚀、缝隙腐蚀及电偶腐蚀。     

Corrosion protection of CrN/TiN multi-coating for bipolar plate of polymer electrolyte membrane fuel cell

The electrochemical corrosion cells will be generated from the possible pinholes of the promising CrN and TiN coatings in a PEMFC environment. To prevent the elution of possible pinholes, CrN/TiN multi-coatings on SS have been considered. This study examined the electrochemical behavior of three CrN/TiN coatings on 316L stainless steel deposited at different CrN/TiN thickness ratios by rf-magnetron sputtering as potential bipolar plate materials. Potentiodynamic tests of CrN/TiN-coated 316L stainless steel carried out in a 1 M H₂SO₄ + 2 ppm HF solution at 70 °C revealed a significantly lower corrosion current density than that of uncoated 316L SS, as well as a decrease in the corrosion current density with decreasing inner-layer CrN thickness. Electrochemical impedance spectroscopy also showed that the CrN/TiN-coated 316L SS sample had higher charge transfer resistance than the uncoated 316L SS sample, which increased with decreasing inner-layer CrN thickness. This was attributed to the crystalline-refined CrN/TiN(200).     

Electrochemical behaviour of chromium nitride coatings with various preferred orientations deposited on steel by unbalanced magnetron sputtering

Abstract

Chromium nitride coatings Cr₂N(111) and preferred orientations of CrN(111) and CrN(200) were successfully deposited on AISI 304 stainless steel by an unbalanced magnetron sputtering method. The electrochemical corrosion properties of the deposited films were studied in a 0·5M H₂SO₄ + 1M NaCl aqueous solution at ambient temperature by electrochemical measurements, including the corrosion potential E _corr, linear polarisation, potentiodynamic polarisation and electrochemical impedance spectroscopy. The structural characterisation and surface morphology were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. The experimental results indicated that the CrN(200) coating possesses the best corrosion resistance property, followed by the CrN(111) coating, while the Cr₂N coating has the least resistance among the three types of CrN(111), CrN(200) and Cr₂N(111) coatings. The porosity, corresponding to the ratio of the polarisation resistance of the uncoated and the coated substrates, was higher in the Cr₂N(111) coating than in the other CrN coatings. The CrN(200) coating had a dense microstructure almost without porosity. The void defects of CrN(111) and Cr₂N(111) coatings are responsible for the decrease in corrosion protection.     

Hardness and nitrogen bonding structure of AlxTi1-xN/CrN multilayer hard coating

AlxTi1-xN/CrN multilayer coatings were fabricated by magnetron sputtering and those hardness variations were studied by observing the crack propagation and measuring the chemical bonding state of nitrides by Ti addition. While AlN/CrN multilayer shown stair-like crack propagation, AlxTi1-xN/CrN multilayer illustrated straight crack propagation. Most interestingly, Ti addition induced more broken nitrogen bonds in the nitride multilayers, leading to the reduction of hardness. However, the hardness of Al0.25Ti0.75N/CrN multilayer, having high Ti contents, increased by the formation of many Ti-N bond again instead of Al-N bond. From these results, we found that linear crack propagation behavior was dominated by broken nitrogen bonds in the AlxTi1-xN/CrN multilayer coatings.     

封孔处理对等离子喷涂Cr2O3-8TiO2涂层耐腐蚀性能的影响

为了提高等离子喷涂陶瓷涂层的耐腐蚀性能,扩大其应用范围,以环氧树脂和有机硅树脂为封孔剂对等离子喷涂Cr2O3-8TiO2涂层进行了封孔处理,采用盐雾腐蚀和电化学腐蚀方法对封孔涂层和未封孔涂层的耐腐蚀性能进行研究,使用扫描电镜/能谱仪(SEM/EDS)、光学显微镜(OM)观察了腐蚀前后涂层的形貌及成分变化,分析涂层的腐蚀机理.结果表明,240h盐雾腐蚀后未封孔涂层发生剥落失效,而有机硅树脂封孔涂层经1200h盐雾腐蚀表面仍保持完好.封孔涂层的耐腐蚀性明显优于未封孔涂层,有机硅树脂的封孔效果优于环氧树脂.     

离子镀硬质膜技术的最新进展和展望

电弧离子镀至今仍是硬质膜的主流技术,但是,其内容与８０年代比已大为丰富。首先,镀层材料由单一氮化钛,发展到氮化钛与碳氮化钛,氮化钛铝,氮化铬等多种材料并用。然后,又进一步发展为多层复合镀层。远离平衡态过程听低温沉积技术日趋成熟。使各种机械零件的需磨损磨腐蚀底层逐步走向实用化,促进了机械戒严水平全面提高。低温沉积技术大幅度降低镀层内应力,使镀层的厚度能够达到数十,甚至上百微米,满足了发展高性能特性镀     

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.     

Influence of the HVOF spraying process on the microstructure and corrosion behaviour of Ni-20%Cr coatings

The microstructure and the aqueous corrosion resistance of coatings produced by High Velocity Oxy-Fuel (HVOF) spraying techniques has been investigated. Two types of spraying processes have been employed i.e., Topgun HVOF using propylene gas and Met-Jet II HVOF with kerosene liquid fuel together with two forms of Ni-20%Cr powders i.e., water and inert gas atomised. The oxide, porosity and the amount of melted material in the coatings were characterised using scanning electron microscopy (SEM) and X-ray diffraction (XRD), whilst the corrosion resistance of the coatings and the ability to protect the underlying mild steel substrate was evaluated by use of a salt spray chamber and potentiodynamic tests.MetJet II produced coatings from gas-atomised powder with a lower oxide content, a reduction in porosity and less melted material, as the residence time of particles in the combusted gas stream was shortened. Water atomised powder formed a higher volume fractions of unmelted material and porosity when compared with gas-atomised powder coatings. This was encouraged by the presence of a thin oxide layer, which formed during the production of the water-atomised powder. The orientation of oxides and pores in the coatings had a major effect on their aqueous corrosion behaviour. Better protection for the underlying steel substrate (>3000 h exposure in a salt spray test) was obtained with the coating produced from the gas-atomised powder with the MetJet II system, which had the lowest porosity/oxide content running perpendicular to the substrate surface. The major factor in preventing attack on the mild steel substrate is the amount of interconnecting porosity which allows the corrodant to percolate through the coating.     

Filter effects on the wear and corrosion behaviors of arc deposited (Ti,Al)N coatings for application on cold-work tool steel

In this study, (Ti,Al)N coatings were deposited on Japanese Industrial Standard SKD11 modified cold-work tool steel using a cathodic arc deposition system with and without magnetic filter attachment. Coating morphology and properties such as coating structure, adhesion, hardness, abrasion and corrosion behaviors were analyzed to evaluate the effects of magnetic filter on the coatings. The results showed that magnetic filtering slowed down (Ti,Al)N deposition rate, but it improved component homogeneity, roughness and adhesion of the coatings. Although (Ti,Al)N coated specimens produced with or without filter both showed superior abrasion resistance in service, however, filtered (Ti,Al)N coatings yielded better corrosion protection of the steel than unfiltered ones in 3.5 wt.% NaCl aqueous medium.     

ZK61S镁合金微弧氧化膜层的结构及耐腐蚀性能

为了提高ZK61S镁合金的耐腐蚀性能,采用微弧氧化方法以不同电压(300,380,450 V)在ZK61S镁合金表面制备氧化膜并进行封孔处理。利用金相显微镜、扫描电镜、X射线衍射仪分析膜层的形貌、结构和组成;通过腐蚀电位试验、中性盐雾腐蚀试验及抗剥落腐蚀试验进行耐腐蚀性能考核。结果表明:微弧氧化呈现疏松多孔形态且均匀覆盖于基材表面,主要由Mg、MgO和Al_2Si_2O_5(OH)4相组成;微弧氧化处理后试样的腐蚀电位显著提升,且380 V所得微弧氧化试板的腐蚀电位达到-881.53 m V,经过408 h的中性盐雾腐蚀试验后的腐蚀速率为0.012g/(m~2·h),耐蚀性能比未进行表面处理的基材提高了88倍;经封孔处理的微弧氧化试板经过456 h的中性盐雾腐蚀试验后腐蚀速率降低到0.003 g/(m~2·h);封孔处理使微弧氧化膜的抗剥落腐蚀性能由微弧氧化后的EB级提升到EA级。