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United States Patc?F 2 ‘ Forms a New Lattice Structure United States PatC?f 2 ‘_ forms a new lattice structure. This isshown by X-ray' 2,982,619 di?raction tests which show the disilicide pattern present, " and silica. .When the reaction is run’ in a vacuum or a NIETALLIC COMPOUNDS FOR USE IN HIGH reducing or: inert atmosphere, the excess silicon appears TEMPERATURE APPLICATIONS ' as silicon and not as silica. I , Roger A. Long, Bay Village, Ohio This inventor has produced the molybdenum disilicide (1782 Knoxville St., San Diego, Calif.) in powdered form for use in molding various articles by No Drawing. Continuation of application Ser. No. the di?erent methods of powder metallurgy. He ob . 177,548, Aug. 3, 1950.v This application Apr. 12, 1957, tained the disilicide in powdered form by mixing‘ one 10 equivalent of _ powdered molybdenum with two mols; Ser. No. 652,358 ' ~ . equivalents of powdered silicon (325 mesh size), thor _ .8 Claims. (Cl. 23-204) oughly mixing this mixture as in a ball mill, removing the mixture from the ball mill and heatingv the stoichiomet; ‘(Granted under Title 35, US. Code (1952), sec. 266) rically proportioned ?ne mixture in air, vacuum or inert‘, This invention relates to metallic compounds which 15 gas atmosphere until an exothermic reaction occurred’; are characterized by a relatively high melting point, i.e. A suitable v'essel‘of refractory material, such as a crucible‘ relatively high refractoriness, and by resistance to oxida ' or boat of alundum, beryllia, etc., may be used for hold tion and abrasion at elevated temperatures. In particu~~ ing the powder mixture which is produced in the 'furnac'eQ This reaction took place at about l900° F.:L100° F. with lar the invention relates to inter-metallic compounds of 20 silicon with certain metals of the fourth and’ sixth groups a subsequent temperature rise to about. 3000° F. The of the periodic table of the elements. More-speci?cally powder was then crushed, ball-milled and leached withd the invention relates to an inter-metallic compound of ' concentrated nitric acid ‘to remove any unreacted molyb molybdenum di-silicide and to its properties and uses. denum metal and with hot hydrochloric acid to remove any molybdenum oxide. Leaching is not necessary“ The general object of the invention is to produce an 25 inter-metallic compound or an intermediate solid solu when reacting in a vacuum or gas atmosphere. It was tion of silicon and a metal selected from the group con found that the silicon volatilized at the reaction tem1 " sisting of uranium, molybdenum, chromium, tungsten, ‘ perature under a vacuum; that it was necessary to carry? zirconium, and titanium by a novel method of heat. the reaction to completion in a partial pressure atmos- phere of argon or helium when such gas was introduced treatment. / 30 It is a further object of the invention 'to produce an into the vacuum to furnish up to one half to three inter-metallic compound of silicon with one of the above . quarters atmospheric pressure. de?ned metals which is relatively refractory and resistant The molybdenum disilicide produced by this method‘ ‘to abrasion at high temperatures. ' was not fused; it was friable and was readily ground to a It is a particular object of the invention to produce an desired ?neness by/ball-milling or other particle reduc inter-metallic compound of silicon and molybdenum in ing methods. This grinding will be described herein which these components are combined in the stoichio after. 1 ' metric proportions of molybdenum di-silicide (Mosiz). vIt was also discovered that a mass of high-purity pow It is an additional object of the invention to produce der of molybdenum disilicide (Mosiz), ?ne particles; a di-silicide of molybdenum which by methods of pow without addition of any generally used binder substances, der metallurgy may be molded and shaped into products such as, cobalt, nickel, or the like, will when compacted that are resistant to oxidation, are of accurate dimensions under pressure and heat by known powder metallurgical and relatively high mechanical strength. ' techniques yield a cemented body of substantially pure An object also is to provide a composition formed by molybdenum disilicide (Mosiz) exhibiting extremely de a mixture of a di-silicide of a metal selected from the 45 sirable hot, physical and mechanical properties, which group consisting of uranium, molybdenum, chromium, combined with its ‘superior corrosion resistance makes it tungsten, zirconium, and titanium, with other metals, ideal for applications such as gas-turbine buckets, ?ame semi-metals, oxides, carbides, borides or other silicides. holders and the like. \ ‘_ - V An additional object of the invention is to produce a This inventor produced the disilicides of metals other~ than molybdenum by this direct reaction method. In compound of silicon having high corrosion and wear 50 resistant properties. particular he produced the disilicides of uranium, chro Prior scienti?c and patent literature contains various mium, tungsten, zirconium, and titanium. These silicides suggestions for the production of molybdenum disilicide. vary from one to the other in their physical properties However as far as the inventor is aware, there was not and construction. They vary in refractoriness and in re- ' sistance to oxidation at high temperature. But all are available up to the present time a simple process for 55 producing molybdenum disilicide of relatively high purity useful in certain applications. in a form in which it could be readily comminuted into A second method of powdered metal preparation in ?ne particles for use in producing by powder-metallurgy which powdered molybdenum disilicide, prepared as i technique shaped cemented bodies of great hot strength above described, is impregnated with other metals such as copper, nickel, cobalt, etc. or other alloys, such as and corrosion resistance. 60 The present invention is based on the discovery that, “Colomonoy No. 6,” Phosphor bronze, etc. In. this‘ when a stoichiometrically proportioned intimate mixture method of preparation these additive metals and alloys of ?ne particles of molybdenum and silicon, correspond are drawn into the'skeleton of the molybdenum disilicide ' ing to the formula Mdsiz, is heated to an elevated tem to form’ an intimate material. These alloys are not as ‘ refractory as the molybdenum disilicide alone, but they perature of about 2000° R, which is well below the melt 65 ing point of these components, a reaction takes place are useful for the reason that they can be readily worked between them which results in the production of rela ‘by the process of “hot forming” i.e. “hot coining.” Y . tively pure molybdenum disilicide in a friable form which These disilicides may be considered ‘as being inter may be readily comminuted into ?ne powder particles metallic compounds or metal compound phases. Broadly ' they are intermediate solid solutions some of which have ' suitable for powder metallurgy processing. The reaction 70 of the silicon with the molybdenum is exothermic and wide and others narrow ranges of homogeneity. ‘Since 1 the .temperaturerises to about 3000“ F. Thesilicon re true intermetallic compounds have narrow rangesmof ho acts with the molybdenum throughout the mass and 5 mogeneity and simple stoichiometric- proportions with i a aesae 1e 3 4 atoms of identical kinds occupying identical points on the ' (3) Vacuum casting. lattice, all of the disilides of this invention cannot be (4) ‘Hot coining. classed as true intermetallic compounds. They are all (5) Swaging and rolling. intermediate solid solutions and some of them, for ex The formed material canbe machined and brazed to ample,‘ USi-é, WSig, TiSi2, CrSi2, and ZrSi2 may be, of the ?nal required forms by methods such as: , either type, particularly ZrSiz and TiSiz which apparently (1) Grinding, diamond or gravity fed silicon carbide have wide range of homogeneity and can contain excessive wheel. V ‘ silicon and/or excessive zirconium in solution with the (2) Machining, using‘ carbide tools (only when in a disilicide. ‘ partially sintered condition). But in the case of titanium disilicide, the theoretical 10 ( 3) Brazing, using silver, copper or colomonoy alloys. analysis of which is: ' PRODUCTION OF ARTICLES BY THE METHODS Titanium ~ _______________________________ __ 46.05 OF POWDER METALLURGY 7 Silicon ___ 53.95 As stated above, the production of articles ‘by the methods of powder metallurgy can be accomplished by 100.00 ?ne basic methods. The V?rst of these, cold press and the analyses of powdered silicides, prepared as above sinter, because of its extensive use industrially will be described gave the following: discussed ?rst. The cold press and sinter method I II 20 This method is now used commercially in the fabrica Titanium; ...................................... _. 49. 0 44. to tion of cemented carbides. This method, with some modi Silicon. - . ____ _- 47. 3 50. 30 ?cation, can be used for the making of articles from the Iron 1. 04 Aluminum--. _ . 95 powdered disilicides of this invention and particularly for Other Impurities ................................ __ 3. 7 3. 60 25 the molding of powdered molybdenum disilicide. 100. 00 100. 00 In this process cold pressing is accomplished by the use of properly shaped permanent dies and applied pres In neither case are the titanium and silicon present in sure. The dies are oversized to allow for shrinkage dur the theoretical proportions. Thesecompounds, however, ing sintering. The pressure used varies with the shape showed goodqresults at elevated temperatures and must be 30 of the work, the organic binder used, and the compacting considered only as intermediate solid solutions. necessary for good, green, mechanical strength. The pres Tungsten disilicide, as produced by the method of this sure must be uniformly applied over thcentire die in inventor is a true intermetallic compound, checking very order to increase the resistance to possible later thermal close to stoichiometric proportions.
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