Method and apparatus for effecting high-energy dynamic coating of substrates

Claim 2

Apparatus for effecting spray-coating of a substrate, which comprises: a. means to define an environmental chamber, b. means to reduce the pressure in said chamber to a value below atmospheric pressure, c. an electrical plasma-jet torch positioned to direct a jet of plasma into said chamber, against a substrate disposed in said chamber, d. means to supply spray powder to said plasma jet for heating therein and subsequent impingment against said substrate, and e. means to effect preheating of said spray powder to an elevated temperature prior to the time said spray powder reaches said plasma, said preheating means cooperating with said plasma-jet torch to effect a high degree of heating of said powder prior to the time that said powder impinges upon said substrate.

Claim 3

The invention as claimed in claim 1, in which said torch supplies said plasma to said chamber at a velocity in excess of Mach 1.

Claim 4

The invention as claimed in claim 1, in which a source of electrical power is connected between said torch and said substrate, to supply additional electrical energy to said plasma while it travels toward said substrate.

Claim 5

The invention as claimed in claim 1, in which said powder-supply means recited in clause (d) comprises at least one tube supplied by a source of spray powder and carrier gas, said tube being adapted to conduct said spray powder and carrier gas to plasma generated by said torch, and in which said preheating means recited in clause (e) comprises means to effect heating of said spray powder while in said tube.

Claim 6

The invention as claimed in claim 4, in which said means to heat said spray powder while in said tube comprises means to effect heating of said tube.

Claim 7

The invention as claimed in claim 5, in which said tube is electrically conductive, and in which said means to effect heating of said tube comprises means to effect flow of heating current through said tube.

Claim 8

The invention as claimed in claim 6, in which said tube is formed of metal having a relatively high electrical resistance.

Claim 9

The invention as claimed in claim 1, in which said powder supply means recited in clause (d) comprises a plurality of sources of spray powder and carrier gas, and means to effect simultaneous flow of powder and gas from said sources to the plasma generated by said torch.

Claim 10

The invention as claimed in claim 1, in which said plasma-jet torch comprises a back electrode and a nozzle electrode, means to maintain a high-current electric arc between said back and nozzle electrodes, and means to supply arc gas to the space between said electrodes for heating by said arc and passing through said nozzle electrode into said chamber in the form of high-temperature plasma.

Claim 11

The invention as claimed in claim 9, in which said means to effect preheating of said spray powder effects supplying of said spray powder to the interior of said torch.

Claim 12

The invention as claimed in claim 10, in which said means to effect preheating of said spray powder effects supplying of said spray powder to the nozzle passage through said nozzle electrode, and comprises at least one powder-introduction passage communicating transversely with said nozzle passage.

Claim 13

The invention as claimed in claim 11, in which said powder-introduction passage delivers powder to said nozzle passage in a generally upstream direction relative to the direction of plasma flow throUgh said nozzle passage.

Claim 14

The invention as claimed in claim 12, in which said nozzle passage includes a throat and an end portion diverging from said throat to an exit, said powder introduction passage including a section extending along said diverging end portion and communicating with said throat.

Claim 15

Apparatus for effecting spray-coating of a powder onto a substrate, which comprises: a. an electrical plasma torch comprising a back electrode and a nozzle electrode having a nozzle passage, b. means to maintain a high-current electric arc between said electrodes, c. means to introduce arc gas into the space between said electrodes, whereby said gas is heated by said arc and then passes outwardly through the nozzle passage of said nozzle electrode, d. means to introduce spray powder into said nozzle passage, said spray powder means comprising at least one powder-introduction passage extending through the side wall of said nozzle pasage, and e. means to effect a substantial amount of preheating of said spray powder prior to the time it passes through said nozzle passage wall and into the hot gas in said nozzle passage, said hot gas combining with said preheating means to achieve a highly effective heating of said spray powder.

Claim 16

Apparatus for effecting spray-coating of a powder onto a substrate, which comprises: a. an electrical plasma torch comprising a back electrode and a nozzle electrode having a nozzle passage, b. means to maintain a high-current electric arc between said electrodes, c. means to introduce arc gas into the space between said electrodes, whereby said gas is heated by said arc and then passes outwardly through the nozzle passage of said nozzle electrode, d. means to introduce spray powder into said nozzle passage, said spray powder means comprising at least one powder-introduction passage extending through the side wall of said nozzle pasage, and e. means to effect a substantial amount of preheating of said spray powder prior to the time it passes through said nozzle passage wall and into the hot gas in said nozzle passage, said hot gas combining with said preheating means to achieve a highly effective heating of said spray powder.

Claim 17

The invention as claimed in claim 14, in which said preheating means comprises a powder tube communicating with said powder-introduction passage, said powder tube being formed of metal having a substantial electrical resistance, and means to pass a high current through said powder tube to heat the same and thus the spray powder flowing therethrough.

Claim 18

The invention as claimed in claim 15, in which said means to introduce spray powder further comprises means to introduce spray powder and carrier gas into said powder tube.

Claim 19

Apparatus for effecting spray-coating of a powder onto a substrate, which comprises: a. an electrical plasma torch comprising a back electrode and a nozzle electrode having a nozzle passage, b. means to maintain a high-current electric arc between said electrodes, c. means to introduce arc gas into the space between said electrodes, whereby said gas is heated by said arc and then passes outwardly through the nozzle passage of said nozzle electrode, d. means to introduce spray powder into said nozzle passage, said spray powder means comprising at least one powder-introduction passage extending through the side wall of said nozzle passage, and e. means to effect a substantial amount of preheating of said spray powder prior to the time it passes through said nozzle passage wall and into the hot gas in said nozzle passage, said hot gas combining with said preheating means to achieve a highly effective heating of said spray powder, said preheating means comprising a powder tube communicating with said powder-introduction passage, said powder tube being formed of metal having a substantial electrical resistance, and means to pass a high current through said powder tube to heat the same and thus the spray powder flowing therethrough, said means to pass current through said powder tube comprising a powder-preheat power source one terminal of which is connected to said tube and the other terminal of which is connected to said nozzle electrode, and means to electrically connect said nozzle electrode to said powder tube.

Claim 20

Apparatus for effecting spray-coating of a powder onto a substrate, which comprises: a. an electrical plasma torch comprising a back electrode and a nozzle electrode having a nozzle passage, b. means to maintain a high-current electric arc between said electrodes, c. means to introduce arc gas into the space between said electrodes, whereby said gas is heated by said arc and then passes outwardly through the nozzle passage of said nozzle electrode, d. means to introduce spray powder into said nozzle passage, said spray powder means comprising at least one powder-introduction passage extending through the side wall of said nozzle passage, and e. means to effect a substantial amount of preheating of said spray powder prior to the time it passes through said nozzle passage wall and into the hot gas in said nozzle passage, said hot gas combining with said preheating means to achieve a highly effective heating of said spray powder, said preheating means comprising a powder tube communicating with said powder-introduction passage, said powder tube being formed of metal having a substantial electrical resistance, and means to pass a high current through said powder tube to heat the same and thus the spray powder flowing therethrough, said means to pass current through said powder tube comprising a powder-preheat power source one terminal of which is connected to said tube and the other terminal of which is connected to said nozzle electrode, and means to electrically connect said nozzle electrode to said powder tube.

Claim 21

The invention as claimed in claim 17 in which said means to maintain a high-current electric arc between said electrodes recited in clause (b) comprises a DC power source the negative terminal of which is connected to said back electrode and the positive terminal of which is connected to said nozzle electrode, and in which said powder preheat power source comprises a second DC power source the negative terminal of which is connected to said tube and the positive terminal of which is connected to said nozzle electrode.

Claim 22

The invention as claimed in claim 17, in which said means to connect sAid nozzle electrode to said powder tube comprises a split electrically conductive clamp ring connected to said powder tube, and means to clamp said ring on said nozzle electrode.

Claim 25

The invention as claimed in claim 20, in which said method further comprises causing the pressure in said chamber to be below one-half atmosphere.

Claim 26

The invention as claimed in claim 21, in which said method further comprises causing the pressure in said chamber to be below 40 mm of mercury.

Claim 27

The invention as claimed in claim 20, in which said method further comprises so adjusting the temperature of said jet and other parameters that said particles are soft, but not molten, at the instant when they impinge against said substrate.

Claim 28

The invention as claimed in claim 20, in which said step of preheating comprises effecting preheating of said particles of spray material prior to said entraining step recited in clause (d).

Claim 29

The invention as claimed in claim 20, in which said method further comprises passing an electrict current through said jet to said substrate prior to commencement of said entraining step recited in clause (d), whereby to preheat said substrate.

Claim 30

The invention as claimed in claim 20, in which said method further comprises directing said jet against said substrate after cessation of said entraining step recited in clause (d), whereby to post-anneal said coated substrate.

Claim 31

The invention as claimed in claim 20, in which said method further comprises generating said gas jet by means of a high-current electrical plasma-jet torch.

Claim 32

The invention as claimed in claim 27, in which said substrate is electrically conductive, and including the step of passing a large electrical transfer current through said jet by means of a circuit which includes said substrate.

Claim 33

The invention as claimed in claim 28, in which said transfer current is caused to be sufficiently large to effect localized fusion of said substrate.

Claim 36

The invention as claimed in claim 30, wherein said step of preheating particles and cuasing them to be entrained includes the step of flowing the particles through a heating tube and then through the wall of the nozzle electrode in a direction that extends rearwardly at an acute angle relative to the inner surface of said nozzle passage.

Claim 37

The invention as claimed in claim 30, in which said method further comprises so regulating the amount of said preheating effected by step (d), and so regulating the temperature of said jet, that said particles are soft but not liquid at the instant of impingement against said substrate.

Claim 38

The invention as claimed in claim 30, in which said method further comprises causing the Velocity of the gas in said jet to have a velocity in the range of Mach 1 to Mach 5.

Claim 39

The invention as claimed in claim 33, in which said method further comprises causing said substrate to be disposed, during performance of said spray-coating method, in an environmental chamber the pressure in which is only a small fraction of atmospheric pressure.

Claim 40

The invention as claimed in claim 30, in which said method further comprises introducing said spray material into said gas through the wall of said nozzle passage, and effecting said preheating by passing said spray material through a hot conduit which communicates with said nozzle passage.

Claim 43

The invention as claimed in claim 36, in which said method further comprises causing the pressure in said chamber to be below one half atmosphere, introducing said spray powder into said jet by passing said powder and a carrier gas through the wall of the nozzle passage in said spray torch, and preheating said spray powder by passing the same through a hot elongated tube prior to said passing of said powder through the wall of said nozzle passage.

Claim 44

The invention as claimed in claim 37, in which said method further comprises passing a large electric current through said jet between said torch and said substrate.

Claim 45

The invention as claimed in claim 38, in which said method further comprises employing said large electric current to preheat said substrate prior to said introduction of spray powder, and employing said jet to post-anneal said substrate subsequent to cessation of said introduction of spray powder.

Claim 48

The method of claim 40 including the step of heating said spray material before it is injected into said plasma stream.

Claim 49

The method of claim 41 including the steps of providing an environmental chamber, reducing and maintaining the pressure in said chamber to a value far below atmospheric pressure, mounting the substrate to be coated within said chamber, and projecting said super-sonic plasma stream with the particles of spray material entrained therein into said chamber to impinge upon said substrate.

Claim 52

The method of claim 43 including the step of heating said particles in flight by passing an electrical current from said nozzle to a substrate to be coated by said particles, said electrical current passing through said super-sonic plasma stream.

Claim 53

The method of claim 44 wherein said step of passing an electrical current from said nozzle to said substrate is initiated before the step of injecting a stream of particles into the plasma stream so that the substrate is preheated before the particles impinge thereon.