Papers by Keyword: Brazing

Abstract: Diamonds films have characteristics that are interesting for many optical applications, such as transparency to ultraviolet, visible and infrared light. These applications include use in detectors and windows in processes that involve high temperatures, microelectronics applications and wear-resistant components [. Polycrystalline diamond films can be made in the vapor phase at low-pressure, relatively low temperatures and in the form of auto-supported films, using the CVD process (Chemical Vapor Deposition) [. These films have a significant number of industrial applications, but often have problems with adhesion to metallic substrates. Diamond films can be deposited directly over some metals, but other techniques, such as brazing, can be used [.

Abstract: The stirring assisted brazing of SiCp/A356 composites with a large size of diameter in air was investigated. A first stirring was applied in brazing of the composites at 470°C. Then, it was continuously heated up to 510°C. Then, a secondary stirring with a large size (2.4mm) diameter was introduced in process. It was found that a composite joint reinforced with SiC particles can be obtained by stirring at 510°C. The experiment result shows that micro-hardness of joint brazed by 2nd stirring is obviously higher than that of joint brazed without 2nd stirring. Moreover, micro-hardness of the upper part of joint is slightly higher than that of the bottom part.

Abstract: High-temperature brazing molybdenum using palladium and titanium foils have been investigated in the experiment. Successful brazed joints are achieved from using the palladium filler foil. Brazed joints are fully dense and free of any intermetallic phase. Three point bending strengths of 246 and 233 MPa are obtained from joints using 100 m thick palladium filler foil brazed at 1580 and 1610 oC for 600 s, respectively. The application of palladium filler foil shows potential in brazing molybdenum for high-temperature application.

Abstract: Tricone drill bits with hard ceramic inserts are often used in oil well drilling operations. However, the cutting action and breakdown of the rock formation produces failures on the tricone bits, which mainly are related to wear, partial or total rupture of the drill bit body or ceramic inserts, thermal shock, and corrosion. Brazing is a well established technique to joint metal-metal, ceramic-ceramic and ceramic-metal materials. Wetting phenomena plays an essential role in the production of metal/ceramic interfaces if a liquid phase is present. Stabilized zirconia with yttria and magnesia can be an interesting material for hard ceramic inserts application on drill bits when oil well or the drilling fluid has acid characteristics. In this work, silver based brazing alloys were melted onto zirconia substrates under high vacuum. The effect of oxide stabilizers and the metallized surface on the wetting behaviour were studied. Better results were found for the yttria stabilized zirconia system using AgCu with 3% Ti as filler alloy.

Abstract: Intermetallics and superalloys brazing development is a current topic owing the extending use of these alloys in industrial applications. In this work a γ-TiAl alloy was joined to Inconel 718 by active metal brazing, using Incusil-ABA as filler. Joining was performed at 730 °C, 830 °C and 930 °C, with a 10 min dwelling time. The interfaces were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD). For all processing conditions, the reaction between the base materials and the braze alloy produced multilayered interfaces. For all processing temperatures tested (Ag), (Cu), AlNi₂Ti and AlCu₂Ti were identified at the interface. Raising the brazing temperature increased the thickness of the interface and coarsened its microstructure. The increase of the extension of the interface was essentially due to the growth of the reaction layers formed near each base material, which were found to be mainly composed of intermetallic compounds. The mechanical behavior of the joints, at room temperature, was assessed by microhardness and shear tests. For all processing conditions the hardness decreases from periphery towards the Ag-rich centre of the joints. Brazing at 730 °C for 10 min produced the joints with the highest average shear strength (228±83 MPa). SEM and EDS analysis of the fracture surfaces revealed that fracture of joints always occurred across the interface, preferentially through the hard layer, essentially composed of AlNi₂Ti, resulting from the reaction between Inconel 718 and the braze alloy.

Abstract: A series of Al-Cu-Si alloys were melted and spun into ribbons of about 100m thickness. The alloy compositions were selected to be suitable for brazing below 580C as filler metals. In the as-quenched state the foils were relatively brittle due to the occurrence of metal metastable phases. After appropriate annealing treatments between 400~450C the metastable phases were transformed into fine (Cu2Al) particles within the -Al matrix, and the mechanical properties of the Al-Cu-Si alloy ribbons were considerably improved.

Abstract: The effect of high welding speed on the macro-appearance and microstructure of joints were investigated in this paper. Experimental results are shown that bonding at one side of joint interface is obviously better than that at another side of bond interface. When welding speed is up to 72mm/min, a discontinuous joining interface is found. It is indicated that increasing of welding speed will be not in favor of disruption of oxide film on surface of composites.

Abstract: C/C composite and TC4 alloy were successfully brazed using 70Ag28Cu2Ti (wt. %) as filler metal at brazing temperature 820 º°C~920 °C for soaking time 5 min ~30 min. The effects of brazing parameters on the microstructures and phase composition and the fracture modes of the brazed joints were investigated by SEM and XRD. The mechanical performances of the brazed joints were measured by a universal mechanical testing machine. The results show that the maximum shear strength of the brazed joint is 28 MPa at brazing temperature 860°C and soaking time 10min. Fracture surface analysis of the brazed joints indicates that the position of the fracture surface is related to the orientation of carbon fiber. The brazed joints are fractured in the C/C composite when the carbon fiber is parallel to the joined surface, and the brazed joints are fractured at the C/C composite / 70Ag28Cu2Ti interface when the carbon fiber is vertical to the joined surface.

Abstract: The custom-designed amorphous brazing filler metals in foil form has been developed for application in brazing stainless steel 0Cr18Ni9. The new alloys contains 10.5wt% chromium, 5.4wt% silicon, 1.5wt% boron, 3wt% cobalt and nickel as the balance. The melting range is within 971°C1070°C. The alloy exhibits good melting characteristics and wetting behavior. With a 25μm thick foil, the joint is free of brittle central eutectic phases inside the joint via diffusion of the alloying elements into adjoining base metal and results on a high mechanical joint strength.

Abstract: In this paper, the effect of different Ti content on the brazed joint microstructures was studied, including the reaction zone states, microstructures of the reaction interface on both ceramic and Invar alloy side. The added Ti content was 2%, 3%, 5%, 6% and 10%. The results showed that Ti had great effect on the thickness of reaction layer on the invar alloy side. Ti can inhibit the growth of the diffusion layer.