Bureau of Mines / Minerals yearbook: Metals, minerals, and fuels 1972
Year 1972, Volume 1 (1972)
Stevens, Richard F., Jr.
Tungsten, pp. 1239-1259 ff. PDF (2.4 MB)
TUNGSTEN Materials Science and Technology Division of the American Nuclear Society at the University of Utah in Salt Lake City.a7 Topics covered included fundamentals and techniques of (ND processes, composites, coatings, fibers, and powders; and application. Continuing studies on vapor-deposited tungsten by National Aeronautics and Space Adminisration (NASA) metallurgists at the Lewis Research Center indicated that mechanical properties could be improved by the selective incorporation of various nonmetallic impurties.SS Additional studies of the mechanical behavior of CVD tungsten by University of Utah research metallurgists indicated a lower strength than that of standard powder metallurgy tungsten.39 A way to fabricate complicated tungsten shapes was developed in which gaseous tungsten hexafluoride and hydrogen react at high temperatures to deposit pure tungsten on a copper pipe or mandrel.40 When the copper is etched out, a pure tungsten pipe remains. To eliminate the minute pits and flaws that lower the strength and -increase the rate of rejects in cemented tungsten carbide products, Kennametal developed a process for producing exceptionally highquality cemented tungsten carbide forms by simultaneous application of isostatic pressure of up to 20,000 pounds per square inch, and elevated temperature up to 2,750° F.4' In addition to using hot isostatic processing for bonding and pressing tungsten metal powder in variety of applications, several companies have reported using this process to manufacture tungsten carbides and tool steels.42 Consolidated tungsten metal was produced in good yields on a small scale by aluminothermic reduction of tungstic oxide with small amounts of calcium and sulfur to initiate the reaction at 450° C.43 The aluminum in the consolidated tungsten, which initially contained 1,400 parts per million, 0.14%, was subsequently reduced to 30 parts per million by nonconsumable arc melting. - Submicroscopic gas bubbles trapped in doped tungsten filaments impart greater high-temperature strength to the metal by solid solution or dispersed second phase alloying.44 1259 Tungsten alloys having excellent tensile strength and stress-rupture properties at 1,650° C and 1,920° C were prepared from sintered powder blends of tungsten and tungsten zirconium or zirconium nitride by high-impact (Dynapak) extrusion.4~ The strengthening was attributed to solid solution strengthening by zirconium and by submicron particles of zirconium dioxide. A study of the development of submicroscopic porosity in several grades of doped tungsten wire was conducted in the temperature range between 3,000° and 3,350° C.46 The extremely small submicroscopic pores inhibit - recrystallization and permit development of the interlocking grain structure necessary for sag-resistant filaments. A prototype device was developed for semiautomatic gas tungsten arc welding of small diameter tubing.47 Because the torch nozzle is always centered over the weld joint where the arc is started, the arc length remains constant and arc initiation is easier since the tungsten is preset for the weld. 37 Glaski, F. A. (ed.). Proceedings of the Third International Conference on Chemical Vapor Deposition. Am. Nuclear Society (Hinsdale, Ill.), 1972, 787 pp. 38 National Aeronautics and Space Administration. Nonmetallic Impurities Improve Mechanical Properties of Vapor-Deposited Tungsten. NASA Technol. Brief B72—l0454, August 1972, 1 pp. 39 Chun, J. S., H. S. Shim, and J. G. Byrne. Mechanical Behavior of Chemical Vapor Deposited Tungsten. Met. Trans., v. 3, No. 12, December 1972, pp. 3093—3096. 40 Chemical and Engineering News. Tungsten Shapes. V. 50, No. 27, July 3, 1972, p. 13. 41 Kennametal Inc. Anssual Report 1972, 19 pp. 42 Boyer, C. B. Hot Isostatic Processing. Chem. Eng. Progress, v. 68, No. 5, May 1972, pp. 78—80. The complete 28-page manuscript may be obtained from AIChE Pub. Dept. 345 E. 47th St., New York. 43 Belitskus, David. Aluminothermic Properties of Metals and Alloys. J. Metals, v. 24, No. 1, January 1972, p. 34. 44 Dawson, Chester. Effect of a Temperature Gradient on Bubble Growth in Tungsten. Met. Trans., v. 3, No. 12, December 1972, pp. 3103— 3107. Sell, Heinz G. and George W. King. Bubble Strengthening a New Materials Concept. Res.f Development, v. 23, No. 7, July 1972, pp. 18—21. 45 Blickensderfer, R., M. I. Copeland, and W. L. O'Brien. Strengthening of Tungsten by Powder Metallurgical Internal Oxidation. Internat. J. of Powder Met., v. 8, No. 3, July 1972, pp. 145—155. 46 Brett, J., and S. Friedman. High-Temperature Porosity in Tungsten. Met. Trans., v. 3, No. 4, April 1972, pp. 769—778. 47 National Aeronautics and Space Administration and Small Business Administration. Spinarc Gas Tungsten Arc Torch Holder. Welding Technol., NASA SP—59l8(02), 1973 p. 32. (Available from the National Technical Information Servsce, Springfield, Va.).
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