US3246114A - Process for plasma flame formation - Google Patents

Description

Aprifl 12 16 L. MATVAY PROCESS FOR PLASMA FLAME FORMATION Original Filed Dec. 14, 1959 MUNDOM Nmz fl m&

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PROCESS FGR PLASMA FLAME FORMATION LeoMatvay, 603 San Juan Drive, 7, Sunnyvale, Calif. Application Feb. 7, 1962, Ser. No. 174,344, new Patent No. 3,179,782, dated Apr. 20, 1965,-which is a continuation of abandoned application Ser. No. 859,292, Dec.

14, 1959. Divided and this application Feb. 9, 1965,

Ser. No. 431,27

The portion of the term of the patent subsequent to Apr. 21, 1982, has been disclaimed 2 Claims. (Cl. 21976) This invention relates to plasma flame apparatus and more particularly to a plasma flame jet spray gun with an enclosed arc region that is also a controlled arc region fo r reeciving at controlled amounts and pressures working gas to be turned into plasma and at controlled amounts work matter that isto be heated to a very high temperature to be sprayed as particles to form a high density deposit upon the base material.

This application is a division of my prior copending application Serial Number 174,344, filed February 7, 1962, now Patent No. 3,179,782, which was a continuation of my prior copending application, Serial Number 859,292, filed December 14, 1959, now abandoned.

'It is an object .of the present invention to provide a high-temperature .or hyperthermal plasma flame apparatus wherein the-work matter, in any suitable form, is introduced into the arc in a controlled arc region and at, or just prior to the point at which the working gas is ionized by the arc.

Another object of the present invention is to provide a plasma flame device Where all of the work matter goes directly into the controlled arc region and all of the work matter is turned into molten, gaseous vapor or atomic particles, hereinafter called particles, and further all of the. particles .go directly out the orifice to be deposited upon the base-material.

.gStill a further object of the present invention is to provide aplasma flame device which deposits a uniform high. density deposit having good adhesion, cohesion, bonding, sealing, plating or cladding qualities.

Still another object of the present invention is to provide a plasma flame device that prevents globs of cooled work matter from building up inside the plasma flame jet spray gun and causing clogging, spattering and sputtering.

. Still a further object of the present invention is to provide a plasma flame device that beats the work matter uniformly throughout to predetermined temperatures overa wide range, from a few hundred to thirty thousand or more degreesFahrenheit.

, Still another object of the present invention is to provide a plasma flame device where both electrodes are effectively and sufliciently cooled to make it possible to operate the device on D.C.S.P., D.C.R.P. or AC.

Still a further object of the present invention is to provide aplasma flame device where the electrodes have a large cross section area to carry a high electrical current.

Still another object of the present invention is to provide a plasma flame device capable of propelling the particles at supersonic velocity to impinge them into or upon the base material.

Still a further object of the present invention is to provide a plasma flame jet spray gun which can be produced, packaged, and sold in large quantities at a comparatively low cost, and which can be conveniently utilized wherever needed.

Still additional objects, benefits, and advantages of this invention will become evident from a study of the following detailed description taken in conjunction with the accompanying drawing, in which:

United States Patent 0 FIGURE 1 is a partly schematic, sectional view taken along the axial centerline of plasma flame apparatus embodying a preferred form of this invention.

FIGURE 2 is a cross section view taken along line 2-2 of FIGURE 1 showing interior arrangement of the coolant flow in the semiannular cavities between the draw screw and electrode chuck.

Referring now specifically to the drawing, a plasma flame jet spray gun 10 made in accordance with the present invention preferably comprises a hollow cylindrical plastic body 12 into which draw screw 13 is inserted.

The draw screw 13 is held firmly in place and axially aligned in the plastic body 12 by the draw nut 14.

Two O-ring seals 15, preferably of silicone rubber, are disposed in suitable grooves in draw screw 13 for purposes to be hereinafter more fully explained. Next the electrode chuck 16 is inserted into the draw screw 13 forming upper and lower serm'annular cavities 17 and 18, respectively.

Adjustment nut 19 is attached to the electrode chuck 16 by the idler screw 20. As the adjustment nut 19 is screwed along its mating threads on the draw screw 13 the electrode chuck 16 is forced in or out along the axial centerline of the plasma flame jet spray gun 10.

Plastic cover 21 is press fitted over the adjustment nut 19.

The rod electrode 22 is supported in axial alignment as by a pipe thread which engages a mating self sealing taper pipe thread in the electrode chuck 16.

The hollow cylindrical outer jacket 23 is slipped over the hollow cylindrical arc chamber jacket 24 and they are respectively axially aligned to eachother by the inward flange of the outer jacket 23 and the outward flange of the arc chamber jacket 24, thus forming the annular coolant cavity 25.

Two silicone rubber seals, O- rings 26 and 27 are located in suitable grooves in the outer jacket 23 and are chamber jacket 24, respectively. Then the outer jacket 23 and the arc chamber jacket 24 are attached as a unit, to the plastic body 12 by anchor screws 28. Screws extend through the plastic body 12 into threaded mating holes in the outer jacket inward flange.

Next the hollow cylindrical electrical insulator 29, having radial holes 30, is inserted into the arc chamber jacket 24 in axial alignment to form an annular gas cavity 31.

Two silicone rubber seals, O-rings 32 and 33, are located in suitable grooves in the outer orifice 34. The smaller O-ring 32 forms a seal between outer orifice 34 and the inside surface of the arc chamber jacket 24 and larger O-ring 33 forms a seal between outer orifice 34 and the inside surface of the outer jacket 23 thereby extending the length of the annular coolant cavity 25 into the outer orifice 34.

The outer orifice 34 is held in place by half head screws 35.

The washer electrode 36 is inserted into the outer orifice 34 to butt up against the electrical insulator 29 and is held firmly in place in axial alignment with the rod electrode 22 by screwing the inner orifice 37 into a mating threaded hole in the outer orifice 34.

The Pitot tubes 38, one shown, are located to deliver work matter 54 to the critical point in the controlled arc region 52.

Rubber seal, 'O-ring 39a, is located in a suitable groove in the adapter nipple 40. The adapter nipple 40 is screwed into a threaded mating hole in the outer jacket 23 to act as both the coolant inlet 41 and electrical conductor 42 connection terminal for supplying electrical current to the washer electrode 36.

Rubber seal, O-ring 39, is located in a suitable groove in the adapter nipple 43. The adapter nipple 43 has a central bore providing a passageway therethrough and is disposed in a suitable aperture in draw screw 13 with its bore in communication with lower cavity 18. The adapter nipple 43 acts as both the coolant outlet 44 and electrical conductor 45 connection terminal for supplying electrical current to the rod electrode 22.

Rubber seal, O-ring 39', is located in a suitable groove in the plastic adapter nipple 46. The plastic adapter nipple 46 is then screwed into a threaded mating hole in the plastic body 12. The plastic adapter nipple 46 has a central bore which comprises the working gas inlet 47. a

Three rubber seals, O-rings 39", are located in suitable respective grooves in the hollow cylindrical coolant passage 48. The hollow cylindrical coolant passage 48 has a passageway therethrough and is disposed in a suitable aperture in draw screw 13 with its passageway in communication with upper cavity 17.

The operation of this device will now be readily understood. Under controlled pressure, gases, such as argon, helium, hydrogen, nitrogen or other gases, hereinafter called working gas 49, enter the plasma flame jet spray gun 10 at working gas inlet 47 The working gas 49 flows through the plastic adapter nipple-46into the annular gas cavity 31. The Working gas 49 circulates in the annular gas cavity 31 acting as both a coolant and thermal barrier to the surfaces of the plastic body 12, draw screw 13, and electrical insulator 29.

The working gas 49 leaves the annular gas cavity 31 through the radial holes 30 and passes into the inner annular gas cavity 50. The working gas 49 circulates in the inner annular gas cavity 50 acting as both a coolant and thermal barrier to the surfaces of the draw screw 13, electrode chuck 16, and electrical insulator 29.

The working gas 49 flows through the arc chamber 51 into and through the controlled arc region 52. As the working gas 49 passes through the controlled arc region 52, the space between the rod electrode 22 and the washer electrode 36, the electrical energy is transformed into heat and a portion of the Working gas 49 becomes ionized and the working gas becomes a plasma flame 53.

Also at this point, the controlled arc region 52, at the same instant or a fraction of a second before the portion of the working gas 49 becomes ionized, a controlled amount of work matter 54 in any desired suitable form is introduced into the controlled arc region 52 through the Pitot tubes 38.

Under the controlled arc region arrangement all of the work matter 54 enters directly into the controlled arc region 52, the same instant the working gas 49 becomes ionized and the Work matter 54 is immediately heated to a temperature as high as 30,000 F. At this high temperature the work matter 54 may be changed to molten, gaseous vapor or atomic particles indicated generally at 55. While in the controlled arc region 52, the heating of all work matter 54 to particles 55 is uniform throughout.

From this point in the controlled arc region 52 all of the particles 55 are turned directly out through tthe orifice 56 by the plasma flame '53 and conveyed to the base material 57 at sonic or supersonic velocity and form a high density deposit 58 by adhesion, cohesion, bonding, plat- .ing or cladding.

The controlled arc region arrangement was arrived at after a number of tests and experiments. Examples of two of the most informative tests and experiments follow:

Example 1 First it was attempted to introduce the work matter 54 into the plasma flame 53 outside the plasma flame jet \very poorly deposited, upon the base material 57.

In another attempt the Work matter 54 was mixed with the Working gas 49; the work matter 54 being tangentially swirled in the arc chamber 51. This resulted in good particle 55 spraying of a deposit 58 upon the base material 57. But here again only random work matter 54, particles 55 would be carried out the orifice 56 and the rest of the work matter 54 would be heated inside the arc chamber 51 forming globs that would cause the gun to spatter and sputter and clog at the orifice 56.

In apparatus embodying this invention the work matter 54, whether it be metal or non-metal, is introduced neutral into the controlled arc region 52 at the same instant as the neutral working gas 49 is becoming electrically charged plasma flame 53. Thus all are exposed to the thermionic bombardment together While still in their neutral states of matter.

The working gas 49 is heated to a very high temperature and part of it becomes a plasma flame 53 and the work matter 54 is heated to a very high temperature and becomes particles 55. The temperature to which the working gas 49, plasma flame 53 and the work matter 54, particles 55 are raised is dependent upon a number of physical, chemical and electrical factors.

The physical factors are such things asthe space or gap between the rod electrode 22 and the washer electrode 36 which determine the electrical arc jump distance and, therefore, the impedance. The size'of the hole in the washer electrode 36 controls the amount of constriction upon the flow of working gas 49. The smaller the hole diameter in the washer electrode 36 the more the flow of working gas 49 is constricted and the more the concentration of heat and electrical energy is increased.

The chemical factors include, inter alia, the nature of the atomic or molecular structure of the work matter 54 and working gas 49; whether or not a catalytic action or chemical reaction occurs and, if so, whether itis endothermic or exotherimc, whether the work matter is metallic or non-metallic; and whether the work matter is magnetic, electrically charged or neutral. These chemical and physical chemical factors in themselves determine whether the plasma flame jet spray gun 10 will'develop temperatures of only a few hundred degrees or temperatures as high as thirty thousand degrees Fahrenheit or even higher.

The electrical factors are such things as the amount of current used andwhether the electrical current used is D.C.S.P., D.C.R.P. or A.C. I

When a D.C.S.P. circuit is used the. electron flow, kinetic energy, is from the negatively charged electrode to the positively charged electrode and the negatively charged electrode will remain relatively cool in comparison to the hot positively charged electrode. Therefore in a D.C.S.P. circuit the positively charged electrode requires cooling in some manner. However, when a D.C.R.P. or A.C. circuit is used both electrodes must be effectively and sufficiently cooled to keep them from melting and spattering because of the high temperature concentration upon their surface and within them.

The coolant 59 as a liquid or gas enters the plasma flame jet spray gun 10 at the coolant inlet41 and flows through the adapter nipple 40 into the annular coolant cavity 25, cooling and carrying heat away from the washer electrode 36, inner orifice 37, outer orifice 34 and arc chamber jacket 24.

The coolant 59 then flows from the annular coolant cavity 25 through the coolant passage 60 in the plastic body 12 down the hollow cylindrical coolant passage 48 into the upper cavity 17 in the draw screw 13.

As best seen in FIGURE 2, the coolant 59 cannot pass around the electrode chuck 16 because of the semiannular cavity construction, upper cavity 17 and lower cavity 18, in the draw screw 13. Rather the coolant 59 flows from the upper cavity 17 into the electrode chuck coolant passage 61 where the coolant 59 comes directly in contact with the rod electrode 22 to cool and carry heat away from it. Then the coolant 59 flows out through the electrode chuck coolant passage 62 to the lower cavity 18 and then out through the adapter nipple 43 to the coolant outlet 44.

The electric current is supplied to the plasma flame jet spray gun by way of the electric conductors 42 and 45. The power source 63 may be an electric arc welder generator or transformer.

The are region is enclosed and controlled so that the working gas is introduced therein at controlled pressures and volumes and the work matter, as a gas, liquid, slurry, powder or wire, is introduced into the controlled are region, through the Pitot tubes, at the instant, or fraction of a second before, a portion of the working gas becomes ionized thereby ensuring the proper heating and dispersal of the work matter.

Additionally, both electrodes are effectively and sufiiciently cooled so that it is possible to operate the plasma flame jet spray gun, embodying this invention, on D.C.S.P., D.C.R.P. or AC. and are preferably of relatively large cross sectional area so that a high electric current may be used in the gun.

The working gas circulating in the annular cavities 31 and within the arc chamber 51 adjacent the interior wall of the insulator 29 acts as both a coolant and a thermal barrier for the surfaces and chamber exposed to its circulation effect.

The electrode chuck 16 has a positive flow cooling system running through it which is controlled by simply rotating the chuck within the draw screw 13 so as to constantly, effectively and sufficiently cool and carry heat away from the electrode chuck and from the rod electrode 22.

The washer electrode 36 is easily and quickly changed or replaced without requiring removal of the outer orifice 34, by merely screwing the inner orifice 37 out of the outer orifice, thereby avoiding disturbing the O-ring coolant seals.

Rod electrode 22 is easily and quickly changed or replaced by merely unscrewing and replacing it. A selfsealing taper pipe thread is preferably used for rod electrode 22 so as to eliminate the need of gaskets and other materials which lose their effectiveness at high temperatures.

Because the adjustment nut 19 is supported on the idler screw 20, the electrode chuck does not turn as it is adjusted longitudinally by turning the nut 19.

With a plasma gun embodying this invention the base material need not be heated above its temper or heat treatment critical temperature to obtain good adhesion, cohesion, bonding, sealing, plating or cladding qualities.

The work matter may, for example, comprise such materials as aluminum, aluminum oxide, ammonia, beryllium, beryllium oxide, boron carbide, calcium zirconate, chromium, chromium boride, hydrocarbons, magnesium oxide,

molybdenum, nickel, niobium carbide, propane, Pyrex, stainless steel, Stellite 1, tantalum carbide, thorium, thorium oxide, titanium carbide, tungsten, tungsten carbide, uranium oxide, zinc, zirconium boride, zirconium carbide, zirconium oxide and others.

The particles of work matter are propelled or conveyed at sonic or supersonic velocity to the base material, impinging thereon to form a high density deposit.

The structure and shape of the arc chamber 51 and the disposition of rod electrode 22 therein is such that the surface material is not blown off the rod electrode. This is because the working gas flow is controlled by the internal configuration of the arc chamber and electrode chuck so that the working gas merely flows gently over the rod electrode.

Thermionic bombardment may proceed in either direction between the electrodes.

All oppositely charged electric current carrying parts are so assembled in the plasma fiame jet spray gun that they are at all times further apart from each other than the electrodes are from each other, when the gun is in operation.

The draw screw, outer orifice, inner orifice and are chamber jacket are preferably made from copper or other high thermal conductive material so that heat transfer is always from a part having a smaller relative rate of thermal conductivity to a part having a larger relative rate of thermal conductivity thus providing good cooling throughout the unit with no undesirable temperature build-up or thermal barriers arising between different parts in a direction outwardly from chamber 51.

While this invention has been described with particular reference to the construction shown in the drawing it shall be understood that changes may be made thereto within the spirit and scope of the present invention, which is defined by the appended claims.

I claim:

1. A process for coating a surface with a predetermined material comprising the steps of creating an electric are between axially spaced electrodes and across a chamber having an outlet orifice in axial alignment with said are, introducing a working gas capable of ionic disassociation into said chamber rearwardly of said electrodes remote from said orifice, ionizing said working gas in a controlled, enclosed arc region in said chamber adjacent said orifice to form plasma and simultaneously introducing coating material into said are region whereby to heat said coating material to a high temperature, and projecting said plasma and coating material through said orifice and onto said surface.

2. In a process for plasma jet spraying the step of ionizing a portion of a stream of working gas capable of ionic disassociation at a predetermined location in the flow of said gas and substantially simultaneously and no later introducing the matter to be sprayed into said stream of working gas at said location, without prior mixing of said working gas and matter to be sprayed.

References Cited by the Examiner UNITED STATES PATENTS 2,973,426 2/1961 Casey 219- 3,010,009 11/1961 Ducati 21976 3,016,447 1/1962 Gage et a1 219-76 3,075,066 1/1963 Yenni et al. 21976 RICHARD M. WOOD, Primary Examiner.

ANTHONY BARTIS, Examiner.

Claims (1)

1. A PROCESS FOR COATING A SURFACE WITH A PREDETERMINED MATERIAL COMPRISING THE STEPS OF CREATING AN ELECTRIC ARC BETWEEN AXIALLY SPACED ELECTRODES AND ACROSS A CHAMBER HAVING AN OUTLET ORIFICE IN AXIAL ALIGNMENT WITH SAID ARC, INTRODUCING A WORKING GAS CAPABLE OF IONIC DISASSOCIATION INTO SAID CHAMBER REARWARDLY OF SAID ELECTRODES REMOTE FROM SAID ORIFICE, IONIZING SAID WORKING GAS IN A CONTROLLED, ENCLOSED ARC REGION IN SAID CHAMBER ADJACENT SAID ORIFICE TO FORM PLASMA AND SIMULTANEOUSLY INTRODUCING COATING MATERIAL INTO SAID ARC REGION WHEREBY TO HEAT SAID COATING MATERIAL TO A HIGH TEMPERATURE, AND PROJECTING SAID PLASMA AND COATING MATERIAL THROUGH SAID ORIFICE AND ONTO SAID SURFACE.

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