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A plasma arc torch that includes a torch body having a nozzle mounted relative to a composite electrode in the body to define a plasma chamber. The torch body includes a plasma flow path for directing a plasma gas to the plasma chamber in which a plasma arc is formed. The nozzle includes a hollow, b

A plasma arc torch that includes a torch body having a nozzle mounted relative to a composite electrode in the body to define a plasma chamber. The torch body includes a plasma flow path for directing a plasma gas to the plasma chamber in which a plasma arc is formed. The nozzle includes a hollow, body portion and a substantially solid, head portion defining an exit orifice. The composite electrode can be made of a metallic material (e.g., silver) with high thermal conductivity in the forward portion electrode body adjacent the emitting surface, and the aft portion of the electrode body is made of a second low cost, metallic material with good thermal and electrical conductivity. This composite electrode configuration produces an electrode with reduced electrode wear or pitting comparable to a silver electrode, for a price comparable to that of a copper electrode.

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1. A plasma arc torch comprising:a torch body for holding an electrode, the torch body including a plasma flow path for directing a plasma gas to a plasma chamber; a composite electrode; and a nozzle mounted beneath the composite electrode, the nozzle and the composite electrode defining the plasma

1. A plasma arc torch comprising:a torch body for holding an electrode, the torch body including a plasma flow path for directing a plasma gas to a plasma chamber; a composite electrode; and a nozzle mounted beneath the composite electrode, the nozzle and the composite electrode defining the plasma chamber, wherein the composite electrode comprises: an electrode body having a forward portion and an aft portion, the aft portion comprising a first metallic material and having a first mating surface; the forward portion comprising a second metallic material and having a second mating surface configured to join with the first mating surface such that an interior surface of the forward portion is directly cooled by a coolant, the first and second mating surfaces being in direct contact with each other; wherein the first and second metallic materials have a heat transfer property, the value of the heat transfer property for the second material being greater than that of the first metallic material. 2. The plasma arc torch of claim 1, further comprising a bore disposed in a first end of the forward portion of the electrode body, along a central axis passing through the electrode body, and an insert disposed in the bore.3. The plasma arc torch of claim 2, wherein the insert comprises a high thermionic emissivity material comprising hafnium, zirconium, tungsten, thorium, lanthanum, strontium, or alloys thereof.4. The plasma arc torch of claim 1, wherein the first and second mating surfaces are substantially the same size.5. The plasma arc torch of claim 1, wherein the first mating surface and the second mating surfaces have different sizes.6. The plasma arc torch of claim 1, wherein the aft portion of the electrode body comprises a cavity.7. The plasma arc torch of claim 1, wherein the first or second mating surface is planar.8. The plasma arc torch of claim 1, wherein the first or second mating surface is non-planar.9. The plasma arc torch of claim 1, wherein the first and second mating surfaces have different shapes.10. The plasma arc torch of claim 1, wherein the aft portion of the electrode comprises a receiving portion to receive the forward portion of the electrode.11. The plasma arc torch of claim 1, wherein only a single radial interface is provided between an insert and the forward portion of the electrode body.12. The plasma arc torch of claim 1, wherein the second metallic material is selected from the group consisting of silver, brass, silver-copper alloys, platinum, gold, palladium, rhodium, and alloys thereof.13. The plasma arc torch of claim 1, further comprising an internal flow path for allowing a flow of cooling fluid, such that the flowing cooling fluid cools the forward portion of the composite electrode.14. The plasma arc torch of claim 13, wherein the flow of cooling fluid directly cools an insert disposed in a bore at the first end of the forward portion of the electrode body.15. A composite electrode comprising:an electrode body having a forward portion and an aft portion, the aft portion comprising a first metallic material and having a first mating surface; the forward portion comprising a second metallic material and having a second mating surface configured to join with the first mating surface such that an interior surface of the forward portion is directly cooled by a coolant, the first and second mating surfaces being in direct contact with each other; wherein the first and second metallic materials have a heat transfer property, the value of the heat transfer property for the second material being greater than that of the first metallic material. 16. The composite electrode of claim 15, wherein the first mating surface and the second mating surface have different sizes.17. The composite electrode of claim 15, wherein the first or second mating surface is planar.18. The composite electrode of claim 15, wherein the first or second mating surface is non-planar.19. The composite electrode of claim 15, wherein the aft portion of the electrode body comprises a cavity.20. The composite electrode of claim 15, wherein the first mating surface and the second mating surface have different shapes.21. The composite electrode of claim 15, wherein the aft portion of the electrode comprises a receiving portion to receive the forward portion of the electrode.22. The composite electrode of claim 15, wherein the direct contact between the first mating surface and the second mating surface is formed using a direct welding technique such as: friction welding, inertia friction welding, direct drive friction welding, CD percussive welding, percussive welding, ultrasonic welding, or explosion welding.23. The composite electrode of claim 15, wherein the first and second mating surfaces are both circular.24. The composite electrode of claim 15, wherein the first mating surface and the second mating surface are substantially the same size.25. The composite electrode of claim 15, wherein only a single radial interface is provided between an insert and the forward portion of the electrode body.26. The composite electrode of claim 15, wherein the first metallic material is selected from the group consisting of copper, brass, aluminum, and a copper alloy.27. The composite electrode of claim 15, wherein the second metallic material comprises a metal selected from the group consisting of silver, brass, copper-silver alloys, platinum, gold, palladium, rhodium, and alloys thereof.28. The composite electrode of claim 22, wherein the joint forms a hermetic seal.29. The composite electrode of claim 15, further comprising a bore disposed in the first end of the forward portion of the electrode body, along a central axis passing through the forward portion of the electrode body, and an insert disposed in the bore.30. The composite electrode of claim 29, wherein the insert has a substantially cylindrical shape.31. The composite electrode of claim 29, wherein the insert comprises a high thermionic emissivity material comprising hafnium, zirconium, tungsten, thorium, lanthanum, strontium, or alloys thereof.32. The composite electrode of claim 15, further comprising an internal flow path for allowing a flow of cooling fluid, such that the flowing cooling fluid cools the forward portion of the composite electrode.33. The composite electrode of claim 32, wherein the flow of cooling fluid directly cools the forward portion of the electrode body.34. The composite electrode of claim 32, wherein the cooling fluid directly cools an insert.35. A method of manufacturing an electrode, comprising the steps of:providing an aft portion of an electrode body comprising a first metallic material and having a first mating surface; providing a forward portion of the electrode body comprising a second metallic material and having a second mating surface configured to join with the first mating surface, wherein the first and second metallic materials have a heat transfer property, the value of the heat transfer property for the second material being greater than that of the first metallic material; and directly welding the first and second mating surfaces to form a joint. 36. The method of claim 35, wherein the first mating surface and the second mating surface have different sizes.37. The method of claim 35, wherein the aft portion of the electrode body comprises a cavity.38. The method of claim 35, wherein the first mating surface and the second mating surface have different shapes.39. The method of claim 35, wherein the aft portion of the electrode body comprises a receiving portion to receive the forward portion of the electrode.40. The method of claim 35, wherein the direct welding step includes at least one of friction welding, inertia friction welding, direct drive friction welding, CD percussive welding, percussive welding, ultrasonic welding, or explosion welding.41. The method of claim 35, wherein the first or second mating surface is planar.42. The method of claim 35, wherein the first or second mating surface is non-planar.43. The method of claim 35, wherein the second metallic material is selected from the group consisting of silver, brass, silver-copper alloys, platinum, gold, palladium, rhodium, and alloys thereof.44. The method of claim 35, wherein the electrode further comprises an internal flow path for allowing a flow of cooling fluid, such that the flowing cooling fluid cools the forward portion of the electrode.45. The method of claim 44, wherein the flow of cooling fluid directly cools an insert disposed in a bore at a first end of the forward portion of the electrode body.46. The method of claim 40, wherein the joint between the first and second mating surfaces forms a hermetic seal.47. The method of claim 35, wherein the forward portion of the electrode body further comprises a bore disposed in a first end of the forward portion of the electrode body, along a central axis passing through the forward portion of the electrode body, and an insert disposed in the bore.48. The method of claim 47, wherein the insert comprises a high thermionic emissivity material comprising hafnium, zirconium, tungsten, thorium, lanthanum, strontium, or alloys thereof.49. The method of claim 35, wherein the first mating surface and the second mating surface have different shapes.50. The method of claim 47, wherein only a single radial interface is provided between the insert and the forward position of the electrode body.51. A method of cooling a composite electrode comprising:providing an electrode comprising a body having a forward portion and an aft portion, the aft portion comprising a first metallic material and having a first mating surface, the forward portion comprising a second metallic material and having a second mating surface configured to join with the first mating surface; directly contacting the first and second mating surfaces with each other; and circulating coolant across at least one interior surface of the forward portion to cool the electrode.