Cobalt-base composition and method for diffusion braze repair of superalloy articles

• US 6,195,864 B1
• Filed: 05/07/1999
• Issued: 03/06/2001
• Est. Priority Date: 04/08/1997
• Status: Expired due to Term

• Current Assignee: Allison Engine Company, Inc. (Rolls-Royce Holdings Plc)
• Original Assignee: Allison Engine Company, Inc. (Rolls-Royce Holdings Plc)
• Inventors: Chesnes, Richard Patrick
• Primary Examiner(s): Echols, P. W.
• Assistant Examiner(s): Omgba, Essama
• Application Number:
  US09/306,968
• Time in Patent Office: 669 Days
• Field of Search: 294/020.1, 294/021.8, 228/262.31, 420/438, 420/437, 420/436, 420/439, 420/435, 148/408, 148/425
• US Class Current: 29/402.01
• CPC Class Codes: B23K 35/0244 Powders, particles or spheres; Preforms made therefrom
• CPC Class Codes: B23K 35/3046 Co as the principal constituent
• CPC Class Codes: Y10T 29/49718 Repairing
• CPC Class Codes: Y10T 29/49746 by applying fluent material, e.g., coating, casting
• CPC Class Codes: Y10T 428/1275 Next to Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/12861 Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/12875 Platinum group metal-base component

Abstract

An improved cobalt-base braze alloy composition and method for diffusion brazing are provided for use in repairing superalloy articles, such as gas turbine engines, power generation turbines, refinery equipment, and heat exchangers. The improved cobalt-base braze alloy composition includes nickel; at least one element selected from the group of rhenium, palladium, platinum, ruthenium, and iridium; at least one element selected from the group of boron and silicon; and the remaining balance consists of cobalt. This composition may also include aluminum and/or one or more rare earth/lanthanide series elements, and the composition may be combined with one or more powdered base metal superalloy compositions to form an improved diffusion braze alloy mixture. In the improved method for repairing superalloy articles, the foregoing mixture is applied to a region of the superalloy article to be repaired. The mixture is then heated to melt the cobalt-base braze alloy, thereby joining the base metal superalloy powder particles together, and joining the entire mixture to the region being repaired. The molten mixture is next subjected to a diffusion braze heat treatment cycle in order to break down undesirable boride and silicide phases and to diffuse the melting point depressants into the mixture. In a preferred embodiment, the long term diffusion heat treatment cycle consists of heating the repaired article to 2000° F., holding that temperature for 2 hours, heating the repaired article to 2100° F., holding that temperature for 22 hours, and cooling the article to 250° F. After cooling, an environmental coating is applied to the final repair composite, and this composite significantly improves the cyclic oxidation resistance of the coating compared to the properties of the superalloy base metal.

Claims

1. A method of repairing a damaged region of a corrosion resistant superalloy substrate comprising:

preparing a repair mixture comprising a cobalt-base braze alloy, a base metal alloy composition and an organic binder, said cobalt-base braze alloy consisting essentially of, in percent by weight;

Nickel from about 0.001% to less than the weight percent of cobalt;

at least one element selected from the group consisting of;

Rhenium from about 0.001% to about 15%,

Palladium from about 0.001% to about 40%,

Platinum from about 0.001% to about 40%,

Iridium from about 0.001% to about 12%, and

Ruthenium from about 0.001% to about 12%;

at least one element selected from the group consisting of;

Boron from about 0.001% to about 6% and

Silicon from about 0.001% to about 10%; and

at least one element from the group consisting of;

Chromium, Aluminum, Titanium, Tungsten, Molybdenium, Niobium, Rhenium, Hafnium, Tantalum, Iron, Manganese, Rare earth/Lanthanide elements, Carbon, and Zirconium; and

the balance Cobalt;

depositing said repair mixture on at least a portion of the damaged region; and

joining the deposited repair mixture to the superalloy substrate.

2. The method of claim 1, wherein said joining includes a long term diffusion heat treatment.

3. The method of claim 2, wherein the long term diffusion heat treatment includes:

heating said depositing repair mixture to a first temperature between about 2000°

F. and about 2100°

F.;

heating the depositing repair mixture to a second temperature greater than or equal to about 2100°

F.;

maintaining the deposited repair mixture at a temperature greater than or equal to about 2100°

F. for between about 20 hours and about 32 hours; and

lowering the temperature of the repair mixture to about 250°

F.

4. The method of claim 3 wherein the deposited repair mixture is maintaining at a temperature between about 2000°

F. and about bout 2100°

F. for about 2 hours.

5. The method of claim 2, wherein the long term diffusion heat treatment includes:

heating said mixture deposited on said damaged region to a temperature of greater than or equal to about 2000°

F.;

decreasing the temperature of the deposited repair mixture from about 2000°

F. to a temperature between about 1999°

F. and about 1600°

F.;

maintaining the deposited repair mixture at a temperature between about 1999°

C. and about 1600°

F. for less than about 20 hours; and

lowering the temperature of the repair mixture to about 250°

F.

6. The method of claim 5 wherein the deposited repair mixture is maintain at a temperature greater than or equal to about 2000°

F. for about 2 hours.

7. The method of claim 1, wherein said joining includes:

heating the deposited repair mixture to a first temperature of between about 800°

F. and about 1800°

F.;

heating the deposited repair mixture to a second temperature greater than or equal to about 1800°

F.;

heating the deposited repair mixture to a third temperature between about 1800°

F. and less than about the incipient melting temperature of the superalloy substrate for between about 15 and about 45 minutes; and

cooling the depositing repair mixture to a temperature of less than or equal to about 1800°

F.

8. The method of claim 7 wherein the deposited repair mixture is maintained at a temperature between about 800°

F. and about 1800°

F. for about 15 minutes.

9. The method of claim 1, wherein the repair mixture comprises at least one additional base metal alloy composition.

10. The method of claim 9, wherein said at least one additional brase alloy composition is not a eutectic alloy.

11. The method of claim 1, and further including:

applying an environmental coating to said to said superalloy.

12. The method of claim 1 wherein said joining includes heating the deposited repair mixture to a temperature of between about 800°

F. and less than the incipient melting temperature of the superalloy.

13. The method of claim 1, wherein said joining includes heating the deposited repair mixture under an inert atmosphere or under subatmospheric conditions.

14. The method of claim 1 wherein said joining includes heating the deposited repair mixture to a temperature sufficient to form a solid solution matrix.

15. The method according to claim 1, wherein the cobalt-base braze alloy composition is prealloyed, and wherein the base metal alloy composition is prealloyed.

16. The method of claim 1, wherein the cobalt-base braze alloy composition of consists essentially of, in percent by weight:

Nickel from about 9.5% to about 11.5%,

Chromium from about 22% to about 24%,

Aluminum from about 0.5% to about 2.5%,

Titanium from about 0.75% to about 2.25%,

Tungsten from about 2% to about 4%,

Platinum up to about 40%,

Palladium up to about 40%,

Rhenium from about 0.001% to about 2%,

Rare earth/Lanthanide series addition up to about 5%,

Tantalum from about 5% to about 7%,

Carbon up to about 1.05%,

Boron from about 0.5% to about 2.5%, and

Silicon from about 4% to about 6; and

the balance cobalt.

17. The method of claim 1, wherein the cobalt base braze composition consists essentially of, in percent by weight:

Nickel from about 9% to about 11%,

Chromium from about 21.5% to about 23.5%,

Titanium from about 0.001% to about 0.25%,

Tungsten from about 6% to about 8%,

Rhenium from about 0.001% to about 15%,

Tantalum from about 2.5% to about 15%,

Platinum up to about 40%,

Palladium up to about 40%,

Rare earth/Lanthanide series addition up to about 5%,

Carbon up to about 1.1%,

Boron from about 0.5% to about 2.5%, and

Silicon from about 4% to about 6,

Zirconium from about 0.01% to about 1.5%; and

the balance cobalt.

18. The method of claim 1, wherein the cobalt base braze composition consists essentially of, in percent by weight:

Nickel from about 29% to about 32%,

Chromium from about 13.75% to about 15.75%,

Aluminum from about 2.3% to about 4.4%,

Tungsten from about 0.3% to about 2.4%,

Rhenium from about 0.001% to about 1.5%,

Tantalum from about 7.8% to about 9.8%,

Hafnium from about 0.001% to about 1.5%,

Rare earth/Lanthanide series addition up to about 5%,

Platinum up to about 40%,

Palladium from about 2% to about 4%,

Carbon up to about 0.8%,

Boron from about 1.3% to about 3.4%, and

Silicon from about 2.3% to about 4.4,

the balance cobalt.

19. The method of claim 1, wherein the repair mixture is provided as a powder metal slurry.

20. The method of claim 1, wherein the repair mixture is provided as a pre-sintered powdered metal alloy tape.

21. The method of claim 1, wherein the repair mixture is provided as a plasticized powdered metal alloy tape.

22. The method of claim 1, wherein the repair mixture is provided as a pre-sintered alloy preform.

23. The method of claim 1, wherein the repair mixture comprises less than or equal to about 50%, by weight based on the total weight of the repair mixture, of the cobalt-base braze alloy composition.

24. The method of claim 1, wherein the repair mixture comprises less than or equal to about 30%, by weight based on the total weight of the repair mixture, of the cobalt base braze alloy composition.

25. A method of repairing a damaged region of a corrosion resistant superalloy substrate comprising:

preparing a repair mixture comprising a cobalt-base braze alloy composition, a base metal alloy composition; and

an organic binder;

wherein the cobalt-base braze alloy composition is a eutectic alloy comprising, in percent by weight;

Nickel from about 0.001% to less than the weight percent of cobalt;

at least one element selected from the group consisting of;

Rhenium from about 0.001% to about 15%,

Palladium from about 0.001% to about 40%,

Platinum from about 0.001% to about 40%,

Iridium from about 0.002% to about 12%, and

Ruthenium from about 0.001% to about 12%; and

the balance Cobalt;

depositing said mixture on said damaged region of said corrosion resistant superalloy substrate; and

joining the repair mixture to the superalloy substrate.

26. A method of repairing a superalloy article, said method comprising a long term diffusion heat treatment of a superalloy mixture of at least one braze alloy and at least one base metal alloy comprising:

providing a solid superalloy mixture of at least one braze alloy and at least one base metal alloy, said solid superalloy mixture including an amount of brittle phases;

heating said solid superalloy mixture to a temperature of at least about 2000°

F.;

increasing the temperature of the solid superalloy mixture to a temperature between about 2100°

F. and a temperature less than the incipient melting temperature of solid superalloy;

maintaining the temperature of the solid superalloy mixture at a temperature between about 2100°

F. and a temperature less than the incipient melting temperature of the solid superalloy for between about 20 and about 32 hours; and

decreasing the temperature of the solid superalloy mixture to a temperature less than or equal to about 250°

F.;

wherein said method homogenizes the solid superalloy mixture and reduces the amount of brittle phases.

27. The method of claim 26 wherein the superalloy mixture is maintained at a temperature of at least about 2000°

F. for about 2 hours.

28. The method of claim 26 wherein said providing comprises a high temperature brazing cycle prior to long term diffusion treatment, said high temperature brazing cycle comprising:

heating a superalloy mixture to a temperature between about 1800°

F. and less than the incipient melting temperature of the superalloy article to be repaired and thereafter decreasing the temperature of the superalloy mixture to a temperature less than the incipient temperature of the article being repaired to about 1800°

F. to provide the solid superalloy mixture.

29. The method of claim 28 wherein the superalloy mixture is heated in the high temperature brazing cycle to a temperature of between about 1°

F. and about 400°

F. higher than in the long term diffusion treatment.