METHOD OF MANUFACTURE

Abstract

A method of manufacture of an article or component comprising: providing an intermediate article or component comprising, or consisting essentially of, a precipitation strengthened alloy; and treating the intermediate article or component in accordance with a predetermined heat treatment schedule comprising: a solution treatment step (2), wherein the intermediate article is held at a solution temperature for a first predetermined period of time, the solution temperature being above a solvus temperature (7) and below a solidus temperature (6) for the precipitation strengthened alloy; and a first cooling step (3), wherein the intermediate article is cooled at a first cooling rate of up to 20 C. per minute from the solution temperature to an aging temperature, the aging temperature being below the solvus temperature (7) for the precipitation strengthened alloy.

Claims

1. A method of manufacture of an article or component comprising: providing an intermediate article or component comprising, or consisting essentially of, a precipitation strengthened alloy; and treating the intermediate article or component in accordance with a predetermined heat treatment schedule comprising: a solution treatment step (2), wherein the intermediate article is held at a solution temperature for a first predetermined period of time, the solution temperature being above a solvus temperature (7) and below a solidus temperature (6) for the precipitation strengthened alloy; and a first cooling step (3), wherein the intermediate article is cooled at a first cooling rate of up to 20 C. per minute from the solution temperature to an aging temperature, the aging temperature being below the solvus temperature (7) for the precipitation strengthened alloy.

2. A method of manufacture according to claim 1, wherein the solution temperature is less than 150 C., no more than 125 C., no more than 100 C. or no more than 80 C. below the solidus temperature (6).

3. A method of manufacture according to claim 1, wherein the first predetermined period of time is up to or at least 15 minutes, up to or at least 30 minutes, up to or at least one hour, up to or at least two hours, or up to or at least four hours.

4. A method of manufacture according to claim 1, wherein the predetermined heat treatment schedule further comprises an aging step (4), wherein the intermediate article is held at the aging temperature for a second predetermined period of time.

5. A method of manufacture according to claim 4, wherein the second predetermined period of time is shorter than, longer than or the same as the first predetermined period of time.

6. A method of manufacture according to claim 4, wherein the second predetermined period of time is at least an hour, up to or at least two hours, up to or at least 6 hours, up to or at least 12 hours or up to or at least 24 hours.

7. A method of manufacture according to claim 1, wherein the aging temperature is at least 50 C. or at least 100 C. below the solvus temperature (7) for the precipitation strengthened alloy.

8. A method of manufacture according to claim 1, wherein the predetermined heat treatment schedule further comprises a second cooling step, wherein the intermediate article is cooled from the aging temperature to ambient temperature at a relatively fast rate, e.g. at least 50 C. per minute.

9. A method of manufacture according to claim 8, wherein subsequent to the second cooling step one or more further aging heat treatments are carried out on the intermediate article.

10. A method of manufacture according to claim 1, wherein the predetermined heat treatment schedule is carried out at least in part at an elevated pressure.

11. A method of manufacture according to claim 1, wherein the solution treatment step (2) comprises a hot isostatic pressing (HIP) process.

12. A method of manufacture according to claim 1 further comprising a preliminary step of manufacturing the intermediate article.

13. A method of manufacture according to claim 12, wherein the intermediate article is manufactured using an additive manufacturing process such as additive layer manufacturing.

14. A method of manufacture according to claim 1 wherein the precipitation strengthened alloy is a precipitation strengthened nickel alloy.

15. A method of manufacture according to claim 14, wherein the precipitation strengthened nickel alloy further comprises one or more of: chromium; cobalt; molybdenum; titanium; aluminium; iron; manganese; silicon; and carbon.

16. A method of manufacture of an article or component comprising: providing an intermediate article or component comprising, or consisting essentially of, a precipitation strengthened alloy; and treating the intermediate article or component in accordance with a predetermined heat treatment schedule comprising: a solution treatment step (2), wherein the intermediate article is held at a solution temperature for a first predetermined period of time, the solution temperature being above a solvus temperature (7) and below a solidus temperature (6) for the precipitation strengthened alloy, wherein the solution temperature is less than 150 C. below the solidus temperature (6).

17. A method of manufacture of an article or component comprising: providing an intermediate article or component comprising, or consisting essentially of, a precipitation strengthened alloy; and treating the intermediate article or component in accordance with a predetermined heat treatment schedule comprising: a solution treatment step (2), wherein the intermediate article is held at a solution temperature for a first predetermined period of time, the solution temperature being above a solvus temperature (7) and below a solidus temperature (6) for the precipitation strengthened alloy; and a first cooling step (3), wherein the intermediate article is cooled at a first cooling rate from the solution temperature to an aging temperature, the aging temperature being below the solvus temperature (7) for the precipitation strengthened alloy; wherein the solution treatment step (2) and/or the first cooling step (3) is carried out at elevated pressure.

18. A method of manufacture of an article or component comprising: providing an intermediate article or component comprising, or consisting essentially of, a precipitation strengthened alloy; and treating the intermediate article or component in accordance with a predetermined heat treatment schedule comprising: a solution treatment step (2), wherein the intermediate article is held at a solution temperature for a first period of time, the solution temperature being above a solvus temperature (7) and below a solidus temperature (6) for the precipitation strengthened alloy; wherein the solution treatment step (2) is carried out at elevated pressure.

19. A method of manufacture of an article or component comprising: providing an intermediate article or component comprising, or consisting essentially of, a precipitation strengthened alloy; and treating the intermediate article or component in accordance with a predetermined heat treatment schedule comprising: a solution treatment step (2), wherein the intermediate article is held at a solution temperature for a first predetermined period of time, the solution temperature being above a solvus temperature (7) and below a solidus temperature (6) for the precipitation strengthened alloy; and a first cooling step (3), wherein the intermediate article is cooled at a first cooling rate of up to 20 C. per minute from the solution temperature to ambient temperature.

20. An article or component manufactured according to a method of claim 1.

21. A gas turbine engine (10) comprising an article or component according to claim 20.

Description

[0082] FIG. 1 illustrates an example of a heat treatment;

[0083] FIG. 2 shows a microstructure of an additively manufactured article consisting essentially of a precipitation strengthened nickel alloy following a standard wrought heat treatment;

[0084] FIG. 3 shows a microstructure of an additively manufactured article consisting essentially of a precipitation strengthened nickel alloy following a heat treatment as exemplified by FIG. 1;

[0085] FIG. 4 shows another microstructure of an additively manufactured article consisting essentially of a precipitation strengthened nickel alloy following a heat treatment as exemplified by FIG. 1; and

[0086] FIG. 5 is a sectional side view of a gas turbine engine.

[0087] FIG. 1 illustrates an example of a heat treatment that may be applied to an intermediate article consisting essentially of a precipitation strengthened nickel alloy. Temperature is on the y-axis and time is on the x-axis. A first dashed line 7 indicates the solvus temperature for the precipitation strengthened nickel alloy. A second dashed line 6 indicates the solidus temperature for the precipitation strengthened nickel alloy.

[0088] Generally, the heat treatment comprises a heating step 1, a solution treatment step 2, a first cooling step 3, an aging step 4 and a second cooling step 5.

[0089] The intermediate article is placed in a furnace in an inert atmosphere. In the first heating step 1, the temperature of the furnace is ramped up to a solution treatment temperature. The solution temperature is selected such that it is above the solvus temperature and below the solidus temperature for the precipitation strengthened nickel alloy. The solution temperature may be less than 150 C., no more than 125 C., no more than 100 C. or no more than 80 C. below the solidus temperature. The solution temperature may vary depending upon, among other things, the composition of the precipitation strengthened nickel alloy. For example, the solution temperature may be at least 1200 C. and/or up to 1300 C. The solution temperature may be approximately 1250 C.

[0090] In the solution treatment step 2, the intermediate article is held at the solution temperature for a first predetermined period of time. The first predetermined period of time may vary depending upon, among other things, the composition of the precipitation strengthened nickel alloy. For example, the first predetermined period of time may be up to or at least 15 minutes, up to or at least 30 minutes, up to or at least one hour, up to or at least two hours, or up to or at least four hours. The first predetermined period of time may be approximately one hour.

[0091] In the first cooling step 3, the intermediate article is cooled in the furnace at a relatively slow rate to an aging temperature. The aging temperature is below the solvus temperature of the precipitation strengthened nickel alloy. The cooling rate and/or aging temperature may vary depending upon, among other things, the composition of the precipitation strengthened nickel alloy. In the first cooling step 3, the intermediate article may be cooled at a rate of up to or at least 5 C. per minute and/or up to 20 C. per minute. For example, the intermediate article may be cooled at a rate of approximately 10 C. per minute. The cooling rate may be constant or may vary during the first cooling step 3. The aging temperature may be at least 50 C. or at least 100 C. below the solvus temperature for the precipitation strengthened nickel alloy. The aging temperature may be approximately 790 C. The aging temperature may be approximately 700 C. The aging temperature may be up to or at least 500 C., up to or at least 600 C., up to or at least 700 C., up to or at least 800 C. or up to or at least 900 C.

[0092] In the aging step 4, the intermediate article is held at the aging temperature for a second predetermined period of time. The aging step 4 may be of a longer duration or a shorter duration than the solution treatment step 2, i.e. the second predetermined period of time may be longer or shorter than the first predetermined period of time. The aging step 4 may be of the same duration as the solution treatment step 2, i.e. the second predetermined period of time may be the same as the first predetermined period of time. The second predetermined period of time may be at least an hour, up to or at least two hours, up to or at least 6 hours, up to or at least 12 hours or up to or at least 24 hours. For example, the second predetermined period of time may be approximately eight hours. The second predetermined period of time may vary depending upon, among other things, the composition of the precipitation strengthened nickel alloy.

[0093] In the second cooling step 5, the intermediate article is cooled from the aging temperature to ambient temperature (e.g. room temperature) at a relatively fast rate, e.g. at least 50 C. per minute. Gas fan quenching or air cooling may be utilised to cool the intermediate article at such a fast rate. The cooling rate may be constant or may vary during the second cooling step 5.

[0094] The intermediate article may have been manufactured using an additive manufacturing process such as additive layer manufacturing. After the heat treatment, and one or more optional machining and/or finishing steps, a finished article may be provided. The finished article may form a component or a part thereof for use in a gas turbine engine, e.g. of an aircraft.

[0095] As a result of the first cooling step 3 being carried out at a relatively slow rate, the heat treatment may not require a stabilisation or primary aging step to be carried out at a temperature between the solution temperature and the aging temperature.

[0096] The solution temperature may be relatively high compared with known heat treatments for precipitation strengthened nickel alloys, in which the solution temperature is typically 150 C. or more below the solidus temperature.

[0097] In an embodiment, the intermediate article may be cooled at a relatively slow rate from the solution temperature to ambient temperature (e.g. room temperature) without being held for a period of time at an aging temperature between the solution temperature and ambient temperature. Thus, in an embodiment, the heat treatment may not include the aging step 4 and the second cooling step 5.

[0098] In an embodiment, the heat treatment may be carried out at least in part at an elevated pressure. For instance, the solution treatment step 2 may be carried out at an elevated pressure.

[0099] The solution treatment step 2 may comprise a hot isostatic pressing (HIP) process. Thus, a HIP step may be combined with the solution treatment step 2. Conventionally, the HIP step would be carried out prior to solution heat treatment.

[0100] The aging step 4 may be carried out at atmospheric pressure.

[0101] FIG. 2 shows a microstructure of an additively manufactured article consisting essentially of a precipitation strengthened nickel alloy following a standard wrought heat treatment.

[0102] FIG. 3 shows a microstructure of an additively manufactured article consisting essentially of a precipitation strengthened nickel alloy following a heat treatment as exemplified by FIG. 1 and described above.

[0103] FIG. 4 shows another microstructure of an additively manufactured article consisting essentially of a precipitation strengthened nickel alloy following a heat treatment as exemplified by FIG. 1 and described above.

[0104] The articles shown in FIGS. 2, 3 and 4 consist essentially of the same precipitation strengthened nickel alloy. The alloy has the nominal composition set out in Table 1.

TABLE-US-00003 TABLE 1 Element Weight % Nickel Balance (approximately 57) Chromium 20 Cobalt 10 Molybdenum 8.5 Titanium 2.1 Aluminium 1.5 Iron No more than 1.5 Manganese No more than 0.3 Silicon No more than 0.15 Carbon 0.06 Boron 0.005

[0105] The microstructures shown in FIG. 3 and FIG. 4 exhibit desired grain growth for high temperature capability.

[0106] The microstructures shown in FIG. 3 and FIG. 4 have a multimodal distribution.

[0107] The microstructures shown in FIG. 3 and FIG. 4 have coarser secondary , whereas the microstructure shown in FIG. 2 has very fine tertiary . The tertiary of FIG. 2 may coarsen during service, e.g. in a hot section of a gas turbine engine, which may result in loss of performance. The microstructures shown in FIG. 3 and FIG. 4 have coarsened during heat treatment. Consequently, a material of known properties can be put into service, which won't lose performance further.

[0108] The microstructures shown in FIG. 3 and FIG. 4 have serrated grain boundaries. Serrated grain boundaries may improve resistance to crack growth.

[0109] The microstructures shown in FIG. 3 and FIG. 4 comprise discrete carbides. In contract, the microstructure of FIG. 2 comprises continuous carbides or chains of carbides.

[0110] With reference to FIG. 5, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, an intermediate pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, an intermediate pressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20. A nacelle 21 generally surrounds the engine 10 and defines both the intake 12 and the exhaust nozzle 20.

[0111] The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the air flow directed into it before delivering that air to the high pressure compressor 15 where further compression takes place.

[0112] The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.

[0113] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

[0114] Articles manufactured in accordance with this disclosure may be suitable for use as components in a wide variety of applications within a gas turbine engine, e.g. an aircraft gas turbine engine. More particularly, such articles may be suitable for use as components in the hot section of an aircraft gas turbine engine. Such articles may be suitable for use as components in compressor, combustor and/or turbine sections of a gas turbine engine. Such articles may be suitable for use as exhaust and nozzle components.

[0115] Examples of components comprising, or consisting essentially of, articles manufactured in accordance with this disclosure may include rings, casings and liners for use in compressor, combustor and/or turbine sections of a gas turbine engine.

[0116] Articles manufactured in accordance with this disclosure may be suitable for use as components in land-based turbine applications.

[0117] Employing a higher solution temperature (e.g. less than 150 C., no more than 125 C., no more than 100 C. or no more than 80 C. less than the solidus temperature) may help to achieve recovery and recrystallisation of the microstructure. Further, it may help to achieve desired grain growth for high temperature capability.

[0118] Employing a higher solution temperature and/or a slower cooling rate may help to produce a microstructure having a multimodal distribution, which may comprise relatively coarse secondary . Further, the microstructure may comprise serrated grain boundaries, which may provide resistance to crack growth. The microstructure may comprise discrete carbides.

[0119] The heat treatment of the present disclosure typically may not include a stabilisation step or primary aging step.

[0120] It will be understood that the invention is not limited to the embodiments described above and various modifications and improvements can be made without departing from the concepts herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.