Ti-Si共晶钎料的制备及其对SiC陶瓷可焊性

采用海绵钛和单晶硅为原料,通过非自耗电弧熔融技术制备91.5Ti-8.5Si(wt%)和22Ti-78Si(wt%)共晶钎料.在真空中1400℃×10min条件下,研究了共晶钎料对SiC陶瓷的润湿性能和界面反应.结果表明:两种共晶钎料对SiC陶瓷均具有良好的润湿性能,润湿角分别约为10°和25°.在润湿实验后,91.5Ti-8.5Si(wt%)钎料和SiC陶瓷分离,22Ti-78Si (wt%)钎料和SiC陶瓷之间结合紧密.在润湿实验的温度制度下,用22Ti-78Si (wt%)钎料(厚度为0.2mm)对SiC陶瓷进行了初步连接,接头的抗弯强度为72MPa.采用SEM、EDS、XRD等检测手段对钎料的形貌和物相组成、钎料和SiC陶瓷的界面结合情况进行了表征,揭示了钎料对SiC陶瓷润湿性和界面反应的机理.     

Ni基高温钎料对Cf/SiC陶瓷基复合材料的润湿性研究

研究了温度和活性元素Cr对Ni基高温钎料在3D-Cf/SiC陶瓷基复合材料上润湿的影响.采用扫描电镜与能谱仪检查界面微观结构与元素分布,通过X射线衍射仪检测界面产物.实验结果表明:升高温度,Ni基钎料在Cf/SiC上的润湿角减小;并且随钎料中的Cr的质量分数增加,润湿角减小.润湿过程属于反应润湿,润湿界面生成多种碳化物和硅化物.     

ZrO2陶瓷与镍活性钎焊界面反应机理研究

本文研究了活性钎焊法连接ZrO2陶瓷和金属镍的界面反应机理,采用微观组织观察、力学性能测试等方法,确定钎焊接头元素分布及反应生成物,从而研究活性钎焊界面反应机理。实验采用rri活性剂,发现活性钎焊法钎焊ZrO2陶瓷和金属Ni,钎料两侧界面出现比较明显的化学反应层和物理润湿层。反应层为活性元素n的主要集中区域,由于受到了zr元素扩散的影响,Ti在陶瓷表面富集现象减弱,cu与Ti的共存现象说明其也是反应的参与元素,她主要集中在焊缝中部。物理润湿层主要是cu、Ni形成的固溶体,还夹杂有少量金属氧化物。x射线衍射分析结果显示反应层界面的主要产物包括cu、Ti和．Ti、船金属间化合物,Ti的氧化物和cu-Ti-0、Ni-Ti-0化合物。通过力学性能测试,在1060℃时接头剪切强度得到提高,达到124Mpa。     

活性钎料Cu_(50)Ti_(50)在Sialon陶瓷表面的润湿动力学观察

采用躺滴技术观察了在1248K 活性钎料 Cu_(50)Ti_(50)在 Sialon 陶瓷表面的铺展动力学过程,并用 X射线衍射技术鉴定了在金属/陶瓷界面上产生的界面反应产物。结果发现,在试验条件下(1248K,0—5min),这种活性钎料在陶瓷表面流动时,润湿半径与铺展时间的平方根之间存在很好的线性关系。就作者所知,这一规律是第一次在金属—陶瓷系统中被发现和报道,其机理有待于进一步研究。     

Ag-Cu钎料与双相陶瓷透氧膜的润湿和界面反应研究

用座滴法测试Ag-Cu合金钎料对Ce_0.8Gd_0.2O_2-δ-NdBaCo₂O_5+δ(CGO-NBCO)双相透氧膜的润湿性, 利用SEM-EDS分析润湿和界面反应机理。结果表明: 空气条件下Ag-Cu合金与CGO-NBCO间的润湿遵从界面反应润湿机制。随着Cu含量的增加, Ag-Cu合金对透氧膜润湿性能提高, Cu含量为6.6mol%~15.8mol%时, 润湿角在35°~20°左右。在润湿界面处出现Cu氧化物的富集, 并且在透氧膜侧生成一层由Cu氧化物和CGO-NBCO双相透氧膜反应产生的Ba-Cu-O、Co-Cu-O和Nd-Ce-Cu-O等复杂氧化物相构成的产物层, 新的界面反应层的生成有利于Ag基合金钎料的润湿, 改善了钎料的润湿性能。     

氧化铝陶瓷与低碳钢钎焊接头的界面反应

采用真空保护下的活性金属钎焊法对95%(质量分数)氧化铝陶瓷与低碳钢进行了钎焊,所用钎料为Ag-Cu-Ti3活性钎料.通过X射线衍射仪(XRD)对界面的反应产物进行了物相分析,并用能谱仪(EDAX)分析了界面元素组成.结果表明,钎焊接头界面的反应十分复杂,反应产物多种多样,主要是Ti3Cu3O,Ti3A1,TiMn,TiFe2,TiC等物质,界面的反应层按A12O3陶瓷/Ti3Cu3O/Ti3Al TiMn TiFe2 Ag(s,s) Cu(s,s)/TiC/低碳钢的规律过渡.     

Ag-Cu钎焊透氧膜不锈钢支撑体侧的界面润湿及反应机理

研究了空气气氛下不同Cu含量的Ag-Cu钎料与不锈钢支撑体的润湿和界面反应机理。采用座滴法研究了界面润湿变化规律,利用SEM观察了连接界面的形貌结构,并结合EDS对界面反应产物组成进行分析。结果表明,纯银与310S不锈钢不润湿;随着钎料中Cu含量的增加,钎料与不锈钢的润湿角显著减小,润湿性能明显改善;当Cu含量增加到2%(质量分数)之后,润湿角减小的趋势变缓。钎料中的CuO与不锈钢表面反应生成Cu-Cr-Fe-O复杂氧化物使基体表面的Cr氧化物膜破坏,改善了钎料与不锈钢的润湿性能。     

Ag-CuO钎料与BaCo0.7Fe0.2Nb0.1O3-δ透氧膜陶瓷润湿及界面反应机理的研究

利用座滴法润湿实验,借助SEM和EDS测试,研究了Ag-CuO钎料与BaCo0.7Fe0.2Nb0.1O3-δ透氧膜陶瓷润湿及界面反应机理。结果表明Ag-Cu-O/BCFNO间的润湿遵从界面反应润湿机制,随Cu含量增加和温度升高,润湿角快速减小。当Cu含量为3.3%(摩尔分数)时,在界面处BCFNO侧开始生成1层反应层,反应层的存在降低了固液界面能,使界面润湿性得到改善,相互冶金作用增强。反应层产生的原因是界面处发生了界面反应CuOx+BaCoFeNbO→Ba-Cu-O+Co-Cu-O,生成的复杂氧化物Ba-Cu-O、Co-Cu-O在BCFNO基体的晶粒边界上呈岛状分布。     

几种高温钎料对C/C复合材料的润湿性研究

采用座滴法测试了10种钎料对C/C母材的润湿性.实验结果表明:随着活性元素Ti,Cr,V含量的提高,钎料润湿性逐渐改善.在Co-Ti和Ni-Ti钎料体系中,Ti元素的存在形式对钎料润湿性影响很大,Ti以固溶体形式存在,易于向C/C母材偏聚发生反应,从而提高润湿性,且润湿界面附近的Ti和C主要以TiC形式存在.采用PdNi-Cr-V-Si-B钎料的润湿界面中,活性元素Cr和V存在于扩散反应层中,推断Cr主要以Cr23C6形式存在,而V以V2C形式存在.当Cr和V同时加入钎料中,Cr向界面反应层扩散的倾向更明显.     

SiC陶瓷真空钎焊接头的组织及性能分析

采用BNi-5钎料对SiC陶瓷进行真空钎焊, 获得了力学性能良好的SiC钎焊接头, 并对焊缝的微观结构和形成过程进行了分析。研究结果表明, Ni基钎料与SiC母材发生反应生成层状界面反应层结构, 所形成的SiC钎焊接头钎缝微观形貌可以表述为:SiC母材/石墨+Ni₂Si/Ni₂Si/石墨+Ni₂Si/Cr₃Ni₂SiC/Ni+Cr₃Ni₅Si₂/Cr₃Ni₂SiC/石墨+Ni₂Si/Ni₂Si/石墨+Ni₂Si/SiC母材。所得SiC钎焊接头常温力学性能较好, 平均钎焊接头剪切强度可达到124 MPa。Ni基钎料钎焊SiC陶瓷接头的断裂位置位于钎料与陶瓷基体间的界面反应层, 主要原因是界面反应层中Ni₂Si和Cr₃Ni₂SiC等脆性化合物在钎焊接头拉伸变形过程中会产生应力集中, 在残余钎焊应力的共同作用下钎焊接头发生断裂。     

Brazing Al2O3 to sintered Fe-Ni-Co alloys

Active metal brazing has been widely used to join ceramics to metals, as sound joints are usually achieved in a single step process without special equipment. However, residual stresses may be a potential problem especially upon joining ceramics to alloys with relatively high thermal expansion coefficients. This work investigates the brazing behavior of Alumina (Al₂O₃) to a sintered Fe-Ni-Co alloy, specially designed to match its coefficient of thermal expansion to that of the ceramic counterpart. The results indicate the presence of an interfacial zone whose microstructure depends on the filler alloy employed. A relationship was established between the microstructure of the interface and the flexural strength of the joints.     

Interface Interactions of Dissimilar Materials at Elevated Temperatures

This paper reviews some of the chemical interactions that occurred at the interface of ceramic/molten metal liquids. Control of interfacial reactions between dissimilar materials is an important issue in numerous technological applications, such as brazing of ceramics to metals, design of ceramic–metal composites, coatings of ceramics on metal substrates, and development of crucibles for melting of refractory metals. In ceramic/metal systems, wetting of the ceramic surface by the liquid metal is typically accompanied to some extent by interfacial reactions. The chemical incompatibility between the metal and non‐metallic materials can result in the formation of undesirable phases, due to the chemical and metallurgical reactions that take place during processing or in service. There is a need, therefore, to characterize the governing factors and reaction pathways at these interfaces. So, when the reaction products obtained during interdiffusion processing are not favorable, the diffusion pathway can be modified to control their formation.     

REVIEW OF SOME PROCESSES FOR CERAMIC-TO-METAL JOINING

Various methods are discussed for the joining of ceramics to metals and vice versa. State-of-the-art techniques including refractory metallizations and active metal brazing are detailed from both a processing and applications standpoint. Various approaches to forming ceramic/metal joints or thin film coatings have been developed over the years to address the need to combine the properties of both types of materials for both electrical and structural applications. These methods address not only physical and chemical compatibility concerns but also the need for bonds between dissimilar materials to survive the rigors of use generated by such inevitable mismatches as can be found in expansion, elastic, reactive and thermal cycling behavior.     

Advances in brazing of ceramics

The main parameters in direct brazing of ceramics to ceramics and to metals are reviewed, with primary emphasis on those influencing wetting of solid ceramics by liquid filler metals. In general, wetting of ceramics by conventional brazing alloys has been regarded as difficult. As a consequence, premetallization of the faying surfaces is frequently used to facilitate the brazing of ceramics. However, it is evident from the literature that recent developments in filler metals, based on active metal (e.g. Ti) additions (the amount depending on alloy composition and type of ceramic), have provided a basis for a substantial reduction of the contact angle. This favourable effect is caused by their reactivity, resulting in the formation of oxides when joining oxide ceramics (e.g. Al₂O₃), and nitrides or carbides and suicides in the case of nonoxide ceramics (e.g. Si₃N₄ or SiC). In addition to insufficient wetting, the mismatch in thermal expansion between the joint members may give rise to a low strength level due to the formation of high residual stresses on cooling. These stresses may limit the maximum allowable flaw size in ceramics to a few micrometres, i.e. of a similar size to that of pores.     

The effect of interlayer metals on the strength of alumina ceramic and 1Cr18Ni9Ti stainless steel bonding

The effects of interlayers of molybdenum and copper on the strength of alumina ceramic and 1Cr18Ni9Ti stainless steel bonding with Ag₅₇Cu₃₈Ti₅ filler metal were investigated. The interfacial morphologies were observed and analysed by scanning electron microscopy and energy dispersive X-ray (EDX) analysis, respectively. The joint strength was examined by shear tests. When using a molybdenum interlayer, the joint strength could be greatly improved because molybdenum not only reduced the interfacial residual stress, but also did not affect the interfacial reaction between the ceramic and the filler metal, and the maximum value was obtained when it was about 0.1 mm thick. When using copper as an interlayer, the joint strength was not increased but decreased, because copper reduced the activity of titanium in the filler metal, resulting in an insufficient interfacial reaction between the ceramic and the filler metal and the formation of poor interfacial adhesion. Therefore, in selecting an interlayer metal to reduce or avoid interfacial residual stress in joining ceramics to metals, in which the interfacial reaction of ceramic and filler metal is important to the joints, the interaction of interlayer metal and filler metal must be considered.     

中间层辅助钎焊陶瓷与金属缓解残余应力研究进展

当陶瓷与金属进行钎焊连接时,由于两种材料热膨胀系数差异较大,接头中易产生较大残余应力,降低接头强度。引入中间层缓解接头残余应力是最简单高效的方法之一。本研究主要从提高焊缝塑韧性和接头形成良好热膨胀系数梯度过渡两方面来分析引入中间层辅助钎焊缓解残余应力的特点。综述了Cu箔软性中间层、三维SiO₂纤维增强复合材料中间层(3D-SiO₂-fiber)、泡沫金属中间层(泡沫Cu、泡沫Ni和泡沫不锈钢)以及多孔SiC陶瓷缓解接头残余应力的研究现状,重点介绍了采用以上中间层辅助钎焊后,接头微观组织的优化对接头力学性能的影响,最后对中间层辅助陶瓷与金属钎焊连接的发展趋势进行展望,以期为未来陶瓷与金属连接技术的突破提供参考。     

陶瓷与金属活性钎焊的研究进展

活性金属钎焊是陶瓷／金属（陶瓷／陶瓷）接合的一种重要方法。本文综述了近年来活性钎焊及其界面行为研究的现状和进展。有关活性钎焊虽已开展了广泛的研究，但尚有许多基本问题需要深入解决。     

陶瓷空气反应钎焊研究综述

高温电化学装置技术优势明显,市场潜力巨大,其特殊的服役环境对钎焊接头提出了更高要求,空气反应钎焊连接方法应运而生。综述了目前常用于RAB连接的钎料种类和已成功实现RAB连接的陶瓷/金属体系,并对相关接头界面组织和综合性能进行了分析。迄今为止,Ag-Cu O钎料使用最广。利用空气反应钎焊方法能够成功实现氧化物、钙钛矿陶瓷自身及其与部分耐高温不锈钢的可靠连接,结合界面成形良好,接头性能稳定。常用于RAB连接的氧化物陶瓷以YSZ和Al_2O_3为代表,LSCF/BSCF/BCFN/BCFZ等典型钙钛矿陶瓷也可利用RAB进行连接。Crofer22 APU,AISI310S和AISI314等耐高温不锈钢与上述钙钛矿陶瓷进行RAB连接后,接头的力学性能、抗氧化能力和气密性均能满足使用需求。在此基础上,对空气反应钎焊的连接特性与研究现状进行了总结。最后,对其发展前景和未来研究方向进行了展望。     

Strength estimation of ceramic–metal joints with various interlayer thickness

ABSTRACT Residual stresses generated by the mismatch of thermal expansion coefficients of ceramics and metals affect the strength of ceramic–metal joints. An interlayer metal can be inserted between the ceramic and metal in order to relax this stress. An analysis was carried out of the residual stresses produced during joint‐cooling and in 4‐point bending tests. The effects of interlayer thickness on ceramic–metal joint strength were then studied by considering a superimposed stress distribution of the residual stress and the bending stress. Finally, joint strength was estimated from fracture mechanics and strength probability analysis by considering the residual stress distribution, defect size and position of pre‐existing defects in the ceramic parts. As a result of this study, we suggest an optimum material selection and interlayer thickness for ceramic–metal joint structures. This approach is generally suitable for the design of electrical and mechanical structures.     

A wettability study of Cu/Sn/Ti active braze alloys on alumina

Active brazing is one of the ideal ways to make metal/ceramic joints. The active braze alloy contains active element(s), such as: Ti, Zr, Cr... etc., reacting and wetting the ceramic surfaces during brazing. Therefore, a strong chemical bonding can be formed after brazing. Cu base active braze alloys are alternatives among active braze alloys. With the aid of additional melting point depressant, Sn, in Cu-Ti alloys, the intermetallic phase in the active braze can be changed. However, its ability to braze structural ceramics, e.g. alumina, needs further study. The purpose of this research is concentrated on the wettability study of the Cu/Sn/Ti alloy on polycrystalline alumina. Based on the experimental results, the minimum Ti content is 6 wt pct in order to effectively wet alumina. Volume fraction of the intermetallic phase in the braze will be greatly increased if the Ti content in the alloy is increased to 12 wt pct. According to sessile drop test results, 70Cu-21Sn-9Ti demonstrates the best wetting ability on alumina. Meanwhile, the Sn content in Cu/Sn/Ti alloy should be less than 21 wt pct in order to maintain proper wettability of the braze. In addition, Cu/Sn/Ti alloys have both lower wetting angle on alumina and lower thermal expansion coefficients than commercial Ticusil® braze.