Method of depositing heat fusible material and apparatus therefor

Claim 1

A plasma spray device comprising an electrode assembly including a conical central electrode and a conical recess electrode in axial alignment, means for forcing an ionizable gas over the surface of the conical electrode and through the conical recess electrode to form a laminar flowing plasma between the two electrodes, a hollow passageway associated with the recess electrode and haVing an open end spaced from the electrodes to form a nozzle for the expulsion of the laminar plasma, said hollow passageway also formed with an annular abrupt step between the electrodes and the outlet nozzle which increases the diameter of the passageway to thereby produce a subregion of turbulence in the laminar flowing plasma adjoining the inside surface of the cylindrical passageway, conduits for carrying fluent particles to the plasma, said conduits having their exit ports in the hollow passageway at its largest diameter adjoining said abrupt step and disposed so as to direct the particles onto the surface of the laminar flowing plasma, gas injection means around the conical central electrode which includes a plurality of conduits spaced around the said conical central electrode and angularly disposed so as to direct the gas to travel through the space between said conical central electrode and said conical recess electrode, the cone angle of the recessed electrode being smaller than the cone angle of the conical central electrode and the difference between the two angles being within the range of 10* to 30*, and electrical means connected to the two electrodes for forming an electrical arc therebetween.

Claim 6

A method of depositing a heat fusible material on a substrate comprising creating a plasma in a laminar flowing gas in a generally cylindrical confined region by an electric discharge between two electrodes, injecting the gas into said region in laminar flow through an annular constriction of gradually changing dimensions adjoining said electrodes, passing the plasma through a constricted conduit while maintaining laminar flow, expanding the plasma at the end of said constricted conduit to produce a subregion of turbulence as a result of the sudden change in diameter of the conduit, said turbulence restricted to the surface of the plasma stream, projecting at least one stream of fluidized heat fusible material into said subregion of turbulence for conveying the material by the plasma stream to a substrate to be coated.

Claim 7

A method of depositing a heat fusible material on a substrate comprising creating a plasma in a laminar flowing gas in a generally cylindrical confined region by an electric discharge between two electrodes, injecting the gas into said region in laminar flow through an annular constriction of gradually changing dimensions adjoining said electrodes, passing the plasma through a constricted conduit while maintaining laminar flow, expanding the plasma at the end of said constricted conduit to produce a subregion of turbulence as a result of the sudden change in diameter of the conduit, said turbulence restricted to the surface of the plasma stream, projecting at least one stream of fluidized heat fusible material into said subregion of turbulence for conveying the material by the plasma stream to a substrate to be coated.