射频直热法在碳纤维表面低温涂覆SiC涂层研究

采用新型工艺射频直热法在碳纤维表面低温化学气相沉积SiC涂层,以达到节能、控制涂层厚度和降低成本的工业生产要求.利用XRD,EPMA,TEM研究了工艺与涂层结构关系、涂层的微观结构、拉伸和抗氧化性能.结果表明:SiC涂层在700～780℃发生结晶,提高温度或者减慢走丝速度,结晶更完善;低温沉积涂覆后纤维的拉伸性能基本不下降,低温抗氧化性能有所提高;样品的高温抗氧化性能并不理想,有待于进一步的工艺探索.     

化学气相沉积法制备SiC/SiO2梯度复合涂层的热力学分析

SiC/SiO2复合涂层是显著改善先进高温气冷用石墨抗氧化性能的一个理想涂层体系,但目前其优化的化学气相沉积工艺还未见诸报道.本研究利用HSC-CHEMISTRY 4.1分析了化学气相沉积工艺对制备的SiC/SiO2复合涂层的影响.分析结果表明:载气中加入足够的氢气对制备不含杂质的SiC/SiO2复合涂层很有必要;合适的沉积温度为1100～1200℃;最佳反应物浓度为:SiCl4摩尔分数为1%～2%,沉积SiC涂层时CH4与SiCl4的摩尔比为1,沉积SiO2涂层时水蒸气与SiCl4摩尔比为2,通过逐渐改变CVD气氛中的水蒸气与CH4的比例来沉积SiC/SiO2梯度过渡层.     

高温化学气相沉积法制备致密碳化钽涂层

采用高温化学气相沉积法(CVD)在高纯高密石墨基片的表面沉积了碳化钽(TaC)涂层。通过研究气化温度、气体流量及沉积温度对TaC涂层表面质量的影响,确定了高温CVD法制备TaC涂层的工艺参数,最终获得高致密度的TaC涂层。     

碳纤维涂覆碳化硅的研究

为了改善碳纤维的抗氧化性能和阻止碳纤维与金属在高温下的化学反应,在碳纤维表面涂覆碳化硅是一种较好的办法。本研究采用化学气相沉积法,在碳纤维表面连续涂覆碳化硅,研究其工艺参数时涂层厚度及涂层成分与结构的影响,得到了该反应体系的表观活化能约为165KJ/mol及碳化硅的结构主要是β型。还着重分析了碳纤维涂覆后强度下降的主要原因,并提出了改进措施。     

渗硅工艺制备ZrB2-SiC涂层的微观结构与抗氧化性能

为了提高陶瓷基复合材料的抗氧化性能,分别采用气相、液相渗硅工艺制备了ZrB₂-SiC涂层,利用静态氧化试验测试了ZrB₂-SiC涂层的抗氧化性能,并分析了涂层的微观结构演化过程。结果表明：气相渗硅工艺制备的涂层抗氧化性能更优良,氧化试验后在涂层表面形成一层致密结构的氧化物层,有效抑制氧化性气体向涂层内部扩散,提高涂层的高温抗氧化防护能力。由于液相渗硅工艺制备的涂层存在残留硅成分和微裂纹,导致涂层高温抗氧化防护能力较差。     

CVD SiC涂层对3D C/SiC氧化行为的影响

采用两种不同沉积速度的等温减压化学气相沉积在3DC／SiC上制备了多层CVD SiC涂层．利用扫描电镜对涂层表面和断面进行显微分析，考察了涂层在1300℃下进行恒温氧化的防护效果．慢速减压化学气相沉积能够对多层CVD SiC涂层的涂层间隙缺陷实现有效控制，所制备的多层涂层可以消除涂层间隙，连贯的结合为一整体，能显著提高涂层防护效果，材料在1300℃空气中氧化30h后的失重率可控制在1％以下。     

化学气相沉积制备MoSi2涂层分析

主要介绍了目前化学气相沉积(CVD)制备MoSi2涂层或薄膜的几种方法,从反应原理和沉积产物结构等方面分析了各种方法的特点,提出了这些方法在制备MoSi2涂层过程中所存在的问题,并讨论了CVD制备MoSi2涂层应用于碳/碳复合材料高温抗氧化保护的可行性.     

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.     

ЭП220涡轮叶片涂层的分析

镍基合金零部件在高温和腐蚀环境中长期使用时,其抗氧化性能及抗热腐蚀性能总是不能满足要求。所以近20年来,较为广泛地采用了涂层防护工艺,以便合金在使用状态下具有良好的表面化学稳定性。本文分析了220涡轮叶片的涂层防护工艺,并对叶片表面层的化学成分及组织结构作了试验测定及分析。     

CVD与炭素

一前言化学气相沉积(CVD)是一种较古老的技术,很早以前,人们就利用CVD技术生产碳黑、碳丝等物质。随着科学技术的进步,CVD本身也得到很大的发展,而且有新的改进,如等离子CVD,激光CVD等。这些新型CVD大大降低了沉积温度,使得CVD技术在材料科学各领域中得到更广泛的应用,同时又发展了性能更优越的新材料品种。在炭素材料领域由于利用CVD技术可使一些传统材料的性能得以改进,如在石墨表面用CVD技术涂覆多种涂层,如PG、SiC     

Deposition of a nanocomposite (Ti,Al, Si)N coating with high thickness by high-speed physical vapor deposition

Nanocomposite coatings such as (Ti, Al, Si)N have been demonstrated as promising candidates for the use as protection against solid particle erosion for compressor blades. Typically, nanocomposite (Ti, Al, Si)N coatings are deposited by different physical vapor deposition (PVD) techniques. However, the relatively low coating thickness up to a few micrometers due to low deposition rates leads to a limited lifetime of the coatings under erosive particle bombardment. In this study, the deposition of a nanocomposite (Ti, Al, Si)N coating was performed by a hollow cathode gas flow sputtering method, the high-speed physical vapor deposition, which enables the high-rate deposition of thick coatings. Morphology and microstructure of the coating were investigated via scanning electron microscopy and transmission electron microscopy, respectively. Tribological characterization by impact tests and erosion tests demonstrates that the nanocomposite (Ti, Al, Si)N coated sample reveals a promising resistance against impact loads and the solid particle erosion. Summarily, nanocomposite (Ti, Al, Si)N coatings deposited by the high-speed physical vapor deposition provide a high potential for the erosion protection of compressor blades.     

Interrupted cutting tests of cemented carbide tools coated by physical vapor deposition and chemical vapor deposition techniques

Refractory compound coatings prolong the life of cemented carbide inserts. The structure of these coatings is vastly different when the same coating is produced by chemical vapor deposition (CVD) and physical vapor deposition (PVD) methods. TiC and HfN coatings were applied to cemented carbide tools by both CVD and PVD processes. The coated inserts were tested under interrupted cutting conditions using slotted bar tests. The CVD-coated inserts failed after a few (less than 100) cycles whereas the PVD-coated inserts lasted well past 2000 cycles without failure as did the uncoated inserts. PVD coatings have a much greater fracture toughness than CVD coatings due to their very fine-grained microstructure with a distribution of fine cavities which act as crack stoppers. In contrast, CVD coatings have a fully dense microstructure with a large grain size which does not have much fracture toughness. Another reason for the difference in behavior is the much lower deposition temperature (about 500°C) used in the PVD process as compared with the much higher deposition temperature (about 1000°C) used in the CVD process. Chemical attack of the cemented carbide substrate occurs at high deposition temperatures, thus weakening the area near the coating-substrate interface.     

CVD法与PCVD法TiN薄膜研究

用等离子增强化学气相沉积（ＰＣＶＤ）法和化学气相沉积（ＣＶＤ）法分别制备ＴiV系薄膜。采用扫描电镜、Ｘ射线衍射仪和连续加载压入仪研究分析薄膜的微观结构、相结构和薄膜的力学性能,并采用电极电位法测定了薄膜的耐腐蚀性能,研究表明,PCVD法ＴiN系薄膜的微观组织形态明显优于同类的ＣＶＤ法薄膜,ＰＣＶＤ法薄膜晶粒尺寸细小,均匀,形态圆整,组织致密;ＣＶＤ法薄膜晶粒形态为多边形,尺寸较粗大、不均匀,组织致密性差,ＰＣＶＤ法ＴiN系薄膜的声望生和结合力等力学性能可达或优于同类ＣＶＤ法薄膜,虽然ＰＣＶＤ法薄膜的氯含量（约为２％）远主ＣＶＤ法薄膜（约为０．５％）,但ＰＣＶＤ法薄膜的耐蚀性能却明显优于ＣＶＤ法薄膜,还研究分析了ＰＣＶＤ法和ＣＶＤ法成膜模式对薄膜微观结构和性能的影响机理。     

Development of CVD Ti-containing films

Ti-containing films have attracted many interests in last decades due to their specific properties, and can be used in many applications. Chemical vapor deposition (CVD) is an advanced manufacture technique for surface coating currently and has been widely used to prepare various surface coatings and thin films. Therefore, researchers have carried out in depth investigations on CVD Ti-containing films in the last decades. This article reviews the development of CVD Ti-containing films in the last years. Ti-containing films can be classified into pure Ti films, binary films, ternary films and quaternary films by components, and are described with extend discussion about their preparaiton, structures, properties and applications. Otherwise, the techniques based on CVD method and the Ti-precursors for Ti-containing films will be presented in the article.     

化学气相沉积SiC涂层生长过程分析

以高纯石墨为沉积基体,MTS为先驱体原料,在负压条件下沉积了CVD SiC涂 层.利用SEM和XRD分别对涂层的形貌及晶体结构进行了表征,SiC涂层表面呈菱柱状, (111)面为择优取向面.利用高分辨透射电镜对涂层与基体的界面结构、涂层的显微结构进行 了研究,得出CVD SiC涂层生长过程如下:SiC最初是沿着石墨基体的晶面取向开始生长 的}随后经历一段取向淘汰及调整的过程后,开始(111)晶面的生长.     

前过渡族元素X对TiAlXN涂层结构与性能的作用EI北大核心CSCD

TiAlN基涂层具有良好的力学和抗氧化性能,因此,在典型的机械部件,如航空发动机压气机叶片、切削刀具和精密模具等表面防护领域得到广泛应用。然而,随着机械部件性能要求的不断提升,涂层的服役条件愈加苛刻,防护涂层的可靠性和服役寿命受到更为严峻的挑战。在TiAlN涂层中添加前过渡族元素以提高涂层的综合性能是有效提高涂层防护效果、延长涂层使用寿命的重点研究方向之一,而元素的选取和成分的确定对涂层的结构优化和性能提升至关重要。本工作从TiAlN涂层材料出发,结合相图详细论述前过渡族元素X(X=V,Cr,Y,Zr,Nb,Mo,Hf,Ta,W)的添加对TiAlN涂层结构和性能的影响,进而探讨TiAlXN涂层的成分-结构-性能关系。针对在TiAlN涂层中添加前过渡族元素面临的缺乏相图计算辅助、四元涂层在极端环境下的失效行为、涂层制备设备成本较高等问题,提出结合相场模拟开发TiAlXN体系四元相图、发展TiAlN基高熵涂层以及结合气相沉积技术的优势大力发展涂层制备技术等展望。     

Properties of Coatings: Comparisons of Electroplated, Physical Vapor Deposited, Chemical Vapor Deposited, and Plasma Sprayed Coatings

Properties of coatings (structure, porosity, density, stress, corrosion, hydrogen permeation, adhesion, tribology, fatigue and thermal contact conductance) produced by a number of deposition methods including electrodeposition, physical vapor deposition, chemical vapor deposition, and flame spraying art; compared. In most cases, the films did not exhibit similar properties. In addition, process conditions often could be varied for any given coating process and this, in turn, would affect microstructure and hence the properties. No coating system provided best results for all these properties. In some cases, electroplated films provided superior results while in others PVD or CVD were best.     

TECHNIQUES FOR COATING MOLYBDENUM

This review covers processes used to deposit adherent coatings on Mo. Coatings applied by electroplating, physical vapor deposition (PVD), chemical vapor deposition (CVD) and plasma spraying are covered. Processing techniques for preparing the substrates for deposition are emphasized and supported with data on adherence of the coatings.     

Chemical vapour deposition of coatings

Chemical Vapour Deposition (CVD) of films and coatings involve the chemical reactions of gaseous reactants on or near the vicinity of a heated substrate surface. This atomistic deposition method can provide highly pure materials with structural control at atomic or nanometer scale level. Moreover, it can produce single layer, multilayer, composite, nanostructured, and functionally graded coating materials with well controlled dimension and unique structure at low processing temperatures. Furthermore, the unique feature of CVD over other deposition techniques such as the non-line-of-sight-deposition capability has allowed the coating of complex shape engineering components and the fabrication of nano-devices, carbon-carbon (C-C) composites, ceramic matrix composite (CMCs), free standing shape components. The versatility of CVD had led to rapid growth and it has become one of the main processing methods for the deposition of thin films and coatings for a wide range of applications, including semiconductors (e.g. Si, Ge, Si_1-xGe_x, III-V, II-VI) for microelectronics, optoelectronics, energy conversion devices; dielectrics (e.g. SiO₂, AlN, Si₃N₄) for microelectronics; refractory ceramic materials (e.g. SiC, TiN, TiB₂, Al₂O₃, BN, MoSi₂, ZrO₂) used for hard coatings, protection against corrosion, oxidation or as diffusion barriers; metallic films (e.g. W, Mo, Al, Au, Cu, Pt) for microelectronics and for protective coatings; fibre production (e.g. B and SiC monofilament fibres) and fibre coating. This contribution aims to provide a brief overview of CVD of films and coatings. The fundamental aspects of CVD including process principle, deposition mechanism, reaction chemistry, thermodynamics, kinetics and transport phenomena will be presented. In addition, the practical aspects of CVD such as the CVD system and apparatus used, CVD process parameters, process control techniques, range of films synthesized, characterisation and co-relationships of structures and properties will be presented. The advantages and limitations of CVD will be discussed, and its applications will be briefly reviewed. The article will also review the development of CVD technologies based on different heating methods, and the type of precursor used which has led to different variants of CVD methods including thermally activated CVD, plasma enhanced CVD, photo-assisted CVD, atomic layer epitaxy process, metalorganic assisted CVD. There are also variants such as fluidised-bed CVD developed for coating powders; electrochemical vapour deposition for depositing dense films onto porous substrates; chemical vapour infiltration for the fabrication of C-C composites and CMCs through the deposition and densification of ceramic layers onto porous fibre preforms. The emerging cost-effective CVD-based techniques such as electrostatic-aerosol assisted CVD and flame assisted CVD will be highlighted. The scientific and technological significance of these different variants of CVD will be discussed and compared with other vapour processing techniques such as Physical Vapour Deposition.     

Study of the delamination of diamond coatings under thermal stress

The influence of the thickness of CVD diamond coatings on the adhesion to a substrate, after cooling down from deposition temperature to room temperature, has been studied experimentally and theoretically. Diamond layers have been deposited at 850°C on W substrates by microwave plasma enhanced CVD. Cooling down of the substrate-diamond coating system to room temperature induces thermal stresses, due to different thermal expansion coefficients of coating and substrate. For thick diamond coatings a total and sudden delamination could be observed as a consequence of these stresses. On the contrary thin coatings, produced under identical circumstances, adhered well. These phenomena have been modelled and explained by the use of an energetic criterion for the delamination of a two-layer system under thermal stress. From the model a critical thickness of the coating can be calculated. Above this critical thickness, delamination will suddenly occur. The calculations also predict that for intermediate coating thicknesses delamination can easily be induced by external causes.