轮胎模具无氢DLC涂层的制备及表征

为探究轮胎模具类金刚石(DLC)涂层的应用前景,提高模具表面的硬度和疏水性,按照模具加工工艺制备35钢基体试样,利用电弧离子镀在基体上沉积无氢DLC涂层,对涂层粗糙度、三维表面形貌、断面结构、元素组成及含量、Raman光谱、纳米硬度和疏水性进行了分析.结果表明:通过改变粗糙度可以改善涂层的疏水性,涂层疏水性随粗糙度增大而显著增加,水接触角最高可达96°,且涂层硬度可达30.3 GPa.无氢DLC涂层可满足轮胎模具耐磨性和易清洁的使用要求,为制造高性能轮胎模具提供了一种可行的工艺选择.     

Microstructural characterisation of nanocomposite nc-MeC/a-C coatings on oxygen hardened Ti-6Al-4V alloy

Nanocomposite coatings are novel, important systems composed of two or more nanocrystalline, or nanocrystalline and amorphous, phases. Such coatings offer a possibility of tailoring the coating microstructure and achieving new improved properties of coated materials. In this work a duplex surface treatment, consisting of an oxygen diffusion treatment and deposition of low friction nanocomposite nc-MeC/a-C (Me = transition metal, Ti, W or Cr) coatings, was applied for improvement of the Ti-6Al-4V alloy properties. The coatings composed of nanocrystallites of transition metal carbides (TiC or Cr_xC_y or WC) embedded in hydrogen-free amorphous carbon (a-C) matrix were deposited onto the surface of an oxygen hardened Ti-6Al-4 V alloy substrate by means of a simple DC magnetron sputtering. A nano/microstructure of the substrate material and coatings has been examined by scanning- and transmission electron microscopy complemented with the results of X-ray diffraction analyses.It was found that the nanocomposite coatings are composed of different carbide nanocrystals (with sizes of a few nanometres) embedded in an amorphous carbon matrix. The results of qualitative and quantitative analyses of the nanocrystalline phase in the coatings with use of high-resolution transmission electron microscopy combined with image analysis are given in the paper.An effect of the nano/microstructure parameters of the coated alloy onto its micro-mechanical (nanohardness and Young's modulus) and tribological properties (wear resistance and friction coefficient) is discussed in the paper.     

非平衡磁控溅射技术制备用于红外减反射的无氢碳膜

红外减反射保护膜具有特定的厚度要求,如能进一步减小无氢类金刚石膜(DLC)的光学吸收,就能使其在较大厚度时不过分损失光通量而得以广泛应用.从这点来讲,无氢类金刚石膜是一种极具开发潜力的材料.本文采用非平衡磁控溅射技术(UBMS)制备了无氢类金刚石膜,并研究了其厚度均匀性.研究结果表明:该非平衡磁控溅射装置有能力获得大于φ150 mm的均匀性范围.对DLC膜红外透射谱的分析表明,分别在Si和Ge基底表面单面制备的DLC薄膜,其峰值透射率在波数2983/cm时分别为68.83%和63.05%,这一结果接近无吸收碳材料理论上所能达到的值.同时,在5000到800/cm范围内,未发现明显的吸收峰.这些优良的光学特性表明,采用非平衡磁控溅射技术制备的无氢DLC膜可以作为窗口的红外增透保护膜使用.     

Electrical percolation threshold in Ag–DLC nanocomposite films prepared by RF-sputtering and RF-PECVD in acetylene plasma

Silver–diamond like carbon (Ag–DLC) nanocomposite films were deposited on glass and silicon substrates by co-deposition of RF-sputtering and RF-PECVD method in acetylene plasma. The effects of deposition time on creation of conductive percolation pathway in Ag–DLC nanocomposite films were investigated. The films were characterized by XRD pattern, AFM images, UV–Vis and FTIR spectra. Pressure of chamber’s variation over time was illustrated the rate of carbon and silver deposition changing. The results showed that nanoparticles’ size and surface roughness was increased by increasing deposition time. Surface plasmon resonance peak’s red shift in optical absorption spectra of samples could be depends on silver nanoparticles’ scale up. Based on electrical measurements, electrical percolation threshold was observed only in the film with 35 min deposition time. Pathway was created for electric current by Ag nanoparticles’ moving in carbon matrix due to sp³ bonds and silver content in the films. The aging effect was studied for sample #2 in the threshold of percolation, where obtained Ag nanoparticles memorize its previous pathway. This investigation provides a better understanding for electric properties of Ag–DLC nanocomposite based on the percolation theory.     

Ag surface diffusion and out-of-bulk segregation in CrN-Ag nano-composite coatings

CrN-Ag nanocomposite coatings are deposited on Si(100) wafers and 20MnCr5 steel disks in a mixed Ar+N2 atmosphere by reactive magnetron sputtering. Structure, composition and morphology were investigated by Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES), X-ray Photoemission Spectroscopy (XPS), X-ray Diffraction (XRD) and Focused Ion Beam (FIB) cross sectional analysis. The as deposited film matrix is mainly composed by CrN phase (78%), but a relevant part (28%) is composed by Cr2N. Ag agglomerates in the CrN matrix forming elongated grains 200-400 nm wide and 50-100 nm high, which extends on the top of CrN columns. At the surface Ag aggregates into two different structures: large tetrahedral crystalline clusters, with typical dimension ranging from 200 to 500 nm, and smaller Ag nanoparticles with diameter of 15-25 nm. The annealing in N2 atmosphere up to 500 degrees C does not affect size and distribution of the Ag grains in the sub-surface region, while it induces a size increase of the bigger Ag clusters on the surface, mainly related to Ag surface diffusion and clusters coalescence. Annealing at higher temperature leads to an evident Ag out-of-bulk segregation, generating Ag depleted voids in the near-surface region, and further increasing of the Ag clusters size at the surface. Tribological tests on as deposited CrN-Ag film reveal a coefficient of friction against a steel ball reduced with respect to CrN film, probably related to the presence of Ag which acts as solid lubricant, but the coating is removed after a very short sliding distance. The poor mechanical properties of the realized Ag-based coatings are confirmed by lower hardness and Young modulus values with respect to pure CrN.     

Corrosion protection of carbon fibre reinforced aluminium composite by diamondlike carbon coatings

Abstract

Carbon fibre reinforced aluminium exhibits poor resistance against electrochemical corrosion in 3·5 wt-%NaCl solution. Diamondlike carbon (DLC) coatings provide properties which make them interesting materials for external corrosion protection on metal matrix composites (MMCs). The electrochemical corrosion behaviour of uncoated and DLC coated carbon fibre reinforced aluminium was tested in 3·5 wt-%NaCl solution. It has been found that the pitting potential is shifted significantly in the anodic direction and the corrosion current density is much lower due to the presence of the sealing DLC coating. Additionally, scratch tests and SEM studies were carried out in order to characterise the adhesion of the DLC films on the heterogeneous MMCs. Reliable corrosion protection is connected with sufficient coating durability under loading. In order to ensure sufficient loading capacity of the DLC coating under tribological conditions, wear tests were undertaken which revealed a considerable improvement in wear resistance due to deposition of the DLC coatings.     

Study of (Zr,Ti)CN, (Zr,Hf)CN and (Zr,Nb)CN films prepared by reactive magnetron sputtering

(Zr,Ti)CN, (Zr,Hf)CN and (Zr,Nb)CN coatings, in which Ti, Hf and Nb were added to ZrCN base compound, have been prepared by reactive magnetron sputtering. The coatings, with two different non-metal/metal ratios, were comparatively investigated in terms of elemental and phase composition, texture, surface morphology, hardness and friction performance. It has been shown that the films exhibit nanocomposite structures, consisting of a mixture of crystalline metal carbonitride and amorphous carbon. As compared with ternary ZrCN coatings, the quaternary coatings were found to exhibit superior mechanical and friction characteristics. In general, the films with higher non-metal content revealed finer morphologies, higher hardness and lower friction coefficient. Depending on the coating type and non-metal/metal ratio, the hardness values ranged from about 21 to 29 GPa, being higher than those of ZrCN reference films. The coefficients of friction varied from 0.2 to 0.5, the lowest values being obtained for the coatings with the highest non-metal content.     

Influence of multi-interfacial structure on mechanical and tribological properties of TiSiN/Ag multilayer coatings

The TiSiN/Ag multilayer coatings with bilayer periods of ~50, 65, 80, 115, 150, and 410 nm have been deposited on Ti6Al4 V alloy by arc ion plating. In order to improve the adhesion of the TiSiN/Ag multilayer coatings, TiN buffer layer was first deposited on titanium alloy. The multi-interfacial TiSiN/Ag layers possess alternating TiSiN and Ag layers. The TiSiN layers display a typical nanocrystalline/amorphous microstructure, with nanocrystalline TiN and amorphous Si₃N₄. TiN nanocrystallites embed in amorphous Si₃N₄ matrix exhibiting a fine-grained crystalline structure. The Ag layers exhibit ductile nanocrystalline metallic silver. The coatings appear to be a strong TiN (200)-preferred orientation for fiber texture growth. Moreover, the grain size of TiN decreases with the decrease of the bilayer periods. Evidence concluded from transmission electron microscopy revealed that multi-interfacial structures effectively limit continuous growth of single (200)-preferred orientation coarse columnar TiN crystals. The hardness of the coatings increases with the decreasing bilayer periods. Multi-interface can act as a lubricant, effectively hinder the cracks propagation and prevent aggressive seawater from permeating to substrate through the micro-pores to some extent, reducing the friction coefficient and wear rates. It was found that the TiSiN/Ag multilayer coating with a bilayer period of 50 nm shows an excellent wear resistance due to the fine grain size, high hardness, and silver-lubricated transfer films formed during wear tests.     

非平衡磁控溅射类金刚石碳膜的性能

用非平衡磁控溅射的方法在室温下制备了光滑、均匀、致密的类金刚石(DLC)薄膜,分析和研究了DLC膜的形貌、结构和摩擦特性.结果表明,靶工作电流对DLC膜的沉积有重要的影响.随着工作电流的增大,薄膜的沉积速率增大,薄膜中sp3键的含量增加.薄膜的摩擦系数随着工作电流的增加略有增大,在摩擦的初始阶段,摩擦系数较高,随着摩擦循环次数的增加,摩擦系数逐渐减小,并逐渐趋于稳定.     

Effects of natural aging and heat treatments conditions on mechanical properties of dissimilar composite between 6061 Al alloy and Al-Si12CuNi (AC8A) Al cast alloy fabricated by friction welding

This paper describes the effects of natural aging and heat treatments conditions on mechanical properties of dissimilar composite between 6061 Al alloy (AA6061) and Al-Si12CuNi (AC8A) Al cast alloy, which was fabricated by friction welding. The dissimilar composite was composed of specimens with the pipe part which had an outer diameter of 30.0 mm and an inner diameter of 24.0 mm. This composite had the softened region at the adjacent region of the interface of both materials. The softened region of both sides of the composite recovered the hardness with increasing natural aging time, and those with a natural aging time of 35 days (1 month) or longer had almost similar softened region. Then, the composite with a natural aging time of 35 days (AW composite) had approximately 62% in the tensile strength of the AC8A base metal. The fractured point was the adjacent region of the interface at the AC8A side, i.e. the softened region. The softened region of AW composites, which were re-treated with T6 condition of each base metal, was also recovered. Those composites had approximately 58% in the tensile strength of the AC8A base metal, and those fractured from the corner part of the inner diameter in the AC8A side. In addition, the composite with the high temperature environment with a heating temperature of 473 K, which was re-treated with T6 condition of the AC8A base metal, fractured from the corner part of the inner diameter in the AC8A side. That is, the interface of the composite tightly joined. The possibility that can use the composite fabricated by friction welding as an engine piston was obtained by experimental approach, because the composite did not have the fracture from the interface.     

Supertough wear-resistant coatings with ‘chameleon’ surface adaptation

The chameleon's ability to change skin color depending on environment to increase its chances of surviving served as an inspiration in the development of self-adaptive supertough wear-resistant coatings. Surface chemistry, structure and mechanical properties of these thin (0.5 μm) coatings reversibly change with applied load and environment, providing the best wear protection. Coating designs developed in-house are reviewed together with a critical analysis of design reports in the literature. ‘Chameleon’ coatings were prepared using novel nanocomposite structures, consisting of crystalline carbides, diamond-like carbon (DLC), and transition metal dichalcogenides. Various mechanisms were activated to achieve surface self-adaptation and supertough characteristics. They included: transition of mechanical response from hard and rigid to quasi plastic by grain boundary sliding at loads above the elastic limit; friction induced sp³→sp² phase transition of the DLC phase; re-crystallization and reorientation of the dichalcogenide phase; change of surface chemistry and structure from amorphous carbon in humid air to hexagonal dichalcogenide in dry nitrogen and vacuum; and sealing the dichalcogenide phase to prevent oxidation. These mechanisms were demonstrated using WC/DLC, TiC/DLC, and WC/DLC/WS₂ coatings. The hardness of WC/DLC and TiC/DLC composites was between 27–32 GPa and scratch toughness was 4–5 fold above that of nanocrystalline carbides. The WC/DLC/WS₂ composites survived millions of sliding cycles in vacuum and air under 500–1000 MPa loading, and exhibited excellent friction recovery in humid↔dry environmental cycling. Their friction coefficients were about 0.1 in humid air, 0.03 in vacuum, and as low as 0.007 in dry nitrogen. The proposed ‘chameleon’ concept can dramatically increase wear-resistant coating applicability, durability, and reliability.     

Tribological behavior of nanocomposite coatings based on fullerene-like structures

This paper presents a new group of nanocomposite coatings based on integrating inorganic fullerene-like material (IFLM) structures into conventional coating matrices. Such coatings have been developed within the scope of the European funded FOREMOST project (FP6-NMP3-CT-2005-515840).Regarding the synthesis of these nanocomposite coatings based on fullerene-like components, two alternative routes were explored: introducing preformed IFLMs into the coating deposition process or forming the fullerene-like components in situ during the coating deposition process. Both methods have been demonstrated to be technically feasible, depending on the nature of the coating matrix or the desired fullerene-like structure.These new materials allow some independent control of tribological properties usually known as antagonists (very high load bearing capacity with a very low friction coefficient). In the case of unidirectional movement, under dry conditions, the best coatings developed in FOREMOST displayed a coefficient of friction in air within the range 0.04-0.10, depending on the degree of humidity and the test conditions. Pure sliding laboratory tests indicate that for some industrial applications fullerene-like nanocomposite coatings can give significant reductions in wear and friction coefficient when compared to similar coatings without fullerene-like components. The lubrication mechanisms through which these fullerene-like structures improve friction and prevent wear are also discussed in this paper.     

Minderung von Reibung und Verschleiß von Bauteilen aus Aluminium mit diamantähnlichen Kohlenstoffschichten (DLC)

Reduction of friction and wear for parts made of aluminium by diamond-like carbon coatings Reduction of friction and wear of machine parts and tools is usually achieved by separating the participating surfaces. This is predominantly done by liquid lubricants. Solid lubricant coatings replace them where hydrodynamic lubrication is not possible or not active. Among the hard and friction reducing layers diamond-like carbon films (DLC) have distinguished themselves as the most interesting representatives. They are deposited on metallic and ceramic parts in a glow discharge of a hydrocarbon gas at temperatures between 150 and 200 °C. Those low deposition temperatures, their very low dry sliding friction coefficient of 0.05 to 0.1, and an elastic recovery of 90 % differentiate them from PVD coatings to a high degree. DLC can also be deposited on light metals with thicknesses of more than 30 μm. For closed films an outstanding protection against corrosion is established. Machining and forming of light metals can be done without cooling lubricants.     

基于LFM的类金刚石膜纳米摩擦现象研究

使用原子力显微镜(AFM)中的侧向力(LFM)模式对类金刚石膜纳米尺度的摩擦现象进行了研究,主要考察了载荷、微观形貌、粘附对类金刚石膜纳米摩擦性能的影响.首先结合粘附的影响提出了适用于外加载荷在100 nN以下类金刚石膜纳米摩擦力表征的修正Amonton公式.其次,试验发现摩擦过程中表面接触峰的斜率对薄膜的微观摩擦力的影响较大,微观摩擦系数与倾角θ成正比例关系,最后结合两者给出了综合考虑载荷、表面形貌、粘附且可用于类金刚石膜纳米尺度摩擦力表征的数学方法.     

Development and Characterization of Zr‐Based Multi‐Component Nanocomposite Coatings Prepared Using Single Alloying Target

Nanocomposite coatings comprising multiple phases on the nanoscale are increasingly used for automobile engine systems as they offer high thermal stability, high hardness, and low coefficient of friction. Since it is not easy to fabricate alloying targets, multiple targets have been used to prepare conventional nanocomposite coatings, resulting in the need for complex equipment and processes. Therefore, single alloying targets with homogeneous compositions and high toughness will simplify mass production of nanocomposite coatings. In this study, amorphous alloys are introduced to prepare the alloying target because of their homogeneous composition, good mechanical properties, and design rules that are similar to those for nanocomposites. Multi‐component alloying targets comprising Zr, Al, Mo, and Cu are successfully prepared by atomization and spark plasma sintering, both of which are powder metallurgical processes. The targets with amorphous structure are subsequently heat‐treated in a vacuum at ≈800 °C to crystallize the microstructure and improve the mechanical properties for sputtering. This study is the first report on modification of the fracture toughness of Zr‐based intermetallic compounds by changing the grain size. Improved fracture toughness of these compounds with a specific range of grain size is obtained by heat treatment of the amorphous target.

     

Nano /spl alpha/-Fe/epoxy resin composite absorber coatings fabricated by thermal spraying technique

In this paper, the low temperature high velocity air fuel (LTHVAF) spraying technique was applied to prepare the /spl alpha/-Fe/epoxy resin nanocomposite coatings. The composite powders were mixed with different mass fractions, and the microstructure and reflectivity coefficient of coatings were tested. The results show that the microstructure of coatings is dense and low porosity; nano metal particles are dispersed in the coatings. The coatings are closely combined with substrate. In these coatings, the volume fraction calculated with density, component distribution, properties of metal particle, and coating thickness can affect the microwave absorption ability of the coatings. The reflectance coefficient of 70 mass% nano /spl alpha/-Fe/epoxy resin composite coatings is lower than others. In these nanocompsite absorber coatings, the relationship of the reflectivity coefficient and the coating structure were constructed with permittivity, permeability, and thickness. The optimal mass fraction of absorber coatings is about 0.3. It is analyzed with self-bonding strength and reflectivity coefficient. This means that the change of the coating structure affects the performance of the nanocomposite coatings.     

超声处理对建筑用EVM表面离子镀DLC涂层组织和摩擦性的影响

通过超声方法处理聚氨基甲酸酯表面,选择脉冲碳离子源,结合阴极放电等离子方法在EVM表面完成DLC涂层的沉积过程,对超声处理过程中温度与时间参数引起的DLC涂层摩擦特性改变进行分析.实验测试研究结果表明:当超声处理的时间延长或者温度升高后,在试样表面形成了更深的条纹,能够显著增强EVM表面发生溶解的能力.DLC涂层在拉曼...     

Study on tribological behavior of electrodeposited Cu–Si3N4 composite coatings

Cu–Si₃N₄ composite coatings were prepared by electrolysis from a copper sulphate solution containing dispersed Si₃N₄ particles of 0.4 or 1 μm mean size. Wear behavior of Cu–Si₃N₄ composite and pure copper coatings were evaluated using a pin-on-disc test machine under dry condition sliding. Effects of current density and particle concentration on the incorporation percentage of Si₃N₄, the preferred orientation of copper crystallites, the microstructure, the microhardness and the wear resistance of the coatings were determined. Si₃N₄ particles in the copper matrix resulted in the production of composite deposits with smaller grain sizes and led to change the preferred orientation growth from [1 0 0] to [1 1 0]. It was proved that the presence of Si₃N₄ particles decreases the wear loss and the friction coefficient of the coating. According to the results, the friction coefficient decreased dramatically from 0.52 to 0.26 for pure copper coatings to 0.16–0.24 for Cu–Si₃N₄ composite coatings. In addition, fluctuation of friction coefficient values for Cu–Si₃N₄ composite coating was lower compared with the pure copper coating. The wear properties of Cu–Si₃N₄ composite coatings were shown to depend on the weight fraction, the size and the distribution of co-deposited particles.     

Protective Ag:TiO2 thin films for pressure sensors in orthopedic prosthesis: the importance of composition,structural and morphological features on the biological response of the coatings

DC reactive magnetron sputtered Ag:TiO₂ nanocomposite thin films were developed to be used as protective coatings in pressure sensor devices. The coatings, with Ag content varying from 0 to about 30 at.%, were prepared and characterized in order to study their biological response. The as-deposited samples were annealed in vacuum at 500 °C in order to evaluate the influence of their morphological and structural differences over the response elicited upon contact with simulated bodily fluids and cultured human cells, as well as selected microorganisms. The results showed that the annealing treatment produced less porous films with an enhanced structure, with a significant reduction in structural defects and improved crystallinity. Additionally, samples with higher Ag contents (≥12.8 at.%) exhibited Ag agglomerates/clusters at the surface, a result anticipated from the XRD data. The crystallization of the TiO₂ matrix was also observed by XRD analysis, albeit delayed by the dispersion of Ag into the matrix. Biological characterization showed that the antimicrobial activity and cytotoxicity of the coatings were directly related with their composition, closely followed by the particular structural and morphological features, namely those resulting from annealing process.     

Effect of copper nanoparticle addition on the electrical and optical properties of thin films prepared from silver nanoparticles

The fabrication of transparent and conductive silver (Ag) and copper (Cu)-doped Ag films using simple spin-coating method with Ag and Cu nanoparticles (NPs) as starting material is described in this study. The aggregation of Ag NP and the grain formation caused by heat treatment were hindered by the addition of small amount Cu NP, and a continuous film was obtained even though the thickness was in the order of 10 nm. When the total metal concentration of NP solution precursor was 5 wt% with the ratio between Ag and Cu being 95:5, the surface resistivity (ρ _s) of Ag–Cu film was 3.17 Ω/sq; and when the concentration was reduced to 3.5 wt%, the ρ _s was 16.3 Ω/sq. The transmission of latter was more than 60 % with the maximum value 82.1 % at 328 nm in the near-UV region (300–400 nm), however, decreased to about 38 % in the visible region (400–700 nm) and near-IR region. The inhomogeneity of the film increased leading to the decrease of the conductivity with the time extension during the heat treatment.