Coating Tungsten Or Molybdenum With

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. - . v I, 1 I i ~ 2 v FRANK A. FAHRENWALD, OF CLEVELAND, OHIO,‘ DEDICATED, BY MESNE ASSIGN MENTS, TO THE GOVERNMENT OF THE UNITED STATES OF AMERICA. AND TO THE ' PEOPLE OF THE UNITED STATES OF AMERICA. . raoonss or comma rrrmos'rmv on MOL'YBDE‘NUM wrrn NOBLE METALS. Speci?cation of Letters Patent. 1,236,383.. ' Patented Aug. ‘t, 191?. 110 Drawing. Application ?led May .31, 1916. Serial No. 100,999. ' ' (DEDICATED TO THE IPUBLIC.)

To all whom,- it may concern: . _ ‘ quire and ‘wherein that'coating may be as 50 Be it known that I, FRANK A. Fragmen thm as desired with reference to the pur WALD, a citizen of the United States, residlng pose 111 view. Generally speaking my‘ in at Cleveland, in the county of Cuyahoga and vention comprehends the employment of a‘ State of Ohio, have invented a certaln new ?ux of peculiar composition and attributes and useful Improvement in Processes _of which shall contain in itself‘the materials 55 Coating Tungsten or Molybdenum with necessary to cleanse and preserve unoxidized 4 Noble Metals, of which the following 1s a the tungsten metal, and shall itself deposit full, clear, and exact description. _ thereon the desired coating of precious 10 This application is made under the act of ‘metal. ‘In developing the material for this March 3, 1883, chapter 143 (22 Stat. 625) purpose, I havefound that the oxygen salt 60 ‘and the invention herein described and of the alkali metals form the'best ?ux for claimed may be used by the Government of dlssolving the oxid from the surface of the the United States, or any of its o?icers or tungsten ‘or molybdenum. There are a num 15 employees in the prosecution of work for ber of these salts that can be used and any the Government or by any person in the may be chosen which will form an alkali 65 United States without the payment of any tungstate or molybdate by uniting with the royalty thereon. The invention_relates to a oxid of these metals. > I have found that process of coating an easily oxidizable metal sodium‘ carbonate or better still a mixture , 20 like tungsten or molybdenum wlth a. non of this with fused borax serves very satis oxidizable metal such as gold or platinum. factorily for this purpose, although many 70 In my copending applications ?led May 31, alkali salts can be used. 1916, Serial Nos. 100,996 and 100,997 have To this cleansing ?ux I add a salt of a described respectively an article consisting precious metal, for example, chlorid of gold, 25 of a ductile and malleable tungsten _ or palladium, or platinum, or a mixture of any molybdenum base with an adherent coatlng of these in any proportion. Similarly the 75 of gold or other precious metal or alloy, and ?nely divided metals themselves may be in a process of making the same; this process timately mixed with the ?ux and give nearly consisting in the immersion of the artlcle in as good results, although I prefer to employ 30 a bath of molten coating metal whereby a one of their halogen salts from the fact that very heavy coating layer is produced. This segregation before application is less to be 80 method, while resulting in an extremely sat feared than in the case of the metals them isfa'ctory article, was unduly expensive since selves. For operative purposes, however, it the coating of gold or‘ other precious metal is necessary only that some such metals 35 secured thereby was unnecessarily heavy, (either in the combined or uncombined Also if the wire or other article were covered form) be added as will appear in the fused uniformly, as by a continuous process oper metallic condition when the ?ux is ‘applied ation, many parts would receive a coating of and melted under the conditions stated. gold which would not require it, thereby un The use and action of this ?ux combina— 40 necessarily increasing the expense while 1f tion is then essentially as follows: The only certain portions of the article were tungsten or molybdenum metals or alloys are 90 covered the procedure was slow and tedious. heated and dipped into or drenched with the Also the former or dipping process necessi powdered ?ux causing a small amount to tated the fusion of a considerable amount of adhere to the hot surface. Heat in stronger 45 gold which was not always convenient. degree is then applied from a blast lamp or The present invention comprehends a sim blow pipe or other suitable means. As the 95 pler, quicker, and cheaper process for e?ect temperature is raised, the alkali salts melt, ing this coating operation whereby only react with the surface oxid, thoroughly those parts will be coated as need shall re cleansing the metal, upon which is simul ' 1,236,383

taneouslydeposited the metallic content of zation of the tungsten, ‘wherefore its use 68 the ?ux, which has also become molten. In alone is not recommended. Palladium alone the case of the pulverized metal being mixed adheres very strongly and even alloys with the ?ux no chemical change takes place slightly, but also, when used alone, appears therein; in case a combined salt of the vto accelerate ‘crystallization though when precious metal be employed, the temperature used in company with a preponderance of 70 of the operation automatically causes a re gold this deteriorating effect, is not observ duction to take place, which reduction can, able. Gold‘ alone has comparatively little of course, be assisted if desired by the em a?inity for tungsten or molybdenum and the 10 ployment of a suitable reducing agent in line of contact is rather clearly de?ned, the - ?ux. The surface thus receives a though it adheres reasonably well for all __ cleansing and protective treatment practi ractical purposes and forms .a most beauti cally simultaneously, and may then be ul coating without any injury to the metal soldered or brazed by adding ordinary gold beneath. Its adhesion is improved by the 15 or precious metal solders in the usual man addition of ?ve to ten per cent. of palla . ner. It is best to complete the operation by dium, and without inimical eifects upon the adding the required amount of solder and. tungsten so far as can be observed. Metals melting it down with'the ?ux, although the of the platinum group, or'other refractory operation of coating may be performed at precious metals such as iridium, have a 20 any time in advance of the soldering if de marked dissolving effect, so that if a true sired, or the whole operation may be per alloyed bond is desired, one or more ofthese 85 formed with a single heat. Also the entire metals may be employed in connection with tungsten article may be coated if desired, the gold. ‘ or a portion coated and‘the remainder left The metallic content of the ?ux may vary 25 uncoated, suitable means being employed to within very wide limits; I have obtained maintain the temperature of the uncoated perfect (but very thin) protective coatings 9.0 portion sufficiently low to prevent oxidation, with as low as two per cent. of‘ precious or to cover the same with a suitable ?ux so metal in the ?ux, although I prefer to em as to prevent the access of air thereto. The ploy a larger proportion. However by vary 30 temperature of the operation should be ing the constitution of the ?ux it is possible maintained below about 14000 (l, and even to produce a coating of diiferent thicknesses 95 this temperature should be maintained for upon different portions of the article, pro not more than about 10 to 30 seconds in the portioning each thickness to the use or treat case of ductile tungsten or molybdenum ment the article is to undergo, and it will be 35 since a higher temperature or a longer time apparent that very many changes in detail tends to embrittle the metal. Of course of my improved process may be made with 100 lower temperatures can safely be maintained out departing from_ the scope of my inven for a longer time but the time element tion defined in the claims hereto annexed should always be kept as low as convenient. and indicated by the prior state of the art. The particular metal or metals incorpo Having thus described my invention, what rated in the flux can be chosen to meet de I claim is :— - ' 105 sired conditions or to duplicate the solders 1. In the process‘ of soldering oxidizable to be used or precious metals to be united, metals like tungsten or molybdenum the or to secure a predetermined shade of ‘color step which consists in appl ing the molten 45 or a desired melting point or resistance to solder in the presence of a ux containing a chemical action. If it is desired to unite fusible alkali salt and the salt of a noble 110 tungsten to gold or if gold coated tungsten metal which is reducible by heat in the res is used, the ?ux may contain only gold, so ?lnce of the remaining constituents o the that the gold color may be maintained. If ux. ' 50 a platinum color be desired, palladium or 2. In the process of soldering or brazing platinum may be added, which also gives a oxidizable metals like tungsten or molybde 115 stronger bond and a joint of‘higher melting num, the step which consists in heating said point. In this manner pure platlnum may metal in contact with a ?ux containing an be used in extreme cases, although its use re oXid-dissolving and oxygen-excluding ele? 55 quires very delicate manipulation since with ment togethen, with a reducible precious temperatures much above 14000 C. there is metal salt. 120 danger of crystallization or annealing. Sil 3. The process of coating tungsten or ver alone may be employed (though with molybdenum or their alloys with a layer of slightly more difficulty in the reduction unoxidizable metal such as gold or silver since some reducing agent like potassium or alloys containing the same which consists cyanid is sometimes desirable as an added in first applying to the tungsten or molyb 125 constituent of the ?ux to aid its reduction)‘ denum a ?ux containing the oxygen salt of but adheres rather weakly and appears for an alkali metal together with other sub some unknown reason to accelerate crystalli stances which when heated will act to pre 1,236,388 till cipitate upon the tungsten or molybdenum ing said oxidizable metal in contactlwith an adherent coating of the unoxidizable an oxygen alkali salt to which is added the metal. halid salt or salts of the coating metal or 10 4:. The process of coating tungsten and metals desired. 5 molybdenum with silver, gold, palladium, In testimony whereof, I hereunto at?x my platinum or other noble metal,'either singly signature. ' or in alloyed form, which consists in heat- FRANK A. FAHRENWALD.