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BY” /Crwe @Hfs/,Layoff MQW ATTORNEYS July 17, 1962 M. G. WHITFIELD ETAL 3,044,156 , TEMPERATURE RESISTANT BODY Filed June 25, 1954 EGJ. W @I 7ô/vcsrf/v v@ A404. raaf/VUM IN VEN TCR3 . M45/,WzL @Marr/:za BY” /crwe @Hfs/,layoff MQW ATTORNEYS. r ‘ ßßdlhß United States Patent O ” ice j Patented July l?, 1962 i. 9 atmospheres-which is simple in character and which may 3,û4ßi,156 readily carried out on a practical and industrial scale at TEMPEEE‘ATURE RESÍSTANT BÜDY lvlarshall G. Whitêeld, 2 Harvard St., Garden City, NX., low cost. , ' ' and Victor Sheshnnoii‘, PÃ). Box '702, l‘viagnelia, Ark. The invention­ also contemplates a new article of Fiied .inne 23, 1954i, Ser. No. 438,652 manufacture in the form of a refractory metal body 7 Ciaiins. ttll. 29-194) protected from oxidic surface deterioration comprising a core of tungsten or molybdenum, or alloys thereof with The present invention relates to improved metal bodies each other or with other metals, and a protective layer constituted of tungsten or molybdenum and ferrous al coated on said core. .. " loys thereof, and more particularly to metal bodies con Another object» of the invention is the provision of taining substantial percentages of tungsten and molyb vmeans for avoiding the deterioration of protected bodies denum protected against deterioration inV oxidizing atmos made `of or containing molybdenum or tungster or pheres at high operating temperatures. both due to excessive differences in coeñicients of ex This is a continuation-in-part of our copending ap pansion as between the body and the coating. ­ plication, Serial No. 673,880, filed lune l, 1946, and en Another object of the invention is the provision o tilted “Oxidation Protected Tungsten and Molybdenum coated bodies of the general class herein referred to in Bodies and Method of Producing Same,” which has now which beryllium is a constituent of the body or the coat matured into Patent 2,682,101, dated lune 29, 1954. ing or both. At the present time there are various industrial. de Other and further objects and advantages of the in velopments where alloys of special character are neces~ vention will become apparent from the following descrip sary, capable of retaining their high mechanical strength tion, taken in conjunction with the accompanying draw at high operating temperatures. Examples of such ap ing, in which: ­ - . plications are particularly parts for jet engines and gas FIG. l is a fragmentary sectional vview of a metal body turbines in which the demands made on the structural embodying the principles of the invention during the parts with respect to their strength at elevated operating 25 process of its manufacture. temperatures are extremely exacting. ' FIG. 2 is a similar View of an oxidation protected Materials now employed for these purposes general tungsten or molybdenum body having a bonding layer of ly comprise alloys of iron and of nickel, in many cases nickel and a protective layer applied thereto, and with additions of cobalt, chromium, tungsten and molyb FIG. 3 is a longitudinal sectional view of a refractory denum. Even the alloys of tungsten and molybdenum, 30 metal body comprising a core of tungsten or molyb while theoretically promising, proved very disappointing denum and having a partially `diffused protective layer in actual practice. ln general, few, if any, of these al thereon constituted of an alloy of protective elements loys had a useful life over 300 hours, necessitating fre and molybdenum or tungsten.. quent replacement of critically important structural ele Y Broadly stated, according to the principles of the in ments at great trouble and expense. ~ ' f vention,»the tungsten or molybdenum bodies to be pro As is known, tungsten and molybdenum are unstable tected are .coated preferably with a aluminum base-Ina when heated in air or in any other oxidizing atmosphere terial which maybe pure aluminum or alloys rich in at temperatures in the range of 800° C., or above. The aluminum. This coating may be carried out by various oxides formed on the surface of the tungsten and molyb procedures but best results are obtainedby a hot dip denum bodies under such conditions sublime or boil method in which the metal bodies to `be protected are im away continuously V't0 such a pronounced degree that mersed in a bath of molten metal for a predetermined these metals can only be used in a pure reducing atmos length of time sufficient to provide a coating of the metal phere of hydrogen, or of an inert lgas, such as argon, or thereon. We have found that Í¿by this method there is in vacuum. The same difficulty is present with respect to formed a thin protective layer on the surface of the alloys containing more than 15% of _tungsten and molyb 45 tungsten or molybdenum ‘body which layer is essentially denum. Of course, this circumstance greatly restricted constituted of an alloy of coating metal with the base or even negatived the usefulness or such metal bodies metal. Experimental work with tungsten ~>and molybde and, as a matter of fact, those skilled in the art strongly num bodies treated in accordance with the invention has advised against the use of alloys containing tungsten and indicated that these materials do not exhibit their normal molybdenum in excess of 15% for high temperature ap 50 oxide forming characteristics even at temperatures ap plications. Although the outstanding problem was well proximating the boiling point of aluminum and in many known in the art and from time to time various sugges cases even at vtemperatures as high as 2000° C. tions and proposals were made to provide a solution . The bath of molten aluminum base material may be therefor, none, as far as we are aware, of these sug composed of high purity aluminum, commercially pure ' gestions and proposals was completely satisfactory and aluminum and of aluminum alloys having a relatively successful on a practical and industrial scale. high aluminum content. Examples of such aluminum We have found that the problem may be solved in a alloys are alloys containing 5% to 15% by weight of remarkably simple and unique manner. ~ ' at least one of the elements selected from the group con It is another object of the inventionV to provide a sisting of’iron, nickel, chromium, cobalt and beryllium, novel and improved method of preventing the surface 60 the balance being substantially all aluminum. In ad sublimation and resulting deterioration of metal bodies dition, various other aluminum base materials contain constituted of tungsten, molybdenum, and alloys thereof ing other and further constituents may be used.. when exposed Yto oxidizing atmospheres at elevated tem 'If desired, the bodies to be treated' with the bath of peratures in the range of 800° C. and thereover. molten aluminum base material may be subjected to a It is a further object of the invention to provide a preliminary cleaning by Sandblasting, burnishing and protective layer on the surface of tungsten and molyb similar mechanical procedures. In most cases, however, denum bodies, said protective layer being essentially com such preliminary cleaning is not necessary. For exam posed of an aluminum containing material. ple, rolled molybdenum sheet may be subjected to treat It is also within the contemplation of the invention ment by the bath of aluminium base material without `to provide a novel method of protecting tungsten and 70 any preliminary cleaning. ' molybdenum bodies against surface sublimation at high .The temperature of the bath of molten aluminum base operating temperatures while exposed to oxidizing material may be subject to considerable variations in 3 Aaccordance with its composition. Thus, in the case of is capable of providing this additional protection, but a bath of commercially pure aluminum, temperatures in that in general iron group metals such as nickel, iron, the range of 700° to 800° C. provide satisfactory results. cobalt, chrominum and manganese will accomplish sub The aluminum coating treatment. may be carried out stantially the same result. Moreover, We have found that continuously or by means of a bath type process. Par 5 in many cases copper and silver plates may provide equal 1 ticularly in the case of a continuous process, the treatment or similar results. , tin the molten bath ofv aluminum base material may-vary While the‘exact reason for the beneficial effect `of the from -a few seconds to several minutes depending on the v preliminary deposit of nickel or other iron group metal is Vinitial temperature of the bodies to be treated, on their not fully understood, it is believed that these metals form thickness or mass and to some extent also on the operating alloys with aluminum more quickly than do tungsten and temperature of the bath. The thickness of the coating of molybdenum and that these electrodeposited films act as aluminum basematerial is not critical but may be in the temporary protectors until the aluminum can form its îorder of 0.002." to 0.00.4". alloy with the tungsten or molybdenum which have a ‘ExaminationV of wire and sheet samples of .tungsten tendency to oxidize even at relatively low temperatures, p and molybdenum, which have been treated with aluminum 15 such as red heat." ' _ _ and exposed to„high_temperatures in oxidizing atmos-v Referring now to the drawing, in FIG. l there is shown >-pheres, indîcatestha't a high melting compound of alumi a metal body embodying the principles of the invention ßnum .with the tungsten or molybdenumcorehas been` which comprises a base or core 10 of tungsten or molyb«> ' formed and that this alloy is free from the weúness of denum. Upon both faces .of the core there is provided a ` either thev tungsten or molybdenum with regard to oxidiz thin coating ¿11 of aluminum or aluminum base material ing tov form .a compound of low boiling or sublimation constituting a protective layer _for the core.
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