冷喷涂NiCoCrAlY高温合金防护涂层性能研究

在600℃、2.3 MPa压力和氦气环境下用冷喷涂技术制备了NiCoCrAlY涂层。在600℃下对涂层进行了热处理,用扫描电镜(带能谱仪)、显微硬度测试仪分析了热处理前后涂层微观形貌及显微硬度。结果表明,用冷喷涂技术可以制备出结构致密的NiCoCrAlY涂层,热处理后的涂层变得更加致密,显微硬度有了明显的提高。     

织物用隔热涂层材料及其涂层技术的研究进展

织物用隔热涂层能够在基本不消耗资源的情况下实现织物降温或保温的功能,是一种新型功能性涂层,具有较好的应用前景。综述了国内外织物用隔热涂层的研究方法与应用进展,介绍了其涂层材料以及涂层技术的研究概况,并列举了国内外织物用隔热涂层的部分研究工作,重点对织物用隔热涂层的今后的发展进行了展望。提出了织物用隔热涂层在原材料、涂层技术、测试装置、生产设备以及功能性等方面的研究方向。     

碳纤维表面陶瓷涂层的制备与应用研究

综述了在碳纤维表面涂覆陶瓷涂层的方法,分析了各种涂层方法的优缺点,讨论了用化学气相沉积、溶胶-凝胶、液相浸渍、电泳沉积和电解沉积等技术获得氧化物、碳化物、氮化物、碳氮化物及碳氧化物陶瓷涂层的状况,并指出了单一陶瓷涂层存在的问题及可能的解决途径.     

铌合金表面高温抗氧化涂层

介绍了铌合金表面高温抗氧化涂层的4大体系--耐热合金涂层、铝化物涂层、硅化物涂层和贵金属涂层的组成、特点及制备条件.我国研究人员围绕飞机发动机涡轮叶片和火箭发动机燃烧室及尾气喷管用铌合金的防护进行了大量研究工作,研制的高温抗氧化涂层已经用于49kN推力发动机铌合围裙和姿态控制铌合金喷管.通过研究认为,PVD和传统熔烧工艺相结合的新工艺及纳米涂层技术是今后铌合金表面高温涂层制备的研究方向.     

陶瓷涂层在航空发动机涡轮叶片表面处理中的应用

从涂层材料、制备方法、涂层特点及存在的问题等几个方面介绍了作层技术的研究和发展状况,并针对航空发动机涡轮叶片,在分析了陶瓷涂层作为叶片热障涂层的应用研究状况和效能的同时,提出在叶片易磨损部位的修复中应用陶瓷涂层以及直接用陶瓷涂层作为叶片耐磨涂层的设想。     

对LY12铝合金离子镀氮化钛涂层的增强结合力的研究

在LYl2铝合金上,用离子镀设备进行了增强氮化钛涂层结合力的研究。通过镀前表面处理工艺技术及镀膜过程中控制烘烤温度、加镀过渡层、延长沉积时间等主要工艺技术,最终得到了令人满意的、涂层结合力增强的氮化钛涂层。     

铜合金表面溶胶-凝胶涂层抗腐蚀性能的研究

采用溶胶－凝胶技术,以正硅酸乙酯为基本原料,配制二氧化硅溶液－凝胶液,采用浸涂法在牙科用铜合金表面涂层。用SEM、DTA、ICP等方法对二氧化硅溶胶－凝胶涂层的形貌及特性进行了研究与分析。结果表明,该涂层在乳酸腐蚀液中能减少合金离子的释放,提高了铜合金的抗腐蚀性能,铜合金与涂层的结合中强度可达40MPa。     

热喷涂专用纳米材料及其涂层制备的研究现状

热喷涂纳米涂层的研究是目前纳米涂层领域研究热点之一.综述了国内外热喷涂专用纳米材料的制备方法以及采用几种先进的热喷涂技术制备的纳米涂层,指出了目前用热喷涂技术制备纳米涂层所面临的难题.展望了热喷涂技术在制备纳米涂层方面的发展前景.     

CrNi3MoVA钢表面电火花沉积W-Ni-Fe-Co涂层的摩擦磨损性能

为进一步拓展火炮身管内膛强化手段,采用粉末冶金技术制备了W-Ni-Fe-Co合金,利用电火花表面沉积技术在CrNi3MoVA钢表面沉积了W-Ni-Fe-Co涂层,同时利用电镀技术在CrNi3MoVA钢表面制备了硬Cr涂层与之进行比较,用纳米压痕仪和摩擦磨损试验机研究了涂层的摩擦磨损性能,并利用XRD、SEM和EDS研究了沉积态和磨损后涂层的相结构、形貌及成分。结果表明电火花沉积W-Ni-Fe-Co涂层由α-W、γ-Fe和NiWO4组成,α-W在涂层中呈白亮带分布;W-Ni-Fe-Co涂层的硬度较电镀硬Cr涂层降低了18%,弹性模量较电镀硬Cr涂层提高了4%;W-Ni-Fe-Co涂层的磨损机制为轻微的粘着磨损,而电镀硬Cr涂层为严重的粘着磨损;CrNi3MoVA钢表面沉积W-Ni-Fe-Co涂层较电镀硬Cr涂层具有明显的减摩耐磨效果,随着摩擦速度的增加,W-Ni-Fe-Co涂层的摩擦系数降低,其原因是磨损表面氧化加剧,氧化物的自润滑作用加大。     

纳米TiO_2-WO_3复合涂层及纳米TiO_2/WO_3叠层涂层的制备及性能

为了解决电子池材料改性TiO2涂层暗态下无阴极保护作用的问题,用溶胶-凝胶法及浸渍提拉技术在304不锈钢表面制备了纳米TiO2-WO3复合涂层与纳米TiO2/WO3叠层涂层,用扫描电镜(SEM)、X射线光电子能谱仪(XPS)研究了2种涂层的表面形貌、成分,并用电化学方法研究了2种涂层的光阴极保护特性及耐腐蚀性能。结果表明:2种涂层表面均连续均匀,由Ti,W,O,C组成;紫外光照1 h时2种涂层均对304不锈钢有一定的光阴极保护作用,闭光后纳米TiO2/WO3叠层涂层的延时阴极保护作用远好于纳米TiO2-WO3复合涂层;2种涂层均对304不锈钢有防腐蚀作用,紫外光照射时纳米TiO2-WO3复合涂层的防腐蚀性比纳米TiO2/WO3叠层涂层的好。     

碳纤维与铜、钴、铁等金属的相容性研究

文中针对目前较少报道的有关碳纤维与铜、钴、铁等金属的相容性问题进行了实验研究工作。主要通过采用强度测定、X射线、金相和扫描电镜等方法研究了镀有不同金属的碳纤维经不同温度真空热处理后的镀层形貌、纤维组织结构和强度等方面的变化,提出了一些高温下碳纤维与不同金属之间的相互作用机制。试图为采用铜、钴、铁等金属作为碳纤维的镀层或基体的可能性提供实验和理论分析上的初步依据。      

On the Effects of Surface Treatments on the Mechanical Strength of Carbon Fibres

TiB2, pyrolytic carbon (Cpyr) and Cpyr + TiB2 double layer coatings have been envisaged as potential protective coatings to prevent the deleterious interface reactions between the carbon fibre and the aluminium matrix during composite manufacturing. These coatings have been obtained by low pressure chemical vapour deposition on T800H carbon fibre yarns. In spite of a 20 % increase in the coated monofilaments tensile strength observed for very thin Cpyr coatings, a strength decrease as a function of the coating thickness is recorded for single Cpyr or TiB2 layers. For the TiB2 coatings, this decrease fits well with Ochiai's model which simulates the notch effect induced by a cracked brittle layer. Concerning the Cpyr coatings, a lower damaging effect is observed as compared to TiB2, it may be explained by the difference between the Young's moduli of both layers. Although the initial fibre properties are not perfectly maintained in the case of the double layer, the crack deviation role of the Cpyr coating succeeds in preserving the coated fibres from the TiB2 notch effect, thus leading to a noticeable strength increase.     

Effect of fibre surface morphology on stability of C/TiBx coatings in Ti–6Al–4V/σ (SM1240) fibre metal matrix composite

Abstract

Sigmafibres (SM1240) produced by a chemical vapour deposition process using a 15 μm tungsten wire corefor SiC deposition have a duplex coating of graphitic carbon and TiBx. Nodules present on the fibre surface are attributed to the deposition of the carbon coating over soot particles present on the substrate. Both the carbon and TiB_x coatings were stable in vacuum or air at temperatures up to 973 K. The nodules werefound to be sites of preferential attack by the titanium alloy matrix. The average number of nodules per fibre decreased more rapidly when the specimens were heated in air than in vacuum. It is suggested that the nodules may reduce the stability temperature of the coatings.

MST/2028     

Anorganische Fasern. Herstellung,Eigenschaften und Verwendung

Inorganic Fibres – Fabrication, Properties and Application Glass- and carbon fibres are preferred reinforcement materials for composites with polymer matrix. Basing on an analysis of their properties it is shown that other inorganic fibres can combine the advantages of both, and avoid their disadvantages. Boron-, siliconcarbide- and alumina-fibres are discussed in detail. The boron fibre has a YOUNG's modulus up to 45 MN/m² and a strength of 3000–4000 MN/m² as well as high compressive and shear strength. Therefore the boron fibres are superior to the carbon fibres as high modulus reinforcement material. The disadvantages of the boron fibres are their complicated fabrication process (chemical vapour deposition on a tungsten monofilament), and their only availability in form of monofilaments with diameters of at least 60 μm. The boron fibre recristallizes at 6000 °C and reacts also with the tungsten substrat. Thus, its application at elevated temperatures is limited. The SiC-fibre shows the same mechanical properties as the boron fibre but it can be fabricated by chemical vapour deposition also on a carbon monofilament. The advantages are the chemical compatibility with carbon substrat and the resistance against oxidation. The disadvantage is the higher density compared with that of boron (3,5 against 2,6 · 10³ kg/m³) Carbon yarns (with 10 000 monofilaments of 10 μm diameter) with SiC coatings of 0,5 μm can be seen as an alternative to the relatively thick SiC-monofilaments with 60 μm diameter. The advantage of such coated carbon yarn is a better applicability in fibre reinforced composite materials. There exists a further alternative preparation process for SiC-yarn, namely the spinning of polycarbosilanes with subsequent formation of SiC by pyrolysis treatment. Al₂O₃-fibres are chemically inert against most oxidic and metallic matrix materials, and promises to be candidate reinforcement materials for aluminium. They can be prepared by melt-spinning process as well as by a hydrolysis-process starting from aluminium organic compounds with subsequent heat treatment for thermal decomposition. The properties of all these fibre materials are compared with those of glass-, polyamid- and carbon-fibres as well as with metal wires.     

Thermal–mechanical modelling of laminates with fire protection coating

This paper presents a modelling approach to analyse the protection provided by passive and intumescent surface coatings on glass fibre reinforced laminate substrates exposed to fire. The modelling involves a multi-stage analytical approach: (i) thermal analysis of heat transfer from the fire through the surface insulation coating, which includes decomposition and expansion in the case of an intumescent material; (ii) thermal–chemical analysis of heat transfer through the fibreglass laminate substrate (beneath the fire protective coating), including decomposition of the polymer matrix; and (iii) thermal–mechanical analysis of softening and failure of the laminate under in-plane tension or compression loading. The modelling approach is validated using experimental temperature and strength data from fire structural tests performed on woven glass–vinyl ester laminates insulated with passive (ceramic fibre mat) or organic intumescent surface coatings.     

Carbon,carbide and silicide coatings

The elements carbon and silicon are the significant constituents of the refractory coating materials discussed in this paper, namely B₄C, pyrocarbon, TiC, SiC, Si₃N₄ and MoSi₂. Because of their hardness and their chemical and oxidation resistance, these materials are of increasing interest as coatings on various substrates. However, their physical and chemical properties limit the number of suitable plating methods. Whilst the CVD technique is the most versatile, the sintering technique is a good alternative, especially if thicker coatings are required.The different coating materials are discussed in detail. The ways in which different coatings can be modified for special applications, e.g. isotropic pyrocarbon coatings for bioengineering purposes, are discussed. Pure silicon carbide and silicon nitride coatings become important as protection against internal oxidation and as barriers in carbon fibre reinforced composites.The problems arising from the simultaneous deposition of two elements to form a specific compound are demonstrated with the examples of SiC, Si₃N₄ and B₄C. The necessity of avoiding chemical reactions with the substrate during deposition is exemplified by the case of TiC coatings on carbon fibres.Finally the technique of preparing metal silicide coatings on refractory metals and carbon by plasma spraying and isostatic hot pressing as protection against oxidation is explained, and the modification of the coatings, in particular to improve thermal cycling behaviour, is discussed.     

Characterisation of thin silica films deposited on carbon fibre by an atmospheric pressure non-equilibrium plasma (APNEP)

Low modulus carbon fibres were used to investigate the potential of a low cost novel atmospheric pressure microwave plasma technique for continuously depositing silica coatings onto carbon fibres, in a tow form. The objective was to improve the interfacial properties of aluminium/carbon fibre composites produced by liquid metal infiltration techniques. Amorphous silica coatings, approximately 50–400 nm thick, were successfully produced in a continuous process. The nature and morphology of the coatings were determined using transmission electron microscopy. Squeeze cast and gas pressure infiltrated samples were manufactured to investigate the fibre/matrix interface using tensile tests and a short beam interlaminar shear test. The tensile samples displayed brittle fracture with ultimate tensile stresses of 223 and 251 MPa for the uncoated and coated fibres, respectively. The shear samples did not show any interlaminar shear, but failed in tension. It is concluded that the silica coating did not have a significant effect on improving the carbon fibre/aluminium matrix interface. However, the microwave plasma technique was very successful and can be modified to produce low cost alternative coatings for future development.     

Interphase modification of alkali-resistant glass fibres and carbon fibres for textile reinforced concrete II: Water adsorption and composite interphases

The interaction between sizings and coatings is varied systematically resulting in different fibre surface modifications and interphase properties in cement matrix composites. The mechanical performance and the water adsorption of sized and coated alkali-resistant glass fibres (ARG) and the working capacity of the composites achieved are elucidated as a function of fibre diameter, sizing and coating content as well as their chemical formulations under special consideration of nanoclay concentrated within the interphase. Depending on the chemistry of the sizing and polymeric coating, respectively, the force–crack width curves together with hydration phase morphology derived from ESEM images of the concrete specimens are used to reveal composite interphases. Furthermore, the results achieved with nanodispersed polymeric coatings on glass fibres are transferred to carbon fibres and their concrete composites.     

Optimization of the interfaces in Nicalon-fibre-reinforced-AIPO-matrix composite materials

The optimization of fibre/matrix interfaces in Nicalon-fibre-reinforced aluminium-phosphatematrix composite materials is addressed. First, the structure and chemical composition of the fibre/matrix interfaces were characterized for the as-fabricated composite materials and for the same materials after high-temperature exposures simulating the conditions of their intended application. Transmission electron microscopy (TEM) showed considerable Si diffusion from the fibres into the matrix accompanied by the formation of an interfacial diffusion/reaction zone in the process of heat treatment at 816 °C and higher temperatures. A BN-fibre coating did not prevent Si diffusion. Next, the interfacial bond strength was measured for the uncoated and some of the coated interfaces. The measurements showed a much lower bond strength in the carbon and carbon/BN coated interfaces than in the uncoated and BN-coated interfaces. Finite-element modelling was used to evaluate the interfacial bond strength which would result in the highest strength of the composite material. This optimal bond strength was found to be characterized by a critical energy-release rate close to 50 J m^–2. Further increase in the interfacial bond strength above 50 Jm^–2 resulted in brittle failure of the composite materials. Finally, the potential fibre coatings which were stable and not reactive with the fibres and the matrix at elevated temperatures were identified for the projected service temperatures of 816 and 1093 °C.     

Plasma-assisted chemical vapour deposition of tin oxide coatings

A feasibility study was performed to assess the potential of plasma-assisted chemical vapour deposition as a method for the coating of carbon fibre bundles. Rayon-based carbon filaments, in 2000-filament tows, were coated with SnO₂. Direct-current and hollow-cathode discharges generated in an SnCl₄-O₂ medium helped to deposit the SnO₂ coatings on fibres that were heated to approximately 800°C, by plasma bombardment, and kept in the plasma for 15 min. Both routes were shown to produce uniform and well adhered coatings, and also to offer advantages in terms of processing temperature and the possibility of continuous processing.