Brazing interface silver filler
102647936
The dissimilar brazing of Kovar alloy to SiCp/Al composites using silver based filler metal foil
Aluminum metal matrix composites with high SiC content (60 vol. SiCp/Al MMCs) were surface metallized with a Ni P alloy coating, and vacuum brazing between the composites and Kovar alloy were performed using rapidly cooled Ag 22.0Cu 15.9In 10.86Sn 1.84Ti (wt% foil. The effects of Ni P alloy coating and brazing parameters on the joint microstructures and properties were researched by SEM, EDS, and single lap shear test, respectively. Results show that Ag Al intermetallic strips were formed in the 6063Al matrix and filler metal layer because of diffusion, and they were arranged regularly and accumulated gradually as the brazing temperature was increased (T/degC 550 600) or the soaking time was prolonged (t/min 10 50) However, excessive strips would destroy the uniformity of seams and lead to a reduced bonding strength (at most 70 MPa) Using a Ni P alloy coating, void free joints without those strips were obtained at 560 degC after 20 min soaking time, and a higher shear strength of 90 MPa was achieved. The appropriate interface reaction ~2 mm transition layer) that occurred along the Ni P alloy coating/filler metal/Kovar alloy interfaces resulted in better metallurgical bonding. In this research, the developed Ag based filler metal was suitable for brazing the dissimilar materials of Ni P alloy coated SiCp/Al MMCs and Kovar alloy, and capable welding parameters were also broadened.
Po Fang Wang Dongxia Xu Yahong Zhai Ji-tai Niu
139325650
Laser Brazing of a Hexagonal Boron Nitride Block to a Cemented Carbide Plate with Silver Copper Titanium Alloy Filler in Argon Atmosphere Including Different Oxygen Contents
Relationship between oxidation of Ag Cu Ti braze alloy and oxygen contents was investigated in the laser brazing of a hexagonal boron nitride block to cemented carbide plate in Ar atmosphere. The laser brazing was conducted in Ar flow atmosphere in a vacuum chamber, and changing Ar flow rate with and without pre evacuation. No oxidation of the braze alloy was found after 3 min Ar flow atmosphere over 5 L/min without pre evacuation and at 5 L/min with pre evacuation. When the Ar flow rate increased to 10 L/min without pre evacuation, the oxygen content decreased to 3.8 ppm. In this case, the average shear strength of the brazed joint was about 8 MPa and a fracture occurred at the hexagonal, boron nitride side of the specimen, near the interface.
Sechi Yoshihisa Nagatsuka Kimiaki Fujimoto Takahiro Tsukamoto Masahiro Nakata Kazuhiro
215818249
Effect of Electroless Ni P Plating on the Bonding Strength of PbTe Thermoelectric Module Using Silver Alloy Based Brazing
This study investigates a brazing method for manufacturing PbTe thermoelectric modules using a Ag based filler metal with a melting point of about 650 degC. To improve the bonding strength between the Ag based brazing layer and the PbTe thermoelectric module, an electroless Ni P plating layer is formed on the surface of the thermoelectric module as a diffusion barrier layer. The bonding strength of the PbTe thermoelectric module manufactured by the electroless Ni P plating and Ag based brazing has a high value of approximately 8.3 MPa. No defects such as pores or cracks were observed at the bonding interface between the thermoelectric element and the brazing layer. Furthermore, because of the high bonding strength of the manufactured thermoelectric module, fractures occur inside the thermoelectric element rather than at the bonding interface. Accordingly, the electroless Ni P plating and Ag based brazing method proposed in this study is found to be effective in manufacturing PbTe based thermoelectric modules with high bonding strength.
Sung Hwa Bae Joon-Young Choi Injoon Son
53242993
Joining of TiAl Alloy Using Novel Ag Cu Sputtered Coated Ti Brazing Filler
Abstract The aim of this study is to evaluate the potential use of titanium foil coated with sputtered silver and copper films as a novel brazing filler for joining TiAl alloys. For this purpose, a detailed microstructural characterization of the resulting brazing interfaces was carried out. The development of brazing fillers that allow the joining of TiAl alloys without compromising the service temperature is a fruitful prospect. Brazing experiments were performed in a vacuum at 900, 950, and 980degC, with a dwell time of 30 min. Microstructural characterization reveals that brazing joints can be obtained successfully at 950 and 980degC. The interface consists of a large central region of a Ti with an amount of Al and Ti Ag compound and thin layers, mainly composed of intermetallic compounds, formed close to the base material. A novel brazing filler consisting of Ti foil coated with sputtered Ag and Cu films inhibits the extensive formation of soft (Ag) zones or coarse brittle Ti Al (Cu,Ni) particles. Hence, the need for post brazing heat treatments for the joining of TiAl alloys was avoided.
Microscopy and Microanalysis
Sonia Simoes Ana Soares Carlos Jose Tavares Anibal Lopes Guedes
108287421
Effect of Composition on the Corrosion Behavior of Stainless Steels Brazed with Silver Base Filler Metals An electrochemical galvanic action between coexisting phases is responsible for the corrosion of filler metal and interface
The effect of composition of silver base filler metals and austenitic stainless steels on the corrosion of stainless steel joints brazed with silver base filler metals was investigated in aqueous sodium chloride solution. The depth of corrosion in the filler metal increased with the increase of zinc content in filler metal and (Ni Cr) content of base metal. The interfacial corrosion was promoted by the increase of silver content in the filler metal. The phenomena are explained by the galvanic cells such as the stainless steel bulk surface/a Cu phase in filler metals, and the a r A g phase/active stainless steel at the braze interface. The brazing flux leaves the active layer at the braze interface by the removal of protective passive films; this is believed to be one of the causes of interfacial corrosion. A nickel depleted ferrite phase is observed at the interface brazed with nickel free filler metals; however, the formation of a nickel depleted zone is prevented by the use of filler metals with 2% Ni. Addition of nickel to filler metals is found to prevent the formation of the less corrosion resistant nickel depleted zone.
Tadashi Takemoto Ikuo Okamoto
136098939
Interface Characteristics and Mechanical Properties of the Vacuum Brazed Joint of Titanium Steel Having a Silver Based Brazing Alloy
The lap joint of a commercially pure titanium plate (CP Ti) to a low carbon steel plate was produced with a vacuum brazed furnace using a silver based filler alloy at different temperatures and lap widths in order to investigate the effects of such brazing parameters on the joint strength and structure. It was found that the shear strength of brazed joints depends strongly on the lap width. Furthermore, we have discovered that the shear strength of the joints increases as the lap width decreases. The maximum shear strength of the joints, 54 MPa, was obtained when they were brazed at 850 degC for 15 minutes. Our observations indicate that intermetallic compound layers of CuTi and Cu2Ti were formed at the interface of the brazed area. An increase in the brazing temperature led to increased growth of these layers. Shear tests show that the fracture path occurred mainly at the CuTi layer, because this layer is hard and brittle.
Ahmed Elrefaey Wolfgang Tillmann
214380523
Joining of stainless steel (SS304) and OFE copper by vacuum brazing
Abstract This paper describes the vacuum brazing process for joining OFE copper with stainless steel (SS 304) using silver based filler material (68Ag27Cu5Pd) Vacuum brazing of SS304 and OFE copper was carried out in a vacuum furnace at a vacuum level of 10 6 mbar. The peak brazing temperature was kept as 920 degC with a soaking time of 10 min. This combination is often used in bi metallic joints for high vacuum applications. Optimization of brazing parameters was done to produce defect free joints. Micro structural analysis of the brazed joint was carried out using optical and scanning electron microscope. The flow of filler material and diffusion of its elements into substrates was observed. The brazed joint was found to be of good quality and free from any major cracks. The micro hardness was evaluated across the interface and it was observed that hardness decreases towards the interface. The hermeticity of the joint was investigated using helium spray method.
Vikas Mangla Sandeep Kumar P K Dinesh Kumar Arun Agarwal
137859750
Effect of Brazing Filler Metal on Joining and Microstructure of Interface of Zirconia Ceramic/Ag CuO
Brazing of ceramics by CuO Ag in the air was investigated in this study. Twelve kinds of brazing filler metals were selected. The microstructure,elements distribution and phase of brazing joint were investigated by metallographic examination(SEM,EDX,XRD).The result indicated that the addition of CuO substantially improve the brazing performance of Zirconia ceramic substrates by silver in the air. In the interface of brazing joint,there was a black transition. The layer was considered CuO and Ag by XRD and EDS. The joint was effected by the CuO content of filler metal.When the CuO content of filler metal was 34mol%,the microstructures and constituents were homogenous,the distribution and the solution of elements were best,the distribution distance of Cu and Ag was 50mm and the interface zone was the best widest.
Liang Lina
137410100
Silver nanoparticle assisted diffusion brazing of 3003 Al alloy for microchannel applications
Abstract In the current study, we investigated the effect of braze filler particle size and various processing parameters on vacuum diffusion brazing of thin foils of 3003 Al using a Ag nanoparticle (AgNPs) interlayer. All samples were brazed at 550 degC and 570 degC at heating rates of 5 degC/min and 25 degC/min under a pressure of 1 MPa. Differential scanning calorimetric results, involving 5 nm AgNPs, showed significant reduction in phase transformation temperature. Microstructures of brazed cross sections revealed that nanoparticles aid formation of the joint at temperatures below the Al Ag eutectic temperature of 567 degC. X ray diffraction analysis of the interface showed the presence of d phase (Ag 2 Al) and m phase (Ag 3 Al) This was confirmed with energy dispersive spectroscopic analysis. A tensile strength of 69.7 MPa was achieved for a sample brazed at 570 degC with an interlayer of approximately 7 mm in thickness.
Ravi Eluri Brian K Paul
137533411
Interfacial microstructures and bonding strength between aluminum nitride and silver brazing filler metals containing various active elements
Effect of active element on interfacial microstructures and bonding strength of brazed AIN/AIN joints has been investigated and compared with the case of brazed Si 3 N 4 /Si 3 N 4 joints. Brazing was carried out at 1173 to 1473 K for 3.6 ks in a vacuum using Ag Cu filler metals containing Ti, Zr, V and Nb as an active element. The obtained joint had no defects such as un bonded areas, regardless of active element and bonding temperature. Four kinds of active elements were divided into two groups by shear tests and microstructural observations. One was Ti and Zr, and the other was V and Nb. The bonding strength of the former was higher than that of the latter. In particular, the joint with Ti addition showed an excellent strength of about 200 MPa. Main fracture position in the joints with Ti and Zr additions was within the AIN, while most joints with V and Nb additions broke at the interface between the active filler metal and the AIN. In the former, TiN and ZrN layers consisting of fine grains were observed adjacent to the AIN. On the other hand, the joint with Nb addition had roundish grains of Nb 2 N in similar locations. It was considered that the existence of fine grains contributed to the enhancement of bonding strength due to the increase of contact area and to the formation of complicated interface. These tendencies were essentially consistent with those of the brazed Si 3 N 4 /Si 3 N 4 joints.
Yasuhiro Morizono Minoru Nishida Akira Chiba Takashi Nakata