Metal-to-ceramic seals for thermionic converters - A literature survey

Metal to ceramic sealing techniques for thermionic converters - literature surve

Wetting and Reactivity of Active Metal Braze Alloys on Tungsten Carbide

Background Tungsten carbide is useful because of its hardness and strength. Joining of dissimilar materials especially non-metallic materials is very challenging. Active metals such as titanium can be added to a ductile filler metals such as copper to get wetting via a reduction reaction. Conclusions All alloy conditions wet the tungsten carbide/cobalt substrates. Two different interfacial reaction types were observed: dissolution and reduction reactions. An important issue has been identified: the braze interface reactions change the chemistry of the braze alloy which change the interaction between the braze alloy and the other material substrate.https://digitalcommons.mtech.edu/urp_aug_2014/1000/thumbnail.jp

Joining and Integration of Advanced Carbon-Carbon Composites to Metallic Systems for Thermal Management Applications

Recent research and development activities in joining and integration of carbon-carbon (C/C) composites to metals such as Ti and Cu-clad-Mo for thermal management applications are presented with focus on advanced brazing techniques. A wide variety of carbon-carbon composites with CVI and resin-derived matrices were joined to Ti and Cu-clad Mo using a number of active braze alloys. The brazed joints revealed good interfacial bonding, preferential precipitation of active elements (e.g., Ti) at the composite/braze interface. Extensive braze penetration of the inter-fiber channels in the CVI C/C composites was observed. The chemical and thermomechanical compatibility between C/C and metals at elevated temperatures is assessed. The role of residual stresses and thermal conduction in brazed C/C joints is discussed. Theoretical predictions of the effective thermal resistance suggest that composite-to-metal brazed joints may be promising for lightweight thermal management applications

Study of plate-fin heat exchanger and cold plate for the active thermal control system of Space Station

Plate-fin heat exchangers will be employed in the Active Thermal Control System of Space Station Freedom. During ground testing of prototypic heat exchangers, certain anomalous behaviors have been observed. Diagnosis has been conducted to determine the cause of the observed behaviors, including a scrutiny of temperature, pressure, and flow rate test data, and verification calculations based on such data and more data collected during the ambient and thermal/vacuum tests participated by the author. The test data of a plate-fin cold plate have been also analyzed. Recommendation was made with regard to further tests providing more useful information of the cold plate performance

Study of the state-of-the-art of the hermetic seals for secondary alkaline spacecraft cells Quarterly report, Sep. 20 - Dec. 20, 1967

Manufacturing methods, cost estimates, advantages, and limitations of various types of hermetic seals for secondary alkaline spacecraft cell

Characterization of Brazed Joints of C-C Composite to Cu-clad-Molybdenum

Carbon-carbon composites with either pitch+CVI matrix or resin-derived matrix were joined to copper-clad molybdenum using two active braze alloys, Cusil-ABA (1.75% Ti) and Ticusil (4.5% Ti). The brazed joints revealed good interfacial bonding, preferential precipitation of Ti at the composite/braze interface, and a tendency toward de-lamination in resin-derived C-C composite due to its low inter-laminar shear strength. Extensive braze penetration of the inter-fiber channels in the pitch+CVI C-C composites was observed. The relatively low brazing temperatures (<950 C) precluded melting of the clad layer and restricted the redistribution of alloying elements but led to metallurgically sound composite joints. The Knoop microhardness (HK) distribution across the joint interfaces revealed sharp gradients at the Cu-clad-Mo/braze interface and higher hardness in Ticusil (approx.85-250 HK) than in Cusil-ABA (approx.50-150 HK). These C-C/Cu-clad-Mo joints with relatively low thermal resistance may be promising for thermal management applications

Bonding and adjoining technology: A compilation

This compilation covers NASA and AEC developed techniques covering bonding, brazing, and joining methods and technology

NASA Contributions to Metals Joining

Survey of NASA supported metals joining research having industrial application

Aerospike thrust chamber program

An existing, but damaged, 25,000-pound thrust, flightweight, oxygen/hydrogen aerospike rocket thrust chamber was disassembled and partially repaired. A description is presented of the aerospike chamber configuration and of the damage it had suffered. Techniques for aerospike thrust chamber repair were developed, and are described, covering repair procedures for lightweight tubular nozzles, titanium thrust structures, and copper channel combustors. Effort was terminated prior to completion of the repairs and conduct of a planned hot fire test program when it was found that the copper alloy walls of many of the thrust chamber's 24 combustors had been degraded in strength and ductility during the initial fabrication of the thrust chamber. The degradation is discussed and traced to a reaction between oxygen and/or oxides diffused into the copper alloy during fabrication processes and the hydrogen utilized as a brazing furnace atmosphere during the initial assembly operation on many of the combustors. The effects of the H2/O2 reaction within the copper alloy are described