Verschleißschutz für Titanbauteile

Wear Protection for Titanium Components The use of titanium and its alloys in the last decades keeps on increasing due to its material‐specific characteristics like high firmness, good corrosion characteristics and very high thermal maximum stress. However nowadays, the use of titanium components in systems where wear resistance is important is limited by titanium’s relatively low wear resistance. Surface wear is in principle a characteristic, conditioned by chemical and physical effects of the elements involved as well as collective stress. The necessity for new systems where good wear resistance and excellent mechanical properties are combined keeps on showing up. Due to titanium’s tendency to react with surrounding media, titanium alloys are difficult to be welded. Embrittlement by admission of hydrogen and oxygen can occur at high temperature processes or even changes on titanium’s microstructure may appear. Brazing techniques, which are actually applied to steel, have been modified and adapted for using them to titanium materials. Here, commercially available braze pastes and hard materials where combined and applied on titanium.     

Modifizierte Nickelbasisstandardlote für korrosiv belastete Bauteile

Modified nickel based standard brazing filler metals for units under corrosive loads Nickel‐based alloys are presently used as brazing filler metals for components which undergo mechanical stress in corrosive conditions, f. e. heat exchangers. When soldering chrome containing steel parts with nickel based brazing filler metals additionally containing boron and silicon a reaction of chrome and boron can occur. This evolution of chromium borides, depositing on grain boundaries, causes a lack of chrome in the steel part. A drop of the chrome content in the parts below 13 % leads to a loss of corrosion resistance. It is possible to change the microstructure of brazing joints by modification with chromium and molybdenum. Continuous brittle phases could be successfully avoided with this modification. Furthermore it could be shown that the choice of additives, the heating respectively cooling rate and the brazing temperature have important influence on the microstructure evolution and therefore on the mechanical and corrosive properties of joints.     

Betrachtungen zum Löten in Gegenwart und Zukunft

Consideration on brazing and soldering today and in future In all parts of industries using metals, the application of brazing and soldering is increasing. The origin of those technologies is assumed 6.000 years ago, and for a long time, they were limited to a few industrial fields only. In recent years, they turned out to become a source of innovation. Today, they are essential in different industries as microelectronics, electrical engineering, automotive industry, aviation industry, turbine industry or tool industry. Starting with defining brazing and soldering, especially in comparison to competitive joining techniques, some selected developments of the last decades are presented, as brazing of Aluminium, High Temperature Brazing and brazing of ceramic materials. Finally, an outlook is given concerning ongoing and future developments.     

Diffusionslöten von Aluminium mittels PVD applizierter Lotzusatzwerkstoffe

Diffusion brazing of aluminium by PVD applied filler metals Diffusion brazing of aluminium and aluminium alloys precoated with filler metal components enables fluxless wetting and obtains braze joints of high strength at moderate brazing temperatures. Previously deposited components of filler metals on the base materials as thin film, using Arc‐PVD‐process lead during a subsequently diffusion brazing process to the formation of a local liquid phase (transient liquid phase). The liquid phase is formed from the deposited thin film material and the base material and is solidified isotherm due to diffusion procedures. In doing so braze joints of higher melting point than brazing temperature can be realised. In this work, vacuum brazing of the two systems, Al‐Cu and Al‐Cu‐Si have been investigated. Cu and Al‐Cu‐Si were deposited on the base material using Arc‐PVD‐process. The base materials were pure aluminum and EN‐AW6060. Metallographic and scanning electron microscope analyses proved that the braze seam area after the completed diffusion brazing process shows similar structure and composition as the base material.     

Flussmittelfreies Hartlöten unter reaktiver Prozessgasatmosphäre – ein alternatives Verfahren zum Fügen von Aluminiumwerkstoffen

Flux‐free brazing under reactive process gas atmosphere – an alternative process for joining of aluminium materials Due to the high affinity of aluminium towards oxygen, joining of aluminium materials has ever been a challenge. In particular the efficiency of the process and the abandonment of fluxes during controlled atmosphere brazing have been within the focus of current research projects. The specific addition of reactive gases to the inert process gas atmosphere offers a suitable possibility of aluminium brazing without the use of fluxes. Under the application of hydrogen chloride the activation of the brazing and the workpiece surfaces is to be initiated, thus leading to dissolving the oxide layers. Moreover, the strongly reducing gas silane is used, which specifically removes oxygen and water residuals from the controlled atmosphere. Through a suitable controlled atmosphere brazing process the combination of both, reductive and activating additions, is to be used and tested upon their influence on the gas mixtures and materials used [1–5].     

钛合金与不锈钢焊接研究现状及发展趋势

钛-钢异种金属的连接在航天航空以及化工领域得到了越来越广泛的应用,解决两种金属的连接问题,是其满足实际应用的关键。本文综述了钛-钢钎焊存在的问题并对钛-钢钎焊用钎料及钎焊方法作了简要的概述和分析,最后指出了有待深入研究的问题。     

Joining of zirconia to metal with Cu–Ga–Ti and Cu–Sn–Pb–Ti fillers

The method of brazing by capillary impregnation of Cu–Ga melt through a titanium powder layer situated between brazed details is elaborated. Samples of ZrO₂ ceramic/metal brazed joints using Cu–Ga–Ti filler and Cu–Sn–Pb–Ti filler were fabricated. The joints’ shear strength was 277±37 MPa for the Cu–Ga–Ti and 156±25 MPa for the Cu–Sn–Pb–Ti.     

钛合金与铝合金异种金属钎焊的研究进展

钛合金在经济性和加工性方面不理想,导致其在实际工程应用中受限,而铝合金在某种程度上可以弥补这种缺陷,因此将钛合金和铝合金复合使用的构想应运而生。对钛合金和铝合金异种金属的可焊性进行了分析,以钛合金和铝合金钎焊为研究对象,重点论述了钛合金与铝合金钎焊连接所用的钎料及工艺等的国内外研究现状,并着重分析了Al基和Zn基钎料的润湿性、界面、钎缝组织及其优缺点。由相关文献分析可知,Al基钎料在真空、保护气氛或非真空外加辅助措施条件下对钛合金和铝合金都有良好的润湿性,但接头强度仍有待提高,金属间化合物较厚的问题需要通过优化钎料成分和焊接工艺进一步改善;Zn基钎料对钛合金的润湿性较差,但在适当的焊接工艺下可以获得力学性能较好的Ti/Al接头,剪切强度可达141MPa;使用Sn基和Cu基钎料获得的Ti/Al接头的力学性能低于Al基和Zn基钎料,且Sn基的钎料对两种母材的润湿性都较差,需要对母材表面进行预处理。     

Erforschung Ti–Co‐basierter,bioaktiver Auftraglötschichten auf oxidischen Hochleistungskeramiken in der Medizintechnik

The demand of prostheses and implants made from biomaterials grows as a result of the rising age of patients. For biomaterials, such as those found in joint‐ or hip‐prostheses, that are in direct contact with the organism, not only mechanical stability is required, but also biocompatibility as well as their ability to support bone regeneration. Taking this into account, a thin‐walled bioactive titanium cobalt‐based brazing coating on high‐performance oxide ceramics (Al₂O₃) has been developed. Here, the coating process offers an economical and at the same time technologically simple way for the coating ceramic materials. The biocompatible coating has been enhanced by addition of bioactive particles made of bioglass and calcium phosphates in order to improve bone formation. The reactions between the bioactive particles and the brazing alloys, as well as the particular melting behavior, were determined through thermo analytical methods. The structures of the brazing alloys enriched with bioactive particles were investigated through metallographical methods. The combination of three bioactive additives and two brazing alloys were analyzed in terms of their melting behavior and the resulting porosity, the parameters of the brazing process have been gradually optimized. The results show, that the combination of calcium phosphate particles and Ti–Co alloys effectively meet the requirements for a defined porous, biocompatible brazing coating.     

航空航天领域常用高温钎料研究现状

近年来随着航空航天工业的发展,各类飞行器核心功能部件面临着使役环境愈发极端化的问题。超高速、高温等服役环境对各类零部件的整体性能提出了更高的要求,因此针对航空航天领域用高温钎料的研究尤为重要。在航空航天领域常用的高温钎料包括镍基钎料、钴基钎料、钛基钎料、锰基钎料、贵金属钎料和高熵钎料等,通常应用于不锈钢、高温合金、钛合金以及新型陶瓷材料等的钎焊连接。主要针对在航空航天领域中常用的几种高温钎料,对钎料的元素组成和特性进行总结,对钎料的成形特点和工艺进行介绍,对研究和应用现状进行分析,并对航空航天领域的钎料与钎焊技术提出建议与展望,以期为提升钎焊技术在航空航天领域的应用价值提供参考和指导。     

PTLP Joining of Al2O3-Stainless Steel 304 Using Ni-Cr Foil—The Microstructure Morphologies of Joint Interfaces

Partial-transient liquid-phase brazing of Al₂O₃-stainless steel (SS) 304 using a Ni-Cr foil as a refractory layer in brazing filler metals was investigated in a vacuum environment, and the microstructures in the joints were studied in detail. The cross-sectioned microstructures at joint interfaces show multilayered structures. Six characteristic zones can be distinguished in the joint, named as base alumina zone, titanium reaction zone, roughly homogenized filler materials zone, discontinuous precipitation zone, metallic brazing zone, and base metal zone. The main corresponding phases of these six zones are Al₂O₃(I), TiO+CuTiO₄(II), Ni(Cu)-Cr-Ti(III), Ni(Cu)-Cr+Ti+Fe-Ti(IV), SS304 (V, VI), respectively. Experimental results demonstrated that the formation of TiO and CuTiO₄can improve greatly the wettability of Al₂O₃, and, thus, the good joint was obtained at the interface of Al₂O₃and filler metal. Part of the Ti atoms can diffuse into the interface between SS304 and filler materials and form intermetallics, which precipitate as hard and brittle precipitation during the cooling stage.     

贵金属钎料爆缝金相样品的制备

根据制备Au,Ag和Pd基钎料钎焊不同母材的焊缝金相样品的特点,提出了可以得到清晰的贵金属合金钎料焊缝显微组织的方法,并给出了实验结果。     

Effects of Al2O3 Particulates on the Thickness of Reaction Layer of Al2O3 Joints Brazed with Al2O3-Particulate-Contained Composite Filler Materials

In order to understand the rate-controlling process for the interracial layer growth of brazing joints brazed with active composite filler materials, the thickness of brazing joints brazed with conventional active filler metal and active composite filler materials with different volume fraction of AI203 particulate was studied. The experimental results indicate although there are Al2O3 particulates added into active filler metals, the time dependence of interracial layer growth is t^2 as described by Fickian law for the joints brazed with conventional active filler metal. It also shows that the key factor affecting the interracial layer growth is the volume fraction of alumina in the composite filler material compared with the titanium weight fraction in the filler material.     

Einflüsse auf die mechanischen Eigenschaften lasergelöteter Mischverbindungen aus Stahl und Aluminium

Influences on the Mechanical Properties of Laser Brazed Hybrid Joining of Steel and Aluminium Within the scope of a fundamental research project, a laser brazing process has been developed, enabling the joining of aluminium to steel sheet metal. By applying zinc‐based solders, melting the edges of the aluminium sheets can be reduced to a minimum compared to concurring joining processes. This leads to an excellent joining strength, with tearing in the aluminium base metal as shown by tensile tests. Moreover, the joined material can be formed into hollow parts, with few limitations. There is a great potential for applying this process, for example in car production, resulting from, among other things, high process automation possibilities.     

Al-Ti异种合金真空钎焊的研究

在结合界面上生成层状的脆而硬的金属化合物（TiAl3,TiAl和Ti3Al)是Al-Ti异种合金焊接所存在的主要问题,本工作基一协内外研究成果和相关资料,利用正蛟设计在理,以Al-11.5Si近共晶合金为基,通过添加元素Sn和Ga形成9种钎料,并利用各新钎料对Al合金和Ti合金进行了真空钎焊,勇于强度试验和铺展性试验,对该9种钎料进行评定,试验结果表明,含10％Sn,0.20%GAa的Al-11.5Si铝基钎料铺展性和抗剪强度等方面都具有较好的性能,使Al-Ti异种合金构件达到较好的机械性能。     

Continuous Fiber Reinforced Titanium Matrix Composites: Fabrication,Properties, and Applications

Titanium matrix composites (TMCs) have been developed as high performance materials for light weight structural applications. The materials are comprised of a silicon carbide (SiC) fiber embedded in a titanium matrix, thus making use of the high strength of the SiC fibers, their high stiffness and creep resistance at elevated temperatures combined with the damage tolerance of titanium alloys. Since materials properties are closely related to the quality of the fabrication process, TMC processing is of major importance. Moreover, reinforcement‐induced anisotropy of the material and thermal residual stresses formed during the consolidation process must be considered and understood for proper component design. Finally, modeling using FE methods reduces the time needed for component development and helps to elucidate failure mechanisms of the material.     

Infrared brazing Ti-6Al-4V and SP-700 alloys using the Ti-20Zr-20Cu-20Ni braze alloy

Great efforts have been made in brazing high-strength α-β titanium alloys below their beta-phase transformation temperature in order to obtain optimized mechanical properties. The brazing temperature of the cold roll-bonded Ti-20Zr-20Cu-20Ni foil is roughly 70 °C lower than that of Ti-15Cu-15Ni filler metal. Moreover, the detrimental Cu-Ni and Cu-Ni-Zr rich Ti phases can be greatly reduced or eliminated by properly choosing the brazing thermal cycle. This research demonstrates the potential application of Ti-20Zr-20Cu-20Ni foil in brazing titanium alloys.     

Modellierung der Stängelkristallitbildung beim Hartlöten von Kohlenstoffstählen mit Kupfer

Simulation of columnar crystallite formation in brazed seams of copper‐brazed carbon steels When brazing steels of different carbon content with copper filler metal, columnar crystallites form on the carbon‐rich iron surface if the width of the brazing gap is smaller than 100 μm. Braze seams with such microstructures were described as early as the 1950ies and it was found out, that the strength of such a joint is significant enhanced, if this crystallites penetrate the entire seam. Extensive experimental investigations in recent years confirm, that the final average length of the crystallite increases superproportionally with decreasing brazing gap width and is almost inversely proportional to the difference in carbon content of the joined steels. Although many attempts to explain this phenomenon are known from literature, the mechanism of columnar structure formation has not been clarified properly until now. The aim of the present work was to develop an appropriate physical model, that describes the growth of crystallites as a function of carbon content in the base materials, the initial brazing gap width and the applied process parameters (temperature, time). The model is an appropriate tool for a general choice and development of filler metal‐base material combinations forming columnar crystallites in the braze seam.     

Development of low‐melting‐point filler materials for laser beam brazing of aluminum alloys

In order to develop low‐melting‐point filler materials for laser beam brazing of aluminum alloys, Al–Si–Cu based alloys and Al–Si–Zn based alloys were produced via spray forming and associated deformation processes. The selected alloys were spray formed in the form of billet with a diameter around 160 mm and hot extruded into wire rods with a diameter of 8 mm. The extrusions were further cold worked into thin wires with a diameter of 1.2 mm via rotary swaging. Finally, the filler wires were applied in the laser beam brazing of AA6082 structures. It showed that the newly developed filler materials could meet the requirements of the laser beam brazing of aluminum alloys. Particularly, the laser beam brazing process using the spray‐formed filler materials required a significantly lower energy input and allowed for higher brazing speed as compared to the conventional AlSi12 filler material.     

Löten von Diamant – Grenzflächenreaktionen. und Benetzung

Diamond Brazing – Interfacial Reactions and Wetting Diamond tools are increasingly gaining importance as cutting materials for various construction materials. The quality of synthetic diamonds, monocrystalline as well as polycrystalline or CVD‐diamonds has been significantly improved over the last years. Integrating these cutting materials requires adequate joining technologies that produce sound joints without exposing the temperature sensitive diamond to too elevated temperatures. The paper highlights current developments in the joining of synthetic diamonds to steel and cemented carbide. Owing to their covalent atomic bonding diamonds cannot easily be wetted and joined by employing conventional brazing alloys. Hence, active agents are needed to foster an interfacial reaction. Different active filler concepts are presented and discussed regarding their joint formation. The brazing temperatures influence not only possible diamond degradation but also the interfacial decomposition of the diamond due to the formation of corresponding reaction layers.Active brazing, monocrystalline