US1971804A - Method and apparatus for spraying powdered material - Google Patents

Description

Aug. 28,. 1934. P. P. ALEXANDER METHOD AND APPARATUS FOR SPRAYING POWDERD MATERIAL Filed Deo. 4, 1929 Am m ol ,t

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155 saphir@ Y Patented Aug. 28, 19.34

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. minion AND APPARATUS FOB SPRAYING POWDEEED MATERIAL Peter P. Alexander, Marblehead, Mass., assignor to General Electric Company, a corporation of- New York Application December 4,' 1929, Serlal No. 411,694 'l Claims. (Cl. 91-70.1)

The present invention relates to an apparatus and method for spraying powdered material and more particularly hard metal compositions of the character described in Schrter Patents Nos.

5 1,549,615 and 1,721,416 onto a supporting or foundation metal body. The product disclosed in these patents consists generally of a carbide of an element of the 6th group of MendelejefPs periodic table, such as tungsten carbide, and an auxiliary l binder or cementing metal of the iron group, such as cobalt. 'lhesematerials are usually mixed together in powdered form, pressed into a desired shape under high pressure and then heated to the sintering temperature of the mixture which may .l be in the neighborhood of 1380 C. but will vary according to the composition employed. The iinished product is usually brazed or vwelded to a supporting member and thereafter commonly employed as a metal cutting tool or die.

According to the present invention, powdered hard metal compositions of the character disclosed in the above Schrter patents are superheated and sprayed directly onto a supporting metal member thereby providing a uniform layer of hard metal which is suitable for use either as a wear resisting surface or as a metal cutting tool.

In spraying materials of this character, it is desirable to prevent oxidation of the sprayed material as otherwise its physical properties are adversely affected. It is also necessary to control 'l carefully the temperature to which the powdered materials are heated. I have found that the temperature employed should be high enough to cause melting of the binder element, i. e. cobalt. It

- should not however be high enough to melt the tungsten carbide since melting will alter considerably its physical properties.

The novel features which are characteristic of my invention are set forth with particularly in the appended claims. 'I'he invention itself how-- 45 of a spray device whereby my invention may be carried into eiect, while Fig. 2 is a cross section oi a modiiled form of spray torch.

Referring more particularly to the drawing, I have indicated at 1 an outer metal casing-or envelope spaced from an inner receptacle 2. Mounted within the latter is a heating chamber 3 spaced from the container 2 by a suitable insulating material 2' such as magnesium omda. v'.llhe heating ber 3 consists'of a cup-shaped x e and a concentrically s .r

hollow graphite member 5 provided with a plurality of inclined openings 8. The member 5 surrounds an opening 6 in Ithe bottom of the cup-I shaped member 4 and extends a short distance above the'upper end of the cup-.shaped member. 60 The side and bottom walls of member 4 are provided with a plurality of ducts '7 which communicate with the opening o and with the member 5.

A graphiteor tungsten pipe 9 is concentrically disposed within the member 5 and extends 65 through and beyond the latter member and envelope 1. The pipe 9 has a relatively large opening 10 adjacent the upper end of and within the member 5 providing an outlet throught-.he pipe for the' hot gas which ows through the heat- 70 ing chamber 3. A pair of insulating closure plugs 11 and 12 are tted in the upper ends of members 4 and 5 respectively, while a graphite plug 13, tted around the pipe 9, acts as a closure member for the opening 6, the plug being mounted in that portion of opening 6 below the ducts 7.

The graphite member 5 and the central pipe 9 are provided with electrically conducting collars 14 and 15 respectively, adapted to be connected to a suitable source of electrical energy throughso leads 16 and 17 which extend through insulating collars 18 mounted on the upper end of envelope i.

In operation, a nely divided mixture of tungsten carbidel and cobalt in suitable proportions is fed into the upper end of pipe 9. A nonoxidizing gas such as carburetted hydrogen, pure nitrogen, pure argon, or nitrogen with a small percentage of hydrogen is supplied to the envelope 1 through a pipe 19. One portion of the gas flows downwardly in the space between envelope 1 and container 2 and then outwardly through a series of openings -20 in the bottomof container 1 andadjacent the pipe 9. The remainder ofthe gas supplied to the envelope ows downwardly through the ducts '7 into the opening 6 and around the inner graphite member 5 and iinally through opening 10 into the pipe 9.

An electric current flows through the pipe 9 and graphite member 5 and heats these portions of the device to a temperature up to about 3000 C. At this temperature hydrogen reactswith graphite, forming hydrocarbons such as CHi, C2H2 eta-so that even if hydrogen is employed the gas entering the tube y9 through the opening 10 is not purey hydrogen vbut contains,a considerable percentage of hydrocarbons'. Thev gases therefore which come in contact with the powdered in tube 9 are not only nonom but non-deca: f. as well.

. emerge as a jet or spray from the lower end ofn f the pipe, the spray being surrounded by afshield of non-'oxidizing gas from the openings, 20. lThe e foundation metal or body 21 to be coated may be mounted on a movablertable 22 adjacent the lower end of pipe A9.r As the iet strikes body y21 it has a temperature above the melting point of cobalt and iron, i. e. about 2200*? C. and forms a thin layer yof semi-plastic material which adheres to the supporting body 21. f y While the electric current kflowing through the members t and 5 and ypipe 9 heats the powdered materials to the desired elevated temperature, .an additional source of heat, ksuch 'as a tungsten or graphiter radiant heater, maybe employed if i ldesired to heat the body 21. kAn arrangement of vintol the pipe 26.

refractory .cement made by mixing rzirconium f oxide with sodium silicate and magnesium oxide is plastered von; to the graphiteheater 23. After, drying, this insulating coating prevents excessiveoxidation ofthe heater23 and `also limits thek 'loss offheat intothe surrounding atmosphere.y

this character' isdisclosed in Fig. 2 of the drawing, in'which aA hollow graphite heater 23 is prol vided at itsiupper end witha cap- 24 andlat its lower end with a screw-'threaded graphite plug 25 which. acts as Aa. radiant heater.

' Atungsten or graphite tube 26 extends centrally through the heater 2,3 and p1ug25 and is insulated from cap 24 by ya collar 2'7.: Tube 28- is provided with an opening 28' within the 'member 23 to permit the'ow of gas from heater 24 A coating 29 of insulating A split graphite collar 30 surrounds the heater 23 kandis connected to a wire 31. A similar wire 32 Vis connectedto a vconducting collar 33 mounted on tube 126. When wires 31'and {i2-'are connected to a suitable source of electrical energy, current ows through the heater 23,` plug'25` and tube 26 heating them to the desired temperature.

In operation, a powdered mixture such as described in connection with Fig. 1 is supplied to the tube 26, while a gas such as hydrogen, nitrogen, argon or the like ows through pipe 34 connected to the heater 23 and to a suitable source of gas supply. The gas ows through the heater 23 and opening 28 into the tube 26 and diffuses through the powdered materialv in the tube. V'I'he electric current owing through the heater 23 -and tube 26 heats the powdered materials and gas and plug 25 to an elevated temperature. Plug 25 acting as Ka radiant heater provides a supplemental source of heat for the body 21 and the material deposited thereon.

The gas introduced into heater 23 provides a non-oxidizing and non-decarbonizing atmosphere for the deposition of the powdered materials on the body 21. The deposited material forms a semi-plastic layer on the supporting body 2l', and when cooled is suitable for use as a wear resistant surface or metal cutting tool. What I claim as new and desire to secure by Letters Patent of the United States, is:

1. 'I'he method of applying to a foundation metal a coating consisting mainly of a metal of the 8th group of Mendelejefis periodic table but f containing appreciable but minor quantities of e y carbon and metal of the iron group, which comprises mixing the materials which comprise said coating in finely dlvidedfform, heating them to a' relatively high temperature but below the melting point ofthe carbide of said metal or the 6th group, applying said mixture in the form of a spray and in a non-oxidizing andl non-decarbonizing atmosphere to said foundation metal.

2. The method of applying torafoundation body a coating which consists mainly of tungsten but bon andk metal of the iron group, which comprises mixing the materials which comprise said coating, heating them to a temperature below tionl body in the form of a spray and in a nonoxidizing and vnon-deearbonizing atmosphere.

3.` The method of applying a coating consisting y -of tungsten carbide and cobalt tok a foundation metal whichcomprises mixing powdered tungsten carbide 'and cobalt introducing said mixture into a vcontains appreciable but minor quantities of cary stream of non-oxidizing and non-decarbonizing gas, heating said gas and powdered `mixture to a temperature of about .2200" Cpand applying said mixture to a foundation metal.

4. The method oi?` applying a coating consisting of'tungsten carbide and cobalt toa foundation f metal which comprises mixing powdered tungsten carbide and cobalt introducing said mixture into a stream of non-oxidizing gas, heating said gas and powdered mixture to a temperature Lof about 2200 C.'and applying said mixture to a foundation metal.

extending through and spaced from said member,

to an elevatedl temperature, means for circulating a.4 gas through said hollow member and pipe and means whereby powdered materials may be supplied to said pipe.

6. The method of applying to a foundation body a coating consisting mainly of a hard metal carbide but containing an appreciable quantity of metal having a lower melting point than said carbide, which comprises mixing said carbide and metal in a ilnely divided condition, heating the mixture to a relatively high temperature but below the melting point of said carbide and applying said heated mixture to said foundation body in the form of a spray, said spray being surrounded by a shield of non-oxidizing gas.

fl. A spray device comprisinga hollow member of refractory material, an insulated pipe of refractory material extending through and spaced from said member, means whereby a non-oxidizing gas and powdered material may be supplied under pressure to saidpipe, and means for passing an electric current through said pipe and member to thereby heat the material within said pipe to an elevated temperature. l

PETER P. ALEXANDER.

l means for heating said hollow member and pipe f

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