Method for refurbishing a service-degraded component of a gas turbine

• US 20060016527A1
• Filed: 06/10/2005
• Published: 01/26/2006
• Est. Priority Date: 06/11/2004
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Ishii, Junji, Aburatani, Yoshihiro, Yoshioka, Yomei, Saito, Daizo
• Granted Patent: US 7,632,363 B2
• Time in Patent Office: Days
• US Class Current: 148/671
• CPC Class Codes: B23P 6/002 Repairing turbine components, e.g. moving or stationary blades, rotors, B23P6/045 takes precedence
• CPC Class Codes: C21D 9/0068 for particular articles not mentioned below
• CPC Class Codes: C22F 1/02 in inert or controlled atmosphere or vacuum adjusting the composition of the atmosphere C21D1/76
• CPC Class Codes: C22F 1/10 of nickel or cobalt or alloys based thereon
• CPC Class Codes: C23C 4/02 Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• CPC Class Codes: F01D 5/286 Particular treatment of blades, e.g. to increase durability or resistance against corrosion or erosion F01D5/288 takes precedence
• CPC Class Codes: F05D 2230/80 Repairing, retrofitting or upgrading methods
• CPC Class Codes: F05D 2230/90 Coating; Surface treatment
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft
• CPC Class Codes: Y10T 29/49318 Repairing or disassembling

Abstract

A method for refurbishing service-degraded gas turbine component can recover the microstructure of the alloy of the gas turbine component, whose material is deteriorated or damaged after its operation, to the extent that is equivalent or more than the characteristic at the time of its manufacture. The method comprises performing a recovery heat treatment, performing a solution heat treatment, and performing an aging heat treatment. The recovery heat treatment heat-treats the component under a predetermined pressure, which is higher than normal pressure, wherein the temperature of the component is increased to a predetermined temperature under the predetermined pressure. The solution heat treatment is processed under reduced pressure or inert gas atmosphere after the recovery heat treatment. The aging heat treatment is processed under reduced pressure or inert gas atmosphere after the recovery heat treatment.

Claims

1. A method for refurbishing a service-degraded component formed of a precipitation strengthening type of alloy for a gas turbine, comprising:

performing a recovery heat treatment on the component in an environment having a predetermined pressure that is greater than atmospheric pressure,

wherein the temperature of the component is increased to a predetermined temperature in the environment having the predetermined pressure;

performing a solution heat treatment, which is processed under reduced pressure or inert gas atmosphere, the solution heat treatment being performed after performing the recovery heat treatment; and

performing an aging heat treatment, which is processed under reduced pressure or an inert gas atmosphere, the aging heat treatment being performed after performing the recovery heat treatment.

2. The method for refurbishing a service-degraded component according to claim 1, wherein the step of performing recovery heat treatment further comprises, after starting the recovery heat treatment, decreasing the temperature of the component from the predetermined temperature before starting decreasing the pressure from the predetermined pressure.

3. The method for refurbishing a service-degraded component according to claim 1, wherein the step of performing recovery heat treatment comprises:

increasing pressure of the component to the predetermined pressure, wherein the predetermined pressure can prevent the component from incipient melting;

retaining the pressure at the predetermined pressure; and

increasing the temperature of the component to the predetermined temperature after the pressure has reached the predetermined pressure,

wherein the predetermined temperature is more than at least one of a solvus temperature of γ

′

phases in the alloy or the incipient melting temperature of the component.

4. The method for refurbishing a service-degraded component according to claim 3, wherein the recovery heat treatment further comprises:

decreasing the temperature of the component from the predetermined temperature using a cooling rate, and;

decreasing the pressure of the component from the predetermined pressure after the temperature is decreased to less than at least one of the solvus temperature of γ

′

phases in the alloy or the incipient melting temperature of the component.

5. The method for refurbishing a service-degraded component according to claim 4, wherein the cooling rate is in a range between 10 and 100 degrees centigrade per minute.

6. The method for refurbishing a service-degraded component according to claim 4, wherein the cooling rate is in a range between 20 and 40 degrees centigrade per minute.

7. The method for refurbishing a service-degraded component according to claim 1,

wherein the alloy includes Ni base metal,

wherein a main precipitation strengthening phases are γ

′

phases.

8. The method for refurbishing a service-degraded component according to claim 7,

wherein the alloy has been subjected to a heat treatment at time of manufacture, whose maximum temperature is less than a solvus temperature after the alloy had been cast at time of manufacture, the solvus temperature being a temperature at which the γ

′

phases can be dissolved in γ

phases as its base metal.

9. The method for refurbishing a service-degraded component according to claim 7, wherein the alloy has been subjected to a heat treatment at time of manufacture after the alloy had been cast at time of manufacture,

wherein the heat treatment enables γ

′

phases dissolved partially in γ

phases as its base metal.

10. The method for refurbishing a service-degraded component according to claim 7, further comprising:

inspecting the γ

′

phases in the alloy of the component,

wherein the step of performing the recovery heat treatment is performed to the components having an coarsened γ

′

phases including sizes larger than 0.7 μ

m.

11. The method for refurbishing a service-degraded component according to claim 1, wherein;

the component includes at least one element selected from the group consisting of B, Zr, Hf and C.

12. The method for refurbishing a service-degraded component according to claim 1, wherein;

the recovery heat treatment is performed during an expected life of the component.

13. The method for refurbishing a service-degraded component according to claim 1, wherein the recovery heat treatment is performed when the component reaches its estimated life based on an examination of the component.

14. The method for refurbishing a service-degraded component according to claim 1, wherein the recovery heat treatment is performed before the local creep strain of the component reaches 2%.

15. A gas turbine component refurbished by the method according to claim 1.

16. A gas turbine, comprising the gas turbine component according to claim 15.

17. The method for refurbishing a service-degraded component according to claim 3, wherein the predetermined temperature is greater than both the solvus temperature of γ

′

phases in the alloy and the incipient melting temperature.

18. The method for refurbishing a service-degraded component according to claim 1, wherein the step of performing recovery heat treatment comprises:

increasing pressure of the component in order to prevent the component from incipient melting; and

thereafter increasing the temperature of the component to the predetermined temperature for performing the heat treatment recovery.

19. The method for refurbishing a service-degraded component according to claim 1, wherein the resulting component has γ

′

phases having a size in a range between 0.3 and 0.7 μ

m.

20. A method for refurbishing or strengthening a component formed of a precipitation strengthening type of alloy, comprising:

performing a recovery heat treatment on the component in an environment having a first predetermined pressure greater than atmospheric pressure and a predetermined temperature, wherein the pressure is increased above a second predetermined pressure before the temperature is increased to the predetermined temperature, and

wherein the first predetermined pressure is equal to or greater than the second predetermined pressure.

21. The method of refurbishing or strengthening a component according to claim 20, further comprising:

performing a solution heat treatment, which is performed under reduced pressure or inert gas atmosphere, the solution heat treatment being performed after the recovery heat treatment; and

performing an aging heat treatment, which is performed under reduced pressure or an inert gas atmosphere, the aging heat treatment being performed after the solution heat treatment.

22. The method of refurbishing or strengthening a component according to claim 21, wherein the second predetermined pressure is such that raising the pressure above the second predetermined pressure prevents incipient melting of the alloy of the component.

23. A method for refurbishing or strengthening a component formed of a precipitation strengthening type of alloy, comprising:

performing a recovery heat treatment to the component in an environment having a predetermined pressure greater than atmospheric pressure and a predetermined temperature,

wherein an environmental condition of the environment is adjusted to prevent incipient melting of the alloy of the component before the temperature is increased to the predetermined temperature;

performing a solution heat treatment, which is performed under reduced pressure or inert gas atmosphere, the solution heat treatment being performed after the recovery heat treatment; and

performing an aging heat treatment, which is performed under reduced pressure or an inert gas atmosphere, the aging heat treatment being performed after the recovery heat treatment.

24. The method for refurbishing or strengthening a component of claim 23, wherein the step of adjusting of the environmental condition raises the incipient melting temperature of the component above the predetermined temperature.

25. The method for refurbishing or strengthening a component of claim 24, wherein the environmental condition is pressure.

26. A gas turbine having a component refurbished or strengthened by carrying out a method for refurbishing a gas turbine component comprising the steps of claim 23.