Powder injection for plasma thermal spraying
OwnerGary A. Hislopinventor
Life of this patent
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Abstract
The present invention relates to a plasmatron for a plasma coating apparatus including an anode having an axial bore through which gas is passed around a cathode and an electric arc is established between the anode and cathode. A powder feed line or conduit is connected between the anode and a powder feed source. The feed line has a straight section along a portion of its length terminating at the axial bore of the anode. The straight section of feed line has a ratio of length to internal diameter at least about 4.8, preferably 10 and even more preferably 15.
Claims16
A plasmatron for a plasma coating apparatus, comprising:
- an anode, a cathode, and an axial bore in the anode;
- a powder injection conduit operatively connected to said anode and to a powder feed source, said injection conduit having a relatively straight section along a portion of its length and terminating at said axial bore of said anode;
- and
- said straight section having a length of at least about 4.8 times its internal diameter.
A method of plasma coating objects including:
- evacuating a chamber in a plasmatron to a predetermined vacuum;
- charging the chamber with a non-reactive gas to an operating pressure;
- placing an object in the chamber and in the plasmatron discharge path;
- providing a source of powder to the plasmatron;
- providing a plasma powder injection conduit having a length of at least 4.8 times its diameter;
- creating a plasma stream in the plasmatron;
- and
- feeding powder from the powder source to the plasma stream through the plasma powder injection conduit.
A plasma coating system comprising:
- a plasma spray machine having an internal powder injection conduit, a main chamber, a transfer chamber, at least one gas feed and exhaust conduit, a plasmatron, a DC plasma power supply, an AC plasma power supply, and remotely operable manipulative equipment;
- the internal powder injection conduit having a section of a predetermined length, a predetermined internal diameter, operatively connected to and in communication with an injection powder source and terminating at a bore in the plasmatron anode;
- and
- the internal powder injection conduit has a length of at least about 4.8 times its internal diameter.
Dependencies are inferred from the claim text.