July 17, 1962 M. G. WHITFIELD ETAL 3,044,156 , TEMPERATURE RESISTANT BODY Filed June 25, 1954

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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. Of course, in point on the surface. .For example, samples treated'iby actual manufacture, layer 11 is initially a coating of alumi >the method of the invention have been heated Vto tempera num containing sometungsten or molybdenum and is ‘ Atures a hundred degrees C. above the normal .boiling point ' bonded to the core by an aluminum rich alloy of these Yof'aluminum before the aluminum boiled away, indicat 25 refractory metals caused by partial diffusion of the alumi „ing that the alloysof aluminum with tungsten or molyb num into the core. In service, or in the final stage of denum'have extremely high Vboiling or sublimationpoints. manufacture, the excess `aluminum is partly oxidized and Likewise, it has been found'that the presence Vof aluminum partly diffused to produce the ­alloy surface layer which is on thesurfaceofthesemetals, will permit their­ use for referred to in the foregoing. K .applications requiring substantial strength at `elevated tem 30 FIG. 2 illustrates an example of the modification of the peratures. The method of the invention is applicable with 'invention in which the tungsten or molybdenum core 20 is equal or similar results also to alloys of at least one of first coated with a thin iilm of nickel or other iron base the metals iron, nickel, cobalt with tungsten or molyb metal 2l and thereafter is exposed to the eñect of a molten denum, or'both, containing substantial quantities of tung bath of aluminum base material, such as, for example, sten ormolybdenum, such as at leastl 15% by weight, Vand 35 commercially pure aluminum, thereby forming a protec~ Valso to alloys of tungsten and molybdenum. , tive layerZZ onV the exterior Aof the core. As arresult of v Preferably, the aluminum coated tungsten and molyb the interaction of the core material With that of the layers denum containing bodies are ,heat treated'to assureV the ' `21 and 22 during the heating and coating'treatments and formation lofa high melting compound of aluminum with subsequent service operation, the metal body is converted ­the tungsten or molybdenum core and thereby .to obtain 40. into the one shown in FIG; 3 wherein the individual a completely stable product. Itis also possible, however, existence` of ’layers Zyl and 22~has practically disappeared, to omit-such' heat treatment and‘to rely on the diffusion such layers being combined intoa layer 23` which is com of the aluminum coating into Áthe refractory core during.V posed of an alloy rich in aluminum and-containing ap 'the actual operation at elevated temperatures. .If 'heat preciableamounts of nickel and tungsten or molybdenum. treatment is resorted to, the heat treating temperature may 45 While in the drawing fragmentary sectional views of Abe in the order of 1300" C., although it is not restricted 1 refractory metal strips are shown which are coated with to 'such temperature. a layer of aluminum base material on both facesthereof, .'"While­ the methodoffthe invention providesV excellent v. in actual practice, the refractory metal> bodies are pro results in protecting and stabilizing tungsten and molyb-` " vvidedwith a_ protective layer of the described character denum bodies, when .treating these metals with `alumi 50 throughout their entire surface, including their ends and num or its alloys, occasionally small spots or areas are edges. ï In this manner, the said metal bodies are fully found which are ralloyed only with extreme ditiiculty. VWe protected from Ydeterioration at elevated operating tem .have found that 4this diñiculty may be »completely avoided '.peratures. by electrodepositing a thin film Vorrlayer of nickelron the In order to facilitate understanding of the invention V,surface of ther tungsten or molybdenum and diffusing or Y ‘by those skilled in Athe art, the following illustrative exam at leastheating the nickel plated sections in a non-oxidiz ples may be given: . ing or­ reducing atmosphere at approximately .l000° C.y Example I ` 'before treating the sections of tungsten or molybdenum Y ‘with’ aluminum. This modification of the methodl of the A molybdenum sheet 0.015" thick, mill finish, was im ¿invention provides in moist cases more uniform; protection 60 mersed in a bath of molten commercially pure aluminum ‘or alloying of the aluminum with thebase metals. ' ' having a temperature of 720° C., for 6 minutes. After The thickness of the electrodeposited> nickel layer is­ v removal from the bath and cooling, the materialwas not criticaland maybeasubjected‘ to considerable Vvaria tested by heating it to 1400-1500° C. in an oxidizing tions. In this connection, it may be observed that dijlîu atmosphere> for 4 hours, without noting `any appreciable l sion of the nickel layer maybe accomplished not only by deterioration. ' ‘heating under non-oxidizing conditions but also by heat ' Example II ` ing in an oxidizing atmosphere providedthat suthcient4 _A. molybdenum sheet about 0.020" thick was cleaned nickel is present. As a matter of fact, electroplating with> and a light coating of nickel was electrodeposited thereon. nickel maybe immediately followed by thelalurninum 70 The plated sheet was heated for a few minutes in a reduc coating treatment. In this case, diifusion of the nickel ing atmosphere at approximately 1000" C. The sheet was ` layer is accomplished by the heating eiîect of the bath of .cooled and then treated by immersing in a bath of molten aluminum base material, and the bath _at the same time commercially pure aluminum, having a temperature of provides the non-oxidizing or protective environment. 740° C., for 3 minutes. ' ‘It has been found that nickel is not the only metal which 75. Although the present invention has been described in 3,044,156

5 , 6 . connection with a few preferred embodiments thereof, aluminum alloy' and the base 'metal is equally veffective variations and modifications may be resorted by those with beryllium alone or with valuminum »alloys containing skilled in the art without departing from the principles of beryllium or beryllium and silicon. ` . ' the invention. Thus, as it has been indicated in the fore~ In the production of coated bodies having a minimum going, the principles of the invention are not restricted to 5 difference between the coefficients of expansion of the the treatment of tungsten and molybdenum bodies but bodies `and the coatings thereon, it is possible not only to may be applied with equal or similar results to metal diminish the coeñicient of expansion of the coatings, but bodies composed of alloys of tungsten and molybdenum also to raise the coetiicient of expansion of the bodies. with each other or with other metals. The advantages of . Where tungsten and molybdenum bodies are spoken of the invention in the case of tungsten and molybdenum above, not only are bodies of pure molybdenum or tung alloys are particularly accentuated when such alloys con sten or mixtures of the two contemplated, but »also ternary tain at least 15% by weight of tungsten or molybdenum, or complex alloys containing at least substantially 15% or tungsten and molybdenum combined. of tungsten or molybdenum or a mixture of the two. The The teachings hereinabove made and the `examples coefficient of expansion of such ternary or complex alloys hereinabove given, applying to the coating of tungsten or is higher than that of molybdenum or tungsten alone. But molybdenum bodies (as defined) with aluminum or it is possible to raise the coetlìcient of expansion of such aluminum alloys (as deñned), apply as well to the use bodies by alloying the molybdenum or tungsten or ternary of the metals silicon and beryllium as constituents of the >alloys containing them with such elements as chromium. initial coating. One of the purposes of the present inven This may ordinarily be done without sacriñce of desirable tion is to avoid extraordinary discrepancies between the 20 physical properties. coefficients of expansion of the base metal and the coating When coating tungsten or molybdenum or »ferrous material. As compared with aluminum which has a high bodies with beryllium or aluminum alloys containing coefficient of expansion, tungsten and molybdenum bodies beryllium, a protective `atmosphere will normally be main have relatively low coeihcients of expansion. tained over the bath'since beryllium is more subject to it has hitherto been known that the alloying of rela 25 oxidation than aluminum. tively large quantities of silicon with aluminum will pro Modiñcations may be made in the invention without vide a metal composite having a relatively lower coeñicient departing from the spirit of it. The invention having of expansion, and in particular a coefficient of expansion been described in certain exemplary embodiments, what substantially closer to that of ferrous bodies. For such is claimed as new and desired to be protected by Letters purposes, as much as from 25% to 30% or more of 30 Patent is: . silicon has’been alloyed with aluminum. l. A body formed from metal chosen from a class It has been found, however, that such very large quanti consisting of tungsten, molybdenum, mixtures of the two, ties of silicon give an aluminum alloy material which is Kand ferrous alloys containing »at least 15 % of any of the more difficult to use in molten `form as a hot dipping medi foregoing, bot coated with a bonded layer of aluminum um, and also that the formation of an adequate bond be 35 containing substantially 5% to 50% beryllium. tween the alloy layer and ferrous base metals is rendered 2. A body formed from metal chosen from a class more diñîcult. consisting of tungsten, molybdenum, mixtures of the two, ’ Beryllium is a metal which has a coetiicient of expan~ 'an-d ferrous alloys containing at least 15% of anyy of the sion substantially less than half that of aluminum. We foregoing, hot coated with a bonded layer of'aluminum have found that beryllium may be alloyed withaluminum 40 containing substantially 5% lto 15% beryllium, and sub to provide alloys having coetlîcients of expansion much stantially 5% to 15% silicon. closer to that of ferrous bodies and tungsten and molyb­\ 3. As a new article of manufacture, a refractory metal denum bodies as herein deñned. When beryllium is tbody protected from surface deterioration Iat lelevated added to aluminum, it is readily possible to secure coating operating temperatures comprising la core constituted of alloys having coeiiicients of expansion very much lower a refractory metal selected from the group consisting of than that of aluminum alone, and in particular coefficients tungsten, molybdenum, alloys of tungsten and molyb of expansion substantially corresponding with those of denum, and alloys containing at least 15% of any of the conventional ferrous bodies, with the beryllium within the ranges set forth above, namely from about 5% to about foregoing with at least yone of the metals iron, nickel, 15%, and up to about 50% of the alloy. cobalt and chromium, »and `a protective »layer on said core It is readily possible to employ beryllium along with of aluminum containing substantially 5% to 15% beryl silicon., For example, an alloy can be formed of alumi lium. . \ num containing about 5% to 15% of beryllium and 5% 4. As a new `article of manufacture, Áa refractory metal to 50% silicon, balance being aluminum. body protected from surface deterioration at elevated Beryllium in substantial quantities thus is seen to be a operating temperatures comprising -a core constituted of valuable component of aluminum or aluminum alloys used a refractory metal selected from the group consisting of for coating where the object is to attain in the coating a tungsten, molybdenum, alloys of tungsten and molyb coeñ’icient of expansion much more nearly corresponding denum, and `alloys containing at least 15% of any of the to that of the base metal, whether the base metal is to 60 foregoing with Áat least one of the metals iron, nickel, be coated by hot dipping or by the casting of the alumi-` cobalt and chromium, Iand `a protective layer on said core num alloy against it. Moreover, beryllium has a sub of aluminum containing substantially 5% to 15 % beryl stantially lessened tendency to interfere with the forma lium, and substantially 5% to 50% silicon. tion of a strong bond between the aluminum alloy and 5. The structure claimed in claim 3, with >a thin inter- ' the base metal upon which it is coated. face layer of nickel between the body and the protective In the formation of tungsten or molybdenum bodies layer. , which are to withstand oxidative deterioration at the high 6. The structure claimed in claim 4, with a thin inter temperatures mentioned herein, the beryllium does not face layer of nickel between the said body and the said interfere with the action hereinabove described. In fact, protective layer. tungsten and molybdenum bodies, resistant to oxidative deterioration at high temperatures, can be produced by 70 7. A tbody formed from metal chosen from a class con coating tungsten or molybdenum bodies . (as deiined) sisting of tungsten, molybdenum, mixtures of the two and with beryllium alone, in spite of the high avidity of the ferrous alloys containing at least 15% of any of the fore last named metal for oxygen. The use of interface going, hot coated with a bonded layer of beryllium. A metal coatings as hereinabove disclosed between the 75 (References on following page) 3,044,156

_ _ S ` _ Y 'Y , ff Referençes' cited in the fue df this patent Y ‘ Y2,135,652, Whi§ñe1d'______Nov. 8, 1938 2,565,768 Sittings ______Aug. 28, 1951 _ VUNITEDswmgs VPATENTS, ’ ' , 2,588,421 , v Shepard ______,Mar. 11, 1952 `Mmlß: _____‘•_.'._.~.______' Sept. n 28, 1915 1,155,317 ' 2,665,475 Campbell ______.. Ian. 12, 1954 1,716,943 Archer ___.._,__'_..l______June 11, 1929 2,682,101 Whitñeld ______June 29, 1954 V1,860,793 Weiger ______May 31,1932 . >1,879,748 Y VHorsíìelcl ______Sept. 27, 1932 FOREIGN PATENTS 2,062,329 Nook ______' Dec. 1, 1936 2,096,924 Schwarzkopf ___-_,___~___ Oct. 26,l 1937 240,411 Great Britain ______July 8, 1926 _ 2,121,084 y Kruh ______June 21, 1938V 723,418 ' >_Frame ______Apr. 8, 1932