Claims
- 1. A method of forming a coating on a substrate with a plasma gun, comprising the steps of:
- providing a plasma gun and a substrate;
- operating the plasma gun to produce a plasma stream which flows from the plasma gun to the substrate, the step of operating including introducing a plasma gas into the plasma gun to establish plasma gas operating conditions;
- introducing coating material into the plasma stream within the plasma gun so that the coating material is carried by the plasma stream to the substrate to form a coating on the substrate;
- providing an ambient pressure outside of the plasma gun and an internal pressure within the plasma gun which is substantially larger than and forms a relatively large ratio with the ambient pressure; and
- providing the plasma gun with an exit configuration for the plasma stream through an opening which, for the plasma gas, plasma gas operating conditions and the ratio of the internal pressure with the ambient pressure, causes the plasma to undergo substantial expansion, with accompanying shock waves and turbulence, as the plasma stream exits the plasma gun, so that enough energy is contained in the plasma stream to provide a relatively uniform coating of the coating material on the substrate, over a region of the substrate many times wider than the width of the opening of the plasma gun.
- 2. A method in accordance with claim 1, wherein the step of providing a pressure differential comprises providing an ambient pressure of 10-0.001 Torr. outside of the plasma gun.
- 3. A method in accordance with claim 1, wherein the step of providing a pressure differential comprises providing a pressure inside the plasma gun of 1-100 atm.
- 4. A method in accordance with claim 1, wherein the step of introducing coating material comprises introducing powder particles no greater than 10 microns in size into the plasma stream within the plasma gun.
- 5. A method in accordance with claim 1, wherein the substrate comprises an elongated strip of material having a generally uniform width thereacross and the plasma stream extends across the width of the substrate at a fixed location, and comprising the further step of continuously advancing the elongated strip comprising the substrate through the fixed location.
- 6. A method in accordance with claim 1, wherein the plasma gun has an internal throat upstream of the opening and the step of providing the plasma gun with an exit configuration comprises, for a given cross-sectional area of the internal throat, providing the opening with a cross-sectional area which expands the plasma stream to a sufficient extent to create a substantial shock wave in the plasma stream as it exits the opening.
- 7. A method in accordance with claim 1, wherein the step of providing the plasma gun with an exit configuration comprises, for the plasma gas, plasma gas operating conditions and the ratio of the internal pressure with the ambient pressure, determining an ideal exit configuration of the plasma gun which provides relatively smooth, aerodynamic flow of the plasma stream from the plasma gun, and providing the plasma gun with an exit configuration substantially different from the given exit configuration to produce a plasma stream which undergoes substantial expansion, with accompanying shock waves and turbulence, as the plasma stream exits the plasma gun.
- 8. A method in accordance with claim 1, wherein the exit configuration is defined by the ratio of an area of an exit of the plasma gun to an area of a throat upstream of the exit.
- 9. A method of operating a plasma system comprising the steps of:
- operating a plasma gun to produce a plasma stream, the plasma gun having a flow path with an exit configuration from an internal throat through and opening downstream of the internal throat where the plasma stream exits the plasma gun;
- providing an ambient pressure of 10-0.001 Torr. outside of the plasma gun;
- providing an internal pressure within the plasma gun which is substantially greater than the ambient pressure outside of the plasma gun, to provide a relatively large ratio of internal pressure to ambient pressure;
- introducing a plasma gas into the plasma gun to establish plasma gas operating conditions; and
- for the ratio of internal pressure to ambient pressure, the plasma gas and the plasma gas operating conditions, determining an ideal exit configuration of the flow path which provides smooth, aerodynamic flow of the plasma stream from the plasma gun, and then providing the plasma gun with an exit configuration substantially different from the ideal exit configuration to produce a plasma stream which undergoes substantial expansion, with accompanying shock waves and turbulence, as the plasma stream exits the plasma gun.
- 10. A method in accordance with claim 9, wherein the plasma gun has a nozzle exit with a cross-sectional area forming an area ratio with a cross-sectional area of the internal throat, and the step of determining an ideal exit configuration comprises the steps of:
- for the ratio of internal pressure to ambient pressure, the plasma gas and the plasma gas operating conditions, determining an optimum area ratio of the cross-sectional area of the internal throat of the plasma gun to the cross-sectional area of the nozzle exit of the plasma gun which produces natural expansion of the plasma stream as it exits the nozzle exit; and
- having determined the optimum area ratio, configuring the flow path of the plasma gun to have an area ratio substantially less than the optimum area ratio.
- 11. A method in accordance with claim 9, wherein the step of providing an internal pressure within the plasma gun comprises providing an internal pressure of 1-100 atm.
- 12. A method in accordance with claim 9, comprising the further step of introducing powder particles no greater in size than approximately 10 microns into the plasma stream within the plasma gun.
- 13. A method in accordance with claim 9, wherein the substrate is provided in the form of an elongated strip of material having a generally uniform width thereacross, and comprising the further steps of positioning the substrate so that the plasma steam extends across the width of the substrate at a fixed location, and continuously advancing the substrate through the fixed location.
- 14. A method of operating a plasma system comprising the steps of:
- operating a plasma gun to produce a plasma stream, the plasma gun having a flow path with a given exit configuration having an opening through which the plasma stream exits the plasma gun;
- providing an internal pressure within the plasma gun which is substantially greater than the ambient pressure outside of the plasma gun, to provide a relatively large ratio of internal pressure to ambient pressure;
- introducing a plasma gas into the plasma gun to establish plasma gas operating conditions;
- for a given exit configuration, determining an ideal ratio of internal pressure to ambient pressure which provides relatively smooth, aerodynamic flow of the plasma stream from the plasma gun; and
- operating the plasma gun with a ratio of internal pressure to ambient pressure sufficiently different from the ideal ratio so that the plasma stream undergoes substantial expansion, with accompanying shock waves and turbulence, as the plasma stream exits the plasma gun.
- 15. A method in accordance with claim 14, wherein the given exit configuration is defined by the ratio of an area of the opening to an area of a throat upstream of the exit.
Parent Case Info
This is a continuation of application Ser. No. 08/667,116, filed on Jun. 19, 1996, now abandoned, which application is a division of Ser. No. 08/292,399, filed Aug. 18, 1994, U.S. Pat. No. 5,679,167.
US Referenced Citations (32)
Foreign Referenced Citations (1)
Number |
Date |
Country |
01252781 |
Oct 1989 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Muehlberger, U.S. Patent Reexamination Certificate B1 4,328,257, dated Sep. 1, 1987. |
Divisions (1)
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Number |
Date |
Country |
Parent |
292399 |
Aug 1994 |
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Continuations (1)
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Number |
Date |
Country |
Parent |
667116 |
Jun 1996 |
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