Electrospark deposition system for repair of gas turbine

Abstract

A system and method for repairing a metal substrate includes an electrospark device and an electrode removably supported in the electrode holder. The electrospark device applies a coating of a material when placed into contact with the metal substrate. A cooling device to lowers the temperature of shielding gas flow below an ambient temperature. A conduit is arranged to direct a flow of the shielding gas to the interface of the electrode and the substrate to cool the area of the substrate receiving the coating.

Claims

1. A system for repairing a metal substrate comprising: an electrospark device including an electrode holder and a consumable electrode removably supported in the electrode holder, the electrospark device being arranged and disposed to establish a continuous spark between the consumable electrode and the metal substrate and continuously deposit an alloyed coating until a desired coating thickness is obtained; a cooling device configured to lower the temperature of a shielding gas flow below an ambient temperature; and a conduit isolated from the electrospark device, disposed adjacent to an interface of the consumable electrode and the metal substrate, and oriented toward the interface of the consumable electrode and the metal substrate, wherein the conduit is arranged and disposed to receive the shielding gas flow from the cooling device and direct the shielding gas flow to the interface of the consumable electrode and the metal substrate, the conduit being further arranged and disposed to deliver the shielding gas flow independent of the electrospark device.

2. The system of claim 1, wherein the interface is located at a point of contact of the consumable electrode with the metal substrate where an electrospark is generated.

3. The system of claim 1, wherein the consumable electrode is secured to a nozzle tip under an applied torque to establish the continuous spark between the consumable electrode and the metal substrate to build up a surface of the metal substrate.

4. The system of claim 1, wherein the metal substrate is mounted in a rotatable positioner.

5. The system of claim 4, wherein the rotatable positioner has a rotary speed adjustment.

6. The system of claim 1, wherein the electrode holder is rotatable.

7. The system of claim 6, wherein a rotational speed of the electrode holder is adjustable.

8. The system of claim 1, wherein the metal substrate comprises a fuel nozzle tip.

9. The system of claim 1, wherein the consumable electrode and the metal substrate are cooled by the shielding gas passing through the conduit.

10. The system of claim 1, wherein the temperature of the electrode and an area of the metal substrate surrounding the electrode during electrospark deposition is less than 200 F.

11. The system of claim 1, wherein the alloyed coating ranges in thickness from about 2 mils to about 10 mils.

12. The system of claim 1, wherein the electrospark device is arranged and disposed to form a metallurgical bond between the metal substrate and the alloyed coating.

13. The system of claim 12, wherein the consumable electrode comprises an electrode material suitable for forming a metallurgical bond with the metal substrate.

14. The system of claim 1, wherein the electrospark device is arranged and disposed to establish the continuous spark adjacent to a brazed joint on the metal substrate without thermally damaging the brazed joint.

15. A system for repairing a metal substrate comprising: an electrospark device including a rotatable electrode holder and a consumable electrode removably supported in the rotatable electrode holder, the electrospark device being arranged and disposed to establish a continuous spark between the consumable electrode and the metal substrate and continuously deposit an alloyed coating until a desired coating thickness is obtained; a cooling device configured to lower the temperature of a shielding gas flow below an ambient temperature; and a conduit isolated from the electrospark device, disposed adjacent to an interface of the consumable electrode and the metal substrate, and oriented toward the interface of the consumable electrode and the metal substrate, wherein the conduit is arranged and disposed to receive the shielding gas flow from the cooling device and direct the shielding gas flow to the interface of the consumable electrode and the metal substrate, the conduit being further arranged and disposed to deliver the shielding gas flow independent of the electrospark device, and wherein the interface is located at a point of contact of the consumable electrode with the metal substrate where the continuous spark is established.

16. The system of claim 15, wherein the consumable electrode and the metal substrate are cooled by the shielding gas passing through the conduit.

17. The system of claim 15, wherein the electrospark device is arranged and disposed to form a metallurgical bond between the metal substrate and the alloyed coating.

18. The system of claim 17, wherein the consumable electrode comprises an electrode material suitable for forming a metallurgical bond with the metal substrate.

19. A system for repairing a metal substrate comprising: an electrospark device including a rotatable electrode holder and a consumable electrode removably supported in the rotatable electrode holder, the electrospark device being arranged and disposed to establish a continuous spark between the consumable electrode and the metal substrate and continuously deposit an alloyed coating until a desired coating thickness is obtained; a cooling device configured to lower the temperature of a shielding gas flow below an ambient temperature; and a conduit isolated from the electrospark device, disposed adjacent to an interface of the consumable electrode and the metal substrate, and oriented toward the interface of the consumable electrode and the metal substrate, wherein the conduit is arranged and disposed to receive the shielding gas flow from the cooling device and direct the shielding gas flow to the interface of the consumable electrode and the metal substrate, the conduit being further arranged and disposed to deliver the shielding gas flow independent of the electrospark device, and wherein the consumable electrode and the metal substrate are cooled by the shielding gas passing through the conduit.

20. The system of claim 19, wherein the electrospark device is arranged and disposed to form a metallurgical bond between the metal substrate and the alloyed coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an exemplary fuel nozzle for a gas turbine engine.

(2) FIG. 2 shows a partial cross-sectional view of a brazed joint between a fuel nozzle tip and a body of the fuel nozzle.

(3) FIG. 3 shows an exemplary cooling apparatus for ESD and substrate.

(4) FIG. 4 shows a magnified cross-sectional view of an exemplary repaired nozzle tip.

(5) FIG. 5 shows a process view of an electrospark deposition method, according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF THE INVENTION

(6) Referring to FIGS. 1 and 2, a fuel nozzle 10 includes a nozzle tip 12 in fluid communication with a nozzle body 16 and a fuel gas flow 14 therethrough. Nozzle tip 12 is connected to nozzle body 16 by a brazed joint 18 (FIG. 2).

(7) Referring next to FIG. 3, an electrospark deposition (ESD) process is shown. The ESD provides a suitable thickness of electrode material to repair the substrate, e.g., a fuel nozzle tip 12 (FIG. 1). An electrospark device 21 supports and drives a consumable electrode 20. Electrode 20 is placed into contact with a metal substrate 22, which in this example schematically represents the nozzle tip 12. Electrode 20 is composed of material suitable for forming a metallurgical bond with substrate 22. A shielding gas flow 24 is first introduced to a cooling device 26 to lower the temperature of the shielding gas flow 24 below the ambient temperature. Cooling devices for shielding gases, e.g., argon, nitrogen, or helium, are known to those skilled in the art. Electrode 20 and surrounding substrate 22 of the work piece 12 are cooled by shielding gas 24 passing from cooling device 26 through a supply conduit 28. Supply conduit 28 directs a flow of shielding gas 24 to the interface 30 of electrode 20 and substrate 22.

(8) Gas fuel nozzle tip 12 is mounted in a rotatable positioner having a rotary speed adjustment. The ESD electrode 20 is secured to nozzle tip 12 with an applied torque to establish a continuous spark between electrode 20 and substrate 12, 22 to be repaired. The rotational speed of the ESD electrode may be adjustable as well. Cooled shielding gas 24 is then supplied to the interface 30 of electrode 20 and substrate 12, 22. Shielding gas 24 cools both the substrate 12, 22 surface and the electrode tip in the area of the electrospark. The reduced process temperature allows the coating process to operate continuously until a desired coating thickness is achieved. In one embodiment the temperature of the electrode tip and the area surrounding the electrode tip during the ESD process may be reduced to less than 200 F. In one embodiment a coating thickness ranging between 2 and 10 mils is applied. A thickness of about 2 to 10 mils is sufficient to salvage some worn gas nozzles. In another embodiment a thicker coating of ESD may be deposited if needed.

(9) Referring next to FIG. 4, a magnified cross-section of a repaired nozzle tip 12 shows a fusion bonded interface 36 between the ESD coating 34 and nozzle tip 12. The nozzle tip 12 was repaired using the ESD coating process described above. The brazed joint 18 is undamaged following the ESD coating process.

(10) Referring next to FIG. 5, a flow chart is provided to describe the method of the present disclosure. At step 100, the method begins by placing an ESD electrode into contact with a nozzle tip. At step 102, the method proceeds to cool the shielding gas flow to lower the temperature of the gas. Next, at step 104, the gas fuel nozzle tip is mounted in rotatable positioner having rotary speed adjustment. At step 106, the method proceeds to establish a continuous spark between the ESD electrode and the substrate of the nozzle tip. Next at step 108 the method proceeds by passing cooled shielding gas through a supply conduit to direct flow of shielding gas at the interface of electrode and substrate. Finally, at step 110, the method continues by operating the ESD coating process until a desired coating thickness is applied over the surface of the nozzle tip.

(11) It should be understood that the application is not limited to the details or methodology set forth in the following description or illustrated in the figures. It should also be understood that the phraseology and terminology employed herein is for the purpose of description only and should not be regarded as limiting.

(12) It is important to note that the construction and arrangement of the ESD system as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application.

(13) It should be noted that although the figures herein may show a specific order of method steps, it is understood that the order of these steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. It is understood that all such variations are within the scope of the application. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

(14) While the exemplary embodiments illustrated in the figures and described herein are presently preferred, it should be understood that these embodiments are offered by way of example only. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims. The order or sequence of any processes or method steps may be varied or re-sequenced according to alternative embodiments.