功能金属/陶瓷梯度热障涂层的材料体系及制备方法

介绍了功能金属/陶瓷梯度热障涂层各组成层材料的选择,以及梯度过渡层的设计原则和方法,讨论了制备梯度热障涂层常用的方法。最后展望了过渡层设计方法的发展方向,提出了制备功能金属/陶瓷梯度热障涂层方法的选择原则。     

功能梯度表面涂层热锻模的仿真设计与分析

针对热锻模损伤主要发生在模具表面的情况,构想使用梯度功能材料对均质材料制造的热锻模进行表面处理,阐述了梯度材料锻模表面涂层的设计方法,建立了基于Deform软件的热锻成形有限元模型,分析对比了均质热锻模与梯度材料表面涂层热锻模在锻造生产后的温度场和应力场,从而论证了在热锻模表面进行梯度材料表面复合涂层处理的优越性。     

EB-PVD制备SOFC电解质涂层的显微结构表征

采用大功率EB-PVD工艺在NiO-YSZ多孔基体上制备了20 μm厚的YSZ电解质涂层材料.SEM分析表明制备态涂层表面由1 μm～10 μm的晶粒组成并含有少量微米级的孔隙,涂层材料的断面SEM表明涂层致密并和基体结合良好.EPMA分析显示初始蒸发阶段制备的涂层材料内Y,O元素分布均匀,Zr元素的分布存在一个梯度.XRD分析表明:涂层为典型的立方相结构并表现出择优取向特征.     

EB-PVD制备SOFC电解质涂层的显微结构表征

采用大功率EB-PVD工艺在NiO-YSZ多孔基体上制备了20μm厚的YSZ电解质涂层材料。SEM分析表明制备态涂层表面由1μm～10μm的晶粒组成并含有少量微米级的孔隙，涂层材料的断面SEM表明涂层致密并和基体结合良好。EPMA分析显示初始蒸发阶段制备的涂层材料内Y，O元素分布均匀，Zr元素的分布存在一个梯度。XRD分析表明：涂层为典型的立方相结构并表现出择优取向特征。     

等离子喷涂Sm2Zr2O7/NiCoCrAlY功能梯度热障涂层的热冲击性能

采用有限元法计算了涂层结构、材料成分等对等离子喷涂Sm2Zr2O7/NiCoCrAlY功能梯度热障涂层热冲击性能的影响。结果表明:径向热应力在试样边沿急剧降低,而轴向热应力在边沿处发生从压应力向拉应力的突变;从基体至涂层表面,涂层中的径向冲击热应力逐渐增大,增加涂层层数可缓解热应力;材料组成对涂层的冲击热应力影响不明显。所研究的1357功能梯度热障涂层具有最好的抗热冲击性能。     

Mo-MoSi_2功能梯度材料的三点弯曲行为

采用渗硅工艺制备了Mo-MoSi2功能梯度材料,并利用扫描电镜、X射线衍射以及弯曲强度试验观察并分析Mo-MoSi2功能梯度材料的微观结构和断裂行为。结果表明,梯度材料由表及里的结构变化形式为表层MoSi2晶粒(尺寸为6.8μm)+少量Si→MoSi2柱状晶粒(长度为15μm)→过渡层(2μm)→Mo基体。该Mo-MoSi2功能梯度材料具有组织致密,MoSi2晶粒细小,梯度层与Mo基体界面结合良好等特点。Mo-MoSi2梯度材料具有良好的弯曲性能,弯曲强度为1025 MPa,断裂挠度为1.87 mm,弹性模量为26.6 GPa。在保证Mo基体强度的同时,MoSi2功能梯度涂层显著提高了Mo基体塑性性能。Mo-MoSi2梯度材料的弯曲断裂形式主要为沿晶断裂和穿晶断裂两种形式。过渡层和MoSi2涂层形成是Mo-MoSi2功能梯度材料断裂韧性提高的主要原因。     

Al/SiC功能梯度材料(FGM)涂层板的安定性分析

目的对热机械载荷环境下的金属/陶瓷功能梯度材料涂层板进行安定性分析,并获得其安定载荷区域,为其工程安全使用提供一定的理论依据。方法在已有工作基础上,采用分段指数函数模型描述梯度涂层板中的材料热物参数空间梯度分布,基于静力安定理论建立梯度涂层板弹性区域的理论分析模型和安定区域的理论分析模型,通过编程数值计算,结合自平衡的残余应力场和板内应力分布情况,分析了Al/SiC功能梯度材料涂层板的安定区域。结果计算分析出Al/SiC功能梯度材料涂层板弹性区域边界和安定区域边界,其中安定区域边界由两部分组成,一部分为Shakedown-Reversed Plasticity boundary(S-RP),另一部分为Shakedown-IncrementalCollapseboundary(S-IC),并得到处于安定情况下所能承受的极限热载增量为(35)q=154 4.0℃,单位厚度下所能承受的极限机械载荷为=6167.3 N/mmxP。涂层板上表面热物理性能最弱,最容易发生塑性循环变形破坏。结论根据安定分析结果,可预先选择功能梯度涂层板所能使用的热机械环境,为涂层板的安全使用提供可靠的理论依据。另外,为得到更佳的安定区域和适应更苛刻的热机械环境,安定分析结果可对涂层板制备优化设计提供较好的参考。     

火焰喷涂梯度功能陶瓷涂层工艺与性能

用氧乙炔火焰喷涂法制备铜基氧化铝陶瓷梯度功能涂层,对比了无梯度涂层、梯度涂层及台添加剂梯度涂层的性能,结果表明,梯度功能涂层性能明显优于普通涂层,其中加入5％Al呈线性分布的11层梯度功能涂层的综合性能（抗热震性、隔热性、结合强度、硬度梯度）最佳。     

反应电火花沉积合成TiC/Ti复合涂层研究

利用DZ-1400型电火花沉积/堆焊机,以高纯石墨为电极,在TC4钛合金基体表面制备了厚度为70～110 μm的TiC增强金属Ti基复合涂层.利用SEM、XRD、EDS、AES和XPS等检测手段分析了涂层的形貌、组织、物相和化学组成,利用显微硬度计测试了涂层截面显微硬度.结果表明:涂层主要由TiC、Ti和C相组成,TiC是电极材料与基体材料反应形成的新相,是涂层的主要组成相;涂层组织致密、均匀、连续,涂层与基体形成良好的冶金结合;涂层硬度呈梯度变化,随着距表面距离的增大而减小,涂层最大硬度是基体的5.7倍.     

膜基-体化耐高温蒙皮材料的制备及抗热震性能研究

采用电子束物理气相沉积技术(Electron Beam Physical Vapor Disposition, EB-PVD)通过连续蒸镀成功制备陶瓷ZrO_2涂层和以镍基合金为基体的一体化薄板材料.结果表明,ZrO_2涂层致密,具有柱状晶组织,无明显的织构存在.涂层与基体材料间有明显的成分连续梯度变化区域.抗热震性能测试结果显示,一体化材料的ZrO_2梯度涂层能明显延缓热震裂纹的形成和扩展,具有良好的抗热震性能.     

梯度功能材料研究的一些进展

综述了近年来梯度功能材料(FGM)在优化设计、制备、性能评价以及应用方面的最新研究进展，并对其中的热点问题作了系统阐述。对于热应力缓和型FGM，其优化设计的关键环节是准确分析残余热应力的大小和分布。液相法制备FGM以其低成本、操作简单的优势将会获得更大的发展。对FGM的性能测试要尽可能模拟实际使用环境下载荷的不均匀分布。梯度功能热障涂层是FGM的重要应用之一，它与传统的热障涂层相比可明显提高耐久性。此外，还介绍了FGM在面向等离子体护墙材料以及生物材料上的应用。     

Present status of research on design and processing of functionally graded materials

Recent activities in the research of functionally graded materials (FGMs) are reviewed with an emphasis on the fabrication techniques for graded microstructure and functions. The research activities have focused on the processing of graded structures that satisfy the designed functions. Several examples of practical applications of FGMs are described in the present paper to demonstrate the fabrication approaches typical to this kind of material. The remainder of the paper is devoted to summarizing a recently finished national project supported by the Ministry of Education of Japan. Research and developments with respect to FGMs in various fields including physics, chemistry, medical science, and biology are briefly reviewed. This article is based on a presentation made in the symposium “The 3rd KIM-JIM Joint Symposium on Advanced Powder Materials”, held at Korea University, Seoul, Korea, October 26–27, 2001 under auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals. Present at the Fine Ceramic Center, Atsuta-ku, Nagoya, Japan     

Inspection of compositionally graded mullite coatings using laser based ultrasonics

Functionally graded materials (FGMs) have spatial variations in composition and structure resulting in corresponding changes in material properties. These materials can be developed for applications in which the functional requirements of a component are position dependent. In this paper, we evaluate the feasibility of using a laser based ultrasonic technique to determine the distribution of elastic properties in FGMs. A model for the laser generation of ultrasound in a compositionally graded coating on a semi-infinite substrate is used to explore the relationship between the acoustic wave propagation and depth dependent elastic property profile. Surface acoustic waves (SAW) generated in such a system are dispersive, and the dispersion characteristics are highly dependent on the mechanical property profile. A high-resolution laser ultrasonic system has been developed, and experimental measurements of the mechanical properties of single layer mullite coatings are presented. Using compositionally graded mullite coatings as a model system, numerical results are reported showing the sensitivity of SAW dispersion behavior to various composition profiles.     

Microstructures and wear resistances of hybrid Al–(Al3Ti+Al3Ni) FGMs fabricated by a centrifugal method

The Al based functionally graded materials (FGMs), reinforced by a hybrid of Al₃Ti platelets and Al₃Ni granular particles, were fabricated by the centrifugal method with both ingots of commercial Al–5mass%Ti and Al–20mass%Ni master alloys. The ratios of Al–Ti and Al–Ni alloys were 3:1, 1:1 and 1:3 (in mass), and the applied G numbers are 30, 50 and 80. The microstructures of hybrid Al–(Al₃Ti+Al₃Ni) FGMs were observed with an optical microscope (OM) and a scanning electron microscope (SEM). Since the gradient distributions in orientation of Al₃Ti platelets and in particle size of Al₃Ni primary crystal particle were expected to be formed in the fabricated hybrid Al–(Al₃Ti+Al₃Ni) FGMs, detail observations of the orientation of Al₃Ti platelets and the size of Al₃Ni granular particles were performed. The wear resistance of the FGMs was measured by an Okoshi-type wear machine. Based on the experimental results, the advantages of hybrid Al–(Al₃Ti+Al₃Ni) FGMs were discussed.     

Corrosion behaviour of Al/Al3Ti and Al/Al3Zr functionally graded materials produced by centrifugal solid-particle method: Influence of the intermetallics volume fraction

Intermetallic particles, Al₃Ti and Al₃Zr were formed in Al–5mass%Ti and Al–5mass%Zr alloys, respectively, by centrifugal casting, in order to create functionally graded materials (FGMs). At present, no information is available on the influence of the amount of intermetallics on the electrochemical properties of these alloys.In this paper, the corrosion resistance of Al/Al₃Ti and Al/Al₃Zr FGMs was investigated by open-circuit measurements, potentiodynamic polarization and electrochemical impedance spectroscopy. Results suggests that the corrosion resistance of the FGMs is affected by galvanic effects between the intermetallic particles and the metallic matrix. Lower centrifugal forces resulted in an improvement of the electrochemical properties.     

Functionally gradient (YSZ-20% Al<Subscript>2</Subscript>O<Subscript>3</Subscript>)−SUS422 composites

Functionally gradient materials (FGMs) were prepared by mixing 5 layers comprised of different ratios of (YSZ-20%Al₂O₃) and 422 stainless (SUS422) powders, followed by hot pressing for densification. Two design concepts were proposed: One as a FGM with a monotonic change of the CTE (coefficient of thermal expansion) for each layer, and is designated as the monotonic mode, and the other was a FGM with a change of CTE that is not monotonic for each layer, and is termed the non-monotonic mode. The FGM with a monotonic CTE mode cracked at the ceramic surface after it was removed from the hot pressing furnace. In contrast, the FGM with a non-monotonic CTE mode survived after hot pressing. Based on ABAQUS simulation results, a non-monotonic change in CTE resulted in a decrease of residual stress on the ceramic side but an increase inside the metal-rich layers of the FGMs. The induced change in the stress distribution inside the FGMs was compromised by the deformation of the metal-rich ingredient (SUS422) in the FGM. Thermal shock tests of FGMs were performed between 25°C and 600°C. The non-monotonic FGM endured up to 100 thermal cycles with only slight bending, and was free of delamination and cracking. The use of composition-adjusted layers to manipulate thermal expansion coefficients of each layer greatly changed the stress contour of the FGM. It is noted that a modified functional-gradient FGM can be fabricated with a hard ceramic surface on one side to resist high temperature, and a ductile metallic surface on the other side to provide toughness.     

电场激活原位合成(TiC)pNi/TiAl/Ti功能梯度材料

运用电场激活压力辅助合成(FAPAS)和原位合成技术制备了(TiC)pNi/TiAl/Ti功能梯度材料,研究了电场对材料合成及层界面扩散连接的作用。采用光学显微镜、扫描电子显微镜、能谱和X射线衍射仪分析了梯度材料各层及界面微观组织、相组成和元素分布。结果表明,电场的施加以及TiAl的燃烧反应是合成材料的关键;经原位合成的TiC颗粒均匀细小;金属陶瓷层/TiAl/Ti基板的界面区产生了成分的互扩散并形成了良好的冶金结合。钛板到金属陶瓷层的显微硬度呈梯度变化且具有较好的抗热震性。     

Determination of properties of graded materials by inverse analysis and instrumented indentation

In this paper, a new measurement procedure based on inverse analysis and instrumented micro-indentation is introduced. The inverse analysis is utilized to extract information from indented load–displacement data beyond usual parameters such as elastic modulus. For the initial implementation of this procedure, determination of non-linear functionally graded materials (FGMs) parameters is considered. In FGMs, the compositional profile and the effective mechanical property through the thickness are essential in verifying the fabrication process and estimating residual stresses and failure strengths. However, due to spatial variation of their properties, it is often difficult or costly to make direct measurements of these parameters. In order to alleviate the difficulties associated with testing of FGMs, we propose an effective but simple procedure based on the inverse analysis which relies solely on instrumented micro-indentation records. More specifically, the Kalman filter technique, which was originally introduced for signal/digital filter processing, is used to estimate FGM through-thickness compositional variation and a rule-of-mixtures parameter that defines effective properties of FGMs. Essentially, the inverse analysis processes the indented displacement record at several load magnitudes and attempts to make best estimates of the unknown parameters. Our feasibility study shows promising results when combined data from two differently sized indenters are employed. The procedure proposed is also applicable in estimating other physical and mechanical properties of any coating/layered materials.     

Microstructures of functionally graded materials fabricated by centrifugal solid-particle andin-situ methods

Functionally graded materials (FGMs) belong to a relatively new class of inhomogeneous composite materials, in which the composition and/or microstructure undergo a gradual change along some directions. In this review article, the microstructures and composition gradients in Al/SiC, Al/Shirasu (volcanic eruptions commonly found in south Kyushu in Japan), Al/Al₃Ti, Al/Al₃Ni, Al/Al₂Cu FGMs have been investigated. The Al/SiC, Al/Shirasu and Al/Al₃Ti FGMs are fabricated by the centrifugal solid particle method where the distribution particles of SiC, Shirasu and Al₃Ti are solids in the melts. On the other hand, Al/Al₃Ni and Al/Al₂Cu FGMs are fabricated by the centrifugalin-situ method where Al/Al₃Ni and Al/Al₂Cu systems have lower liquidus temperatures than the processing temperatures. The feature of Al/(Al₃Ti−Al₃Ni) hydrid FGM, which is fabricated by a method combining both the centrifugal solid-particle andin-situ methods, is also shown.     

Wear of Al/Al3Zr functionally graded materials fabricated by centrifugal solid-particle method

In this study, Al–5mass%Zr functionally graded materials (FGMs) were fabricated by the centrifugal solid-particle method (CSPM) under applied centrifugal force of 30, 60 and 120G (units of gravity). Microstructural observation along the centrifugal force direction showed that Al₃Zr platelet particles are almost oriented normal to the applied centrifugal force direction. Volume fraction of Al₃Zr particles increases close to the ring surface. Moreover, this distribution range of Al₃Zr particles becomes broader with decreasing the applied centrifugal force. The wear anisotropy of the fabricated Al/Al₃Zr FGMs was strongly influenced by the platelet particles orientation at the test position. Investigating both of the worn surface morphology and the sub-worn surface layer showed that plastic deformation induced wear is the dominant mechanism during the wear process of Al/Al₃Zr FGMs samples. Therefore, some of the tested samples were severely deformed and an Al₃Zr particles-free layer containing Al–Zr supersaturated solid solution was observed very near to the worn surface during the wear test.