Engineering topics
Publications and source records attributed to Buckman, R. W., Jr..
Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.
The vacuum arc casting of tungsten alloys, which contain carbon as an alloy addition, require special melting procedures in order to produce melts of consistent controlled levels of alloy content. A melting procedure will be described in which elemental components of a tungsten 0.35% HfC alloy are assembled to form an electrode for ac vacuum arc melting to produce 3-in.-diam ingots. Melting procedures and analytical chemistry are discussed and compared with data for ingots produced by other techniques.
Metallurgical condition was shown to have a significant effect on the creep properties of ASTAR-811C (Ta-8W-1Re-0.7Hf-0.025C) sheet. Cold worked material exhibited creep rates 30 times higher than solution annealed material and 10 times greater than for recrystallized material. Both grain size and the carbide morphology changes as the final annealing temperature was raised from 3000 F to 3600 F. However, the lowest creep rates were achieved for material which retained the high temperature form of the Ta2C precipitate. Samples with GTA weldments had essentially identical properties as recrystallized base metal. Cooling rates from 3600 F of 5, 50, and 800 F deg/min. had little effect on the 2000 and 2400 F creep behavior of ASTAR-811C.
Five experimental tantalum alloy compositions containing 13-18% W+Re+Hf solid solution solute additions with dispersed phase strengthening achieved by carbon or nitrogen additions were prepared as 1.4 inch diameter ingot processed to 3/8 inch diameter rod and evaluated. Elevated temperature tensile and creep strength increased monotonically with increasing solute content. Room temperature elongation decreased for 20% to less than 2% as the solute content was increased above 16%. Phase identification indicated that the precipitating phase in the carbide containing alloys was Ta2C.
Mechanical properties of precipitation strengthened tantalum base alloys
Mechanical properties determined for precipitation hardened tantalum base alloy /ASTAR-811C/ for potential use in Rankine cycle nuclear power systems
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Large diameter T-111 tubing processed from seamless and welded tube shells
Three experimental tantalum alloy compositions containing 14-16% W, 1% Re, 0.7% Hf, 0.025% C or 0.015% C and 0.015% N were prepared as two inch diameter ingots by consumable electrode vacuum arc melting. The as-cast ingots were processed by extrusion and swaging to one inch and 0.4 inch diameter rod and evaluated. Excellent high temperature forging behavior was exhibited by all three compositions. Creep strength at 2000 F to 2400 F was enhanced by higher tungsten additions as well as substitution of nitrogen for carbon. Weldability of all three compositions was determined to be adequate. Room temperature ductility was retained in the advanced tantalum alloy compositions as well as a notched/unnotched strength ratio of 1.4 for a notched bar having a K sub t = 2.9.
Evaluation of refractory/austenitic bimetal combinations
Creep properties, brittleness, hardness, and microstructure of dispersion strengthed tantalum base alloys
Grain size and annealing temperature effects on creep properties of dispersion strengthened tantalum base alloys
Dispersion-strengthened tantalum-base alloys possess high strength and good resistance to creep deformation at elevated temperatures in high vacuum environments. They also have ease of fabrication, good weldability, and corrosion resistance to molten alkali metals.
Dispersion strengthened tantalum base alloys for use in advanced space power systems
Dispersion strengthened tantalum base alloys - continued development in test program
Compatibility of explosively bonded refractory austenitic bimetal composites after isothermal and cyclic thermal exposure
Dispersion strengthened tantalum base alloys - development with evaluation of oxygen contaminated and welded compositions
Welding, aging, and oxygen contamination effects on dispersion strengthened tantalum base alloys