TORCH BRAZING PROCESS AND APPARATUS THEREFOR

• US 20090039062A1
• Filed: 08/06/2007
• Published: 02/12/2009
• Est. Priority Date: 08/06/2007
• Status: Abandoned Application

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Thyssen, Jeffrey Reid, Campbell, John Ralph, Cretegny, Laurent
• Application Number:
  US11/834,528
• Publication Number:
  US 20090039062A1
• Time in Patent Office: Days
• US Class Current: 219/129
• CPC Class Codes: B23K 1/00 Soldering, e.g. brazing, or unsoldering B23K3/00 takes precedence; characterised only by the use of special materials or media B23K35/00; dip or wave soldering in the manufacture of printed circuits H05K3/34
• CPC Class Codes: B23K 1/0018 Brazing of turbine parts
• CPC Class Codes: B23K 10/02 Plasma welding
• CPC Class Codes: B23K 10/027 Welding for purposes other than joining, e.g. build-up welding
• CPC Class Codes: H05H 1/341 Arrangements for providing coaxial protecting fluids

Abstract

A process and apparatus for brazing a metal alloy component, such as a superalloy component of a gas turbine engine. The process employs a plasma torch in a non-transferred arc mode to generate an electric arc between an electrode and a housing in which an orifice is defined. A plasma gas is flowed through the arc so as to ionize the plasma gas, and the resulting ionized plasma gas is discharged through the orifice to form a plasma jet. The plasma torch is configured so that the plasma jet is shrouded from a surrounding oxidizing atmosphere by a shielding gas flowing cocurrently with the plasma jet. A braze alloy material is introduced into the plasma jet, which is directed at a surface of the component to form a brazement that is metallurgically bonded to the component without melting the component.

Claims

1. A torch brazing process comprising:

operating a plasma torch in a non-transferred arc mode to generate an electric arc within the plasma torch between an electrode and a housing in which an orifice is defined, flowing a plasma gas though the electric arc so as to ionize the plasma gas, and discharging the ionized plasma gas though the orifice to form a plasma jet shrouded from a surrounding oxidizing atmosphere by a shielding gas flowing cocurrently with the plasma jet;

while the electric arc continues to be generated between the electrode and the housing, introducing a braze alloy material into the plasma jet; and

while the electric arc continues to be generated between the electrode and the housing, directing the plasma jet at a surface of a substrate formed of a metal alloy to form a brazement metallurgically bonded to the substrate without melting the substrate and without generating an electric arc between the electrode and the substrate.

2. A torch brazing process according to claim 1, wherein the electric arc is generated by a direct current of at least 50 to about 120 amperes.

3. A torch brazing process according to claim 1, wherein the orifice is defined by a portion of the housing formed of tungsten or an alloy thereof, and the electric arc is generated by and between the electrode and the portion of the housing.

4. A torch brazing process according to claim 1, wherein the plasma gas is a mixture of helium and hydrogen, and wherein the plasma gas flows at a rate of about 3 to about 30 liters per minute though the electric arc.

6. A torch brazing process according to claim 1, wherein the plasma gas is a mixture of helium and hydrogen, and wherein the plasma gas contains helium and hydrogen at a volumetric ratio of about 99:

1 to about 95;

5.

7. A torch brazing process according to claim 1, wherein the shielding gas is argon or a mixture of argon and hydrogen, and wherein the shielding gas flows at a rate of about 10 to about 55 liters per minute.

9. A torch brazing process according to claim 1, wherein the shielding gas is argon or a mixture of argon and hydrogen, and wherein the shielding gas exhibits laminar flow around the plasma jet.

10. A torch brazing process according to claim 1, wherein the process is performed without a flux compound.

11. A torch brazing process according to claim 1, wherein the braze alloy material is a rod, and wherein the process is performed without a flux compound.

13. A torch brazing process according to claim 1, wherein the braze alloy material is a rod, and wherein the rod has a coating containing a solid flux compound.

14. A torch brazing process according to claim 13, wherein the solid flux is selected from the group consisting of potassium tetrafluoroaluminate, potassium tetrafluoroborate, and mixtures thereof.

15. A torch brazing process according to claim 1, wherein the surrounding oxidizing atmosphere is atmospheric air.

16. A torch brazing process according to claim 1, wherein the metal alloy of the substrate is a superalloy.

17. A torch brazing process according to claim 16, wherein the superalloy is a gamma-prime strengthened single-crystal nickel-base superalloy.

18. A torch brazing process according to claim 17, wherein the substrate is a portion of a gas turbine engine component.

19. A torch brazing process according to claim 1, wherein the process is a repair process in which a defect in the surface of the substrate is filled by the brazement.

20. A torch brazing process according to claim 1, wherein the process is a joining process in which the brazement joins the surface of the substrate to a second surface.

5. (canceled)

8. (canceled)

12. (canceled)

21. A torch brazing apparatus comprising:

a plasma torch having a housing, an insert within the housing and in which a passage terminating at an orifice is defined, an electrode having an end thereof projecting into but not though the passage so as to define an annular gap with the insert;

means for generating an electric arc within the annular gap between the electrode and the insert;

means for flowing a plasma gas though the annular gap and through the electric arc so as to ionize the plasma gas and discharge the ionized plasma gas through the orifice to form a plasma jet; and

means for flowing a shielding gas cocurrently with the plasma jet so that the flow of the shielding gas is laminar and shrouds the plasma jet from a surrounding oxidizing atmosphere.

22. A torch brazing apparatus according to claim 21, wherein the electric arc generating means comprises a direct current of at least 50 to about 120 amperes.

23. A torch brazing apparatus according to claim 21, wherein the insert is formed of tungsten or an alloy thereof.

24. A torch brazing apparatus according to claim 21, wherein the plasma gas is a mixture of helium and hydrogen, and wherein the plasma gas flowing means is adapted to produce a plasma gas flow rate of about 3 to about 30 liters per minute though the electric arc.

26. A torch brazing apparatus according to claim 21, wherein the plasma gas is a mixture of helium and hydrogen, and wherein the plasma gas contains helium and hydrogen at a volumetric ratio of about 99:

1 to about 95;

5.

27. A torch brazing apparatus according to claim 21, wherein the plasma gas is a mixture of helium and hydrogen, and wherein the plasma gas contains helium and hydrogen at a volumetric ratio of at least 95:

5.

28. A torch brazing apparatus according to claim 21, wherein the shielding gas is argon or a mixture of argon and hydrogen, and wherein the shielding gas flowing means is adapted to produce a shielding gas flow rate of about 10 to about 55 liters per minute.

30. A torch brazing apparatus according to claim 21, wherein the shielding gas is argon or a mixture of argon and hydrogen, and wherein the shielding gas flowing means is configured to induce laminar flow of the shielding gas around the plasma jet.

25. (canceled)

29. (canceled)