Method and apparatus for plasma flame-spraying coating material onto a substrate by means of passing a plasma-forming gas through a nozzle electrode, passing an arc-forming current between said nozzle electrode and a rear electrode to form a plasma effluent, introducing spray coating material into the plasma effluent, passing the plasma effluent axially through a wall shroud extending from the exit of said nozzle electrode and forming a hot gas shroud for the plasma effluent at least within the wall shroud.
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1. A plasma spray gun assembly for coating substrates comprising, in combination:
a nozzle electrode having a nozzle passage therethrough; a rear electrode; means for passing plasma-forming gas through the nozzle electrode; means for passing an arc-forming current between said electrodes to form a plasma effluent; means for introducing spray coating material into the plasma effluent; a wall shroud for said plasma effluent extending from the exit of the nozzle electrode; and means for forming a hot gas shroud for said plasma effluent at least within the wall shroud directed at an angle such that the gas has a component of flow extending in a direction opposite to the direction of flow of the plasma effluent.
2. A plasma spray gun assembly according to
3. A plasma spray gun assembly according to
4. A plasma spray gun assembly according to
5. A plasma spray gun assembly according to
6. A plasma spray gun assembly according to
7. A plasma spray gun assembly according to
8. A plasma spray gun assembly according to
9. A plasma spray gun assembly according to
10. A plasma spray gun assembly according to
11. A plasma spray gun assembly according to
12. A plasma spray gun assembly according to
13. A plasma spray gun assembly according to
14. A plasma spray gun assembly according to
15. A plasma spray gun assembly according to
16. A plasma spray gun assembly according to
17. A plasma spray gun assembly according to
18. A plasma spray gun assembly according to
19. A plasma spray gun assembly according to
20. A plasma spray gun assembly according to
direction of flow of said plasma effluent. 21. A plasma spray gun assembly according to claim 5 further comprising second jet orifice means directed at an angle of from about zero degrees to about 180° with respect to the axis of the plasma effluent. 22. A plasma spray gun assembly according to claim 5 further comprising second jet orifice means directed at an angle having a component extending parallel to the direction of flow of said plasma effluent. 23. A plasma spray gun assembly according to claim 5 further comprising second jet orifice means directed at an angle having a component extending in a direction opposite to the direction of flow of said plasma effluent. 24. A plasma spray gun assembly according to claim 1 wherein said wall shroud has a radially-inwardly directed lip portion disposed towards the exit end thereof. 25. A process for plasma flame-spraying coating material onto a substrate, which comprises the steps of: passing a plasma-forming gas through a nozzle electrode; passing an arc-forming current between said nozzle electrode and a rear electrode to form a plasma effluent; introducing coating material into the plasma effluent; passing the plasma effluent longitudinally through a wall shroud extending from the exit of said nozzle electrode; and forming a hot gas shroud for said plasma effluent at least within the wall shroud directed at an angle such that the gas has a component of flow extending in a direction opposite to the direction of flow of the plasma effluent. 26. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said coating material is in a powder form. 27. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said hot gas shroud is directed at an angle of between about 160° to about 180° with respect to the axis of the plasma effluent. 28. A process for plasma flame-spraying coating material onto a substrate according to claim 27 wherein said hot gas shroud is directed at an angle of about 180° with respect to the axis of the plasma flame. 29. A process for plasma flame-spraying coating material onto a substrate according to claim 25 further comprising the step of passing cooling water through said wall shroud. 30. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said coating material is introduced into the plasma effluent adjacent the exit of the electrode nozzle. 31. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said step of forming a hot gas shroud for said plasma effluent at least within the wall shroud includes the step of passing the gas for forming said hot gas shroud through an electric preheater. 32. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said step of forming a hot gas shroud for said plasma effluent at least within the wall shroud includes the step of using a second plasma flame gun assembly for preheating the gas for said hot gas shroud. 33. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said step of forming a hot gas shroud for said plasma effluent at least within the wall shroud includes the step of passing the gas for said hot gas shroud through an internal passageway of generally serpentine configuration in said wall shroud. 34. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said step of forming a hot gas shroud for said plasma effluent at least within the wall shroud includes the step of preheating the gas for said gas shroud to a temperature above about 300°C 35. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said step of forming a hot gas shroud for said plasma effluent at least within the wall shroud includes the step of preheating the gas for said gas shroud to a temperature of between about 500°C and about 1000°C 36. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein the gas for said hot gas shroud is a reducing gas. 37. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein the gas in said hot gas shroud is in a turbulent state. 38. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein the gas for said hot gas shroud is an inert gas. 39. A process for plasma flame-spraying coating material onto a substrate according to claim 38 wherein said inert gas is selected from the group consisting of nitrogen, argon and helium. 40. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein the gas for forming said hot gas shroud includes a combustible gas. 41. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein the flow rate of said gas in said hot gas shroud is above about 500 cubic feet per hour. 42. A process for plasma flame-spraying coating material onto a substrate according to claim 41 wherein the flow rate of the gas for forming said hot gas shroud is between about 1000 cubic feet per hour and about 2000 cubic feet per hour at a temperature of about 500°C 43. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said coating material is a fusible powdered metal. 44. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said coating material is a ceramic material. 45. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein said coating material is a carbide. 46. A process for plasma flame-spraying coating material onto a substrate according to claim 25 further comprising the step of forming a fluid annular curtain around the plasma effluent as it leaves the wall shroud passing towards said substrate. 47. A process for plasma flame-spraying coating material onto a substrate according to
48. A process for plasma flame-spraying coating material onto a substrate according to
effluent. 49. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein a portion of the gas for forming said hot gas shroud is introduced at an angle of about 180° with respect to the axis of the plasma effluent and a second portion of the gas for forming said hot gas shroud is introduced at an angle of from about zero degrees to about 180° with respect to the axis of the plasma effluent. 50. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein a portion of the gas for forming said hot gas shroud is introduced at an angle of about 180° with respect to the axis of the plasma effluent and a second portion of the gas for forming said hot gas shroud is introduced at an angle having a component extending parallel to the direction of flow of said plasma effluent. 51. A process for plasma flame-spraying coating material onto a substrate according to claim 25 wherein a portion of the gas for forming said hot gas shroud is introduced at an angle of about 180° with respect to the axis of the plasma effluent and a second portion of the gas for forming said hot gas shroud is introduced at an angle having a component extending in a direction opposite to the direction of flow of said plasma effluent. |
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This Application is a Reissue Application of Pat. No. 4,121,082, issued Oct. 17, 1978. 99. FIG. 5 shows in schematic form an annular wall shroud 80 with plasma flame or effluent 82 passing longitudinally therethrough along an axis indicated at 84. In this embodiment, an annular hot gas shroud 86 is directed parallel to the direction of flow of the plasma effluent.
In the embodiment of FIG. 6, the plasma effluent 82 passes longitudinally along its axis 84 through an annular wall shroud 88, and an annular hot gas shroud 90 is directed at an angle having a component extending parallel to the direction of flow of the plasma effluent. 7.
Referring next to the embodiment of FIG. 7 5, the plasma effluent 82 passes longitudinally along its axis 84 through an annularly-shaped wall shroud 92, and a portion of the gas for forming the hot gas shroud is introduced, as indicated at 94, at an angle of about 180° with respect to the axis 84 of the plasma effluent, and a second portion of the gas for forming the hot gas shroud is introduced, as indicated at 96, at an angle having a component extending parallel to the direction of flow of the plasma effluent.
In the embodiment of FIG. 8 6, the plasma effluent 82 passes longitudinally along its axis 84 through an annular wall shroud 98, and an annular hot gas shroud 100 is directed at an angle having a component extending in a direction opposite to the direction of flow of said plasma effluent.
FIG. 9 7 shows an embodiment of the invention wherein the plasma effluent 82 passes longitudinally along the axis 84 through an annular wall shroud 102. A portion of the gas for forming the hot gas shroud is introduced, as indicated at 104, at an angle of about 180° with respect to the axis 84 of the plasma effluent and a second portion of the gas for forming said hot gas shroud is introduced, as indicated at 106, at an angle having a component extending in a direction opposite to the direction of flow of the plasma effluent.
It will be appreciated that the characteristics of the hot gas as set forth in detail in connection with the embodiment of FIG. 1 are applicable to the embodiments of FIGS. 4 to 9 7.
Thus, it will be appreciated that the gas for forming the hot gas shroud may be introduced at one or more inlets and each inlet may be disposed at any angle from about zero to about 180° , and may even be normal to the direction of flow of the plasma effluent.
In order to more fully illustrate the nature of the invention, FIG. 10 8 presents a table indicating the comparative test results, spraying the same material, of a conventional plasma spray gun assembly without shrouding and a plasma spray gun assembly constructed according to the invention. The test results show a clear superiority of the spray gun assembly of the present invention.
It will thus be seen that the present invention does indeed provide a new and improved plasma spray gun assembly which is superior to conventional spray guns with respect to deposition efficiency, reduced oxide contents, reduced unmelted particle inclusions, as well as other operative characteristics.
Having thus described the invention with particular reference to the preferred forms thereof, it will be obvious to those skilled in the art to which the invention pertains, after understanding the invention that various changes and modifications may be made therein without departing from the spirit and scope of the invention, as defined by the claims appended hereto.
Harrington, John H., Smyth, Richard T., Weir, John D.
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Nov 13 1980 | Metco Inc. | (assignment on the face of the patent) | / | |||
| Mar 10 1986 | METCO INC , A CORP OF DE | PERKIN-ELMER CORPORATION, THE | ASSIGNMENT OF ASSIGNORS INTEREST | 004526 | /0539 | |
| Jul 02 1996 | PERKIN-ELMER CORPORATION, THE | SULZER METCO US , INC | MERGER SEE DOCUMENT FOR DETAILS | 008126 | /0066 |
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