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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.
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Plating process welds, bonds, and seals refractory metals without weakening or changing the structure of the base metals. A metal halide compound in the vapor phase is decomposed to deposit filler metal on the base metal. The resulting bond is a true metal-to-metal bond.
Solubility of refractory metals and alloys in liquid potassium and lithium
Refractory metals interactions with gases in vacuum and inert gas environment, noting temperature and pressure effects on reactions, extent and kinetics
Contamination of refractory metals by oxygen, water vapor, and carbon monoxide
High temperature oxidation resistant coatings for superalloys, refractory metals, and graphite
Performance characteristics of iridium used as high temperature oxidation protective coating for refractory metals
Effects of hydrostatic pressure cycling on mechanical behavior of body centered cubic refractory metals and alloys - quench aged condition study of iron-carbon alloys
Refractory metal heat pipes developed during this project shall be subjected to various operating conditions to evaluate life-limiting corrosion factors. To accomplish this objective, various parameters shall be investigated, including the effect of temperature and mass fluence on long-term corrosion rate. The test series will begin with a performance test of one module to evaluate its performance and to establish the temperature and power settings for the remaining modules. The performance test will be followed by round-the-clock testing of 16 heat pipes. All heat pipes shall be nondestructively inspected at 6-month intervals. At longer intervals, specific modules will be destructively evaluated. Both the nondestructive and destructive evaluations shall be coordinated with Los Alamos National Laboratory. During the processing, setup, and testing of the heat pipes, standard operating procedures shall be developed. Initial procedures are listed here and, as hardware is developed, will be updated, incorporating findings and lessons learned.
Hydrostatic pressure effect on mechanical behavior of body centered cubic refractory metals and alloys
Fused salt electrodeposition and examination of iridium protective coatings on tungsten, molybdenum, and niobium
Space power system material compatibility tests of selected refractory metal alloys with boiling potassium
Hydrostatic pressure on mechanical behavior of body centered cubic refractory metals and alloys
Carbon activity in refractory metals
Effective work functions of refractory metals at temperatures near their melting points were determined by using a direct-current arc. A metal wire connected as the cathode was melted by striking an arc discharge in an argon atmosphere. A melted sphere was formed with a definite emitting area which was calculated from the sphere diameter measured after terminating the arc. Effective work functions were calculated from the Richardson-Dushman equation by using this emission area. The procedure is experimentally advantageous because surface cleanliness of the specimen is not critical, high vacuum is not required, and the anode-cathode spacing is not critical.
The performance was determined of refractory metal alloys and uranium nitride fuel element specimens in flowing 1900F (1083C) lithium. The results demonstrate the suitability of the selected materials to perform satisfactorily from a chemical compatibility standpoint.
Tensile strength and thermostability of welded refractory metal joints
High temperature protective coatings for refractory metals
The objective of this research was to demonstrate that the damage tolerance of Si 3 N 4 could be significantly improved by forming laminate composites with refractory metals, providing materials that undergo graceful failure, rather than the fast-fracture mechanism exhibited by monolithic Si 3 N 4 . A damage tolerant Si 3 N 4 could be used as a ring material in an all-ceramic bearing, decreasing the chance for catastrophic failure if the ring is stressed in tension during operation. The technical approach formed a laminate composite material using alternating Si 3 N 4 -metallic layers, with both outer layers being Si 3 N 4 to take advantage of its greater wear resistance, chemical stability, and thermal stability. The metallic layers are designed to arrest any cracks in the outer layers, thus producing a toughened Si 3 N 4 and avoiding the catastrophic failure behavior exhibited by monolithic ceramics. The laminate composites were fabricated using a combination of tape-casting Si 3 N 4 and metals from slurries, as well as metal foils, followed by hot pressing at 1500°C. The metallic materials employed were chromium, titanium, and tantalum. Analysis confirmed that the interfaces were well formed, and the laminates with chromium and titanium formed intermetallic compounds more readily than the composites with tantalum. The Si 3 N 4 -Ta laminates demonstrated crack deflection and bridging behavior during failure and flexural strength of 800–900 MPa. The hardness and elastic modulus of Si 3 N 4 -Ta laminates measured by nanoindentation were similar to those reported in literature. The hardness across the interface of the Si 3 N 4 -Ta composite varied according to the composition of the interface, which displayed a profile indicative of a diffusion bond.