Development and evaluation of braze alloys for vacuum furnace brazing
Copper and copper-base alloys tested for use in vacuum furnace brazing of rocket engine tubular thrust chambers
ROCKET CHAMBER↗
SEARCH · Engineering Papers
Results for “vacuum furnace brazing”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Furnace brazing under partial vacuum
Brazing furnace utilizing partial-vacuum technique reduces tooling requirements and produces better bond. Benefit in that partial vacuum helps to dissociate metal oxides that inhibit metal flow and eliminates heavy tooling required to hold parts together during brazing.
Mckown, R. D.↗
Diffuser Braze Development
At the request of SRTE, through the PDRD project, SRNL is developing a vacuum brazing process to facilitate the fabrication of hydrogen purification systems. In particular, this effort is directed at tube-style hydrogen diffusers. The diffusers are comprised of numerous palladium-silver tubes that are brazed to a nickel fitting, which is subsequently welded to a stainless steel tube, fitting, or tube sheet. Historically, torch brazing has been used as a heat source; for this work vacuum furnace brazing was suggested to improve the uniformity of the process. This report describes the braze process development for braze selection and simple nickel fitting to tube brazing. Five braze alloys were selected and sessile drop testing was conducted over a range of temperatures from 25 to 75° C over the liquidus temperature. Samples were characterized for wetting angle, erosion, and brazability. The cup-to-tube braze joints were inspected using digital radiography, ultrasonic testing, and metallographic examination. Two of the five alloys exhibited excellent fabrication properties and are considered for further development.
36 MATERIALS SCIENCE↗
Uniform-Dead-Weight Brazing
Method of deadweight loading for vacuum-furnace brazing improves quality of joint, increases yield, and reduces costs. In improved method, plates weighted with heavy stainless-steel blocks. Blocks act independently and are immune to distortion. Besides being uniformly distributed, force applied to plates larger and repeatable from one brazing operation to next. Larger blocks used on edges of plates, where more thermal mass needed to reduce differences between temperatures of interior and edge as temperature of furnace varied.
Gaw, William D.↗
Ultraminiature Broadband Light Source and Method of Manufacturing Same
An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light ource is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.
Tuma, Margaret L.↗
Ultraminiature broadband light source with spiral shaped filament
An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light source is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.
Tuma, Margaret L.↗
Braze alloy holds bonding strength over wide temperature range
Copper-based quaternary alloys of the solid solution type is used for vacuum furnace brazing of large stainless steel components at a maximum temperature of 1975 deg F. The alloy has high bonding strength and good ductility over a temperature range extending from the cryogenic region to approximately 800 deg F.
Source record↗
Brazing of refractory, superalloy, and composite materials for Space Shuttle applications.
Research work concerning the metallic portion of the shuttle-orbiter heat shield (expected to experience temperatures up to 2500 F) is described. The five metals being evaluated are TD-Ni-Cr, Cb-C129Y, Cb752, Hayes 188, and Inconel 625. Brazing techniques whereby pairs of these materials are joined into thin-membered assemblies for heat shield applications are described. Results obtained with the vacuum-furnace brazing process are examined. In addition, the use of brazed aluminum-boron metal-matrix-contoured composite structures for heat shield applications is evaluated.
Beuyukian, C. S.↗
An Investigation of High-temperature Vacuum and Hydrogen Furnace Brazing
Explore the source record for details and available documents.
Russell, Walter E↗
Protecting brazing furnaces from air leaks
Inexpensive inert-atmosphere shielding protects vacuum brazing-furnace components that are likely to spring leak. Pipefittings, gages, and valves are encased in transparent plastic shroud inflated with argon. If leak develops, harmless argon will enter vacuum chamber, making it possible to finish ongoing brazing or heat treatment before shutting down for repair.
Armenoff, C. T.↗
Increasing Metal Fracture Toughness
In technique developed at Langley Research Center several thin sheets of metal are diffusion-brazed together in vacuum furnace to create thick piece of metal that retains much of fracture toughness of its thin components. Technique is expected to make many of high-strength stainless steels, not currently suitable, usable at cryogenic temperatures.
Lawing, P. L.↗
Weld-brazing of titanium
A joining process, designated weld-brazing, which combines resistance spotwelding and brazing has been developed at the NASA Langley Research Center. Resistance spot-welding is employed to position and align the parts and to establish a suitable faying surface gap for brazing; it contributes to the integrity of the joint. Brazing enhances the properties of the joint and reduces the stress concentrations normally associated with spotwelds. Ti-6Al-4V titanium alloy joints have been fabricated using 3003 aluminum braze both in a vacuum furnace and in a retort containing an inert gas environment.
Bales, T. T.↗
Passively pumped, polycrystalline ceramic high and ultra-high vacuum chambers
A sealed, passively pumped, polycrystalline ceramic vacuum chamber and method for fabricating the chamber are disclosed. The body of the vacuum chamber is made from a polycrystalline ceramic, for example, alumina. The vacuum chamber includes one or more windows made from a transparent ceramic, for example, sapphire, to accommodate optical access, while remaining amorphous-glass free to minimize or eliminate helium permeation. The vacuum chamber components are joined via laser welding or furnace brazing and the completed chamber is bakeable at temperatures up to 400° C. The vacuum chamber can operate at high or ultra-high vacuum pressures for an extended period through the use of one or more getter-based pumps. The vacuum chamber may include one or more atomic sources depending upon the application.
Walker, Charles A.↗
Design, fabrication, and performance of brazed, graphite electrode, multistage depressed collectors with 500-W, continuous wave, 4.8- to 9.6-GHz traveling-wave tubes
A small, isotropic graphite electrode, multistage depressed collector (MDC) was designed, fabricated, and evaluated in conjunction with a 500-W, continuous wave (CW), 4.8- to 9.6-GHz traveling-wave tube (TWT). The carbon electrode surfaces were used to improve the TWT overall efficiency by minimizing the secondary electron emission losses in the MDC. The design and fabrication of the brazed graphite MDC assembly are described. The brazing technique, which used copper braze filler metal, is compatible with both vacuum and the more commonly available hydrogen atmosphere brazing furnaces. The TWT and graphite electrode MCC bakeout, processing, and outgassing characteristics were evaluated and found to be comparable to TWT's equipped with copper electrode MDC's. The TWT and MDC performance was optimized for broadband CW operation at saturation. The average radiofrequency (RF), overall, and MDC efficiencies were 14.9, 46.4, and 83.6 percent, respectively, across the octave operating band. A 1500-hr CW test, conducted without the use of an appendage ion pump, showed no gas buildup and excellent stability of the electrode surfaces.
Ramins, Peter↗
More About Brazing Or Welding NiAl Without Filler
Two reports present additional information about two processes for joining, brazing, or welding workpieces made of nickel aluminide alloys, without use of filler metal. Joining processes involve uniform heating in vacuum-controlled furnace. Eliminates internal thermal gradients in workpieces joined and greatly reduces tendency toward cracking.
Moore, Thomas J.↗
New space processing experiments for the Skylab missions.
The M512 Materials Processing Facility, which is the main item of equipment for the Skylab space manufacturing experiments is described. It is basically an electron-beam welding apparatus, consisting of a battery power supply, a 20-kV electron beam source, and a spherical 40-cm-diam vacuum chamber. It will be used to perform the M551 Metals Melting Experiment, the M552 Exothermic Brazing Experiment, the M553 Sphere Forming Experiment, the M554 Composite Casting Experiment, the M555 Gallium Arsenide Crystal Growth Experiment, the M561 Whisker-Reinforced Composites Experiment, the M562 Indium Antimonide Crystal Growth, Experiment, the M563 Mixed III-V Crystal Growth Experiment, the M564 Alkali Halide Eutectics Experiment, the M565 Silver Grids Melted in Space Experiment, and the M566 Copper-Aluminum Eutectic Experiment. Three apparatus systems designed to broaden the technical scope of the experiments and to gain experience with new experimental techniques are described. These are an electrophoretic separator, an electromagnetic levitation system, and a versatile electric furnace with an electronic control system.
Bredt, J. H.↗
Improved Blackbody Temperature Sensors for a Vacuum Furnace
Some improvements have been made in the design and fabrication of blackbody sensors (BBSs) used to measure the temperature of a heater core in a vacuum furnace. Each BBS consists of a ring of thermally conductive, high-melting-temperature material with two tantalum-sheathed thermocouples attached at diametrically opposite points. The name "blackbody sensor" reflects the basic principle of operation. Heat is transferred between the ring and the furnace heater core primarily by blackbody radiation, heat is conducted through the ring to the thermocouples, and the temperature of the ring (and, hence, the temperature of the heater core) is measured by use of the thermocouples. Two main requirements have guided the development of these BBSs: (1) The rings should have as high an emissivity as possible in order to maximize the heat-transfer rate and thereby maximize temperature-monitoring performance and (2) the thermocouples must be joined to the rings in such a way as to ensure long-term, reliable intimate thermal contact. The problem of fabricating a BBS to satisfy these requirements is complicated by an application-specific prohibition against overheating and thereby damaging nearby instrumentation leads through the use of conventional furnace brazing or any other technique that involves heating the entire BBS and its surroundings. The problem is further complicated by another application-specific prohibition against damaging the thin tantalum thermocouple sheaths through the use of conventional welding to join the thermocouples to the ring. The first BBS rings were made of graphite. The tantalum-sheathed thermocouples were attached to the graphite rings by use of high-temperature graphite cements. The ring/thermocouple bonds thus formed were found to be weak and unreliable, and so graphite rings and graphite cements were abandoned. Now, each BBS ring is made from one of two materials: either tantalum or a molybdenum/titanium/zirconium alloy. The tantalum-sheathed thermocouples are bonded to the ring by laser brazing. The primary advantage of laser brazing over furnace brazing is that in laser brazing, it is possible to form a brazed connection locally, without heating nearby parts to the flow temperature of the brazing material. Hence, it is possible to comply with the prohibition against overheating nearby instrumentation leads. Also, in laser brazing, unlike in furnace brazing, it is possible to exert control over the thermal energy to such a high degree that it becomes possible to braze the thermocouples to the ring without burning through the thin tantalum sheaths on the thermocouples. The brazing material used in the laser brazing process is a titanium-boron paste. This brazing material can withstand use at temperatures up to about 1,400 C. In thermal-cycling tests performed thus far, no debonding between the rings and thermocouples has been observed. Emissivity coatings about 0.001 in. (.0.025 mm) thick applied to the interior surfaces of the rings have been found to improve the performance of the BBS sensors by raising the apparent emissivities of the rings. In thermal-cycling tests, the coatings were found to adhere well to the rings.
Farmer, Jeff↗