Claims
- 1. In a method of operating a plasma-arc torch having a cylindrical casing and having a first, electrically conductive end wall including an extended length nozzle bore defining an anode nozzle passage extending axially therethrough and forming an anode electrode and a second, opposite end wall, a cathode electrode mounted coaxially within the opposite end wall of the cylindrical casing and being electrically insulated from the first end wall and terminating short thereof, said anode nozzle passage at its end facing said cathode electrode flaring outwardly and being conically enlarged, said method comprising the steps of:
- introducing a plasma producing gas under pressure into said chamber and creating an electrical potential difference between the cathode electrode and said anode nozzle to create a plasma-arc flame normally exiting from said anode nozzle passage, the improvement comprising;
- causing an arc of sufficient size at a point along the extended length nozzle bore sufficiently upstream of said nozzle exit orifice and to pass to the anode nozzle passage wall and to thereby establish an arc column which, with a downstream ionized region, is maintained wholly within the extended length nozzle bore, thereby extending the life of the circumferential anode region in the vicinity of the exit of the anode nozzle, while yielding full control over the arc-length characteristics, and
- introducing particles to be sprayed at a point within said plasma-arc flame downstream of said arc column with its downstream ionized region at an area of said plasma-arc flame in the form of a high velocity hot gas stream exhibiting no ionization with said particles accelerated to extreme velocity for impact against a workpiece surface to be coated, thereby eliminating excessive heating of the particles prior to impact.
Parent Case Info
This application is a continuation of application Ser. No. 07/193,702 filed May 13,1988, now U.S. Pat. No. 4,841,114, to applicant and entitled "HIGH-VELOCITY CONTROLLED-TEMPERATURE PLASMA SPRAY METHOD AND APPARATUS" which in turn is a continuation-in-part application of application Ser. No. 024,485, filed Mar. 11, 1987, now U.S. Pat. No. 4,788,402 to the applicant and entitled "HIGH POWER EXTENDED ARC PLASMA SPRAY METHOD AND APPARATUS".
US Referenced Citations (5)
Continuations (1)
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193702 |
May 1988 |
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Continuation in Parts (1)
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24485 |
Mar 1987 |
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