Hot working method and product of nickel-based superalloy workpiece

Abstract

The present invention provides a method for hot working a nickel-based high-temperature alloy workpiece and a product thereof. The hot working method comprises: performing stress relief heat treatment on the nickel-based high-temperature alloy workpiece; performing vacuum brazing on the product of the previous step; performing segmented cooling on the product of the previous step, wherein the segmented cooling comprises: a first stage cooling, with a temperature range of T1 to T2 and a cooling rate of 16-20°C / min; a second stage cooling, with a temperature range of T2 to T3 and a cooling rate of 30-35°C / min; a third stage cooling, with a temperature range of T3 to T4 and a cooling rate of 25-30°C / min; T1 = 1035±50°C; T2 = 968±50°C; T3 = 593±50°C; and T4 = 60±30°C; and performing aging heat treatment on the product of the previous step.

Description

Technical Field

[0001] The present invention relates to the field of material processing, and in particular to a thermal processing method and product of a nickel-based high-temperature alloy workpiece. Background Art

[0002] GH4738 precipitation-hardening superalloy has excellent overall properties, particularly high-temperature tensile strength, creep resistance, and oxidation resistance, and has been widely used in aircraft engines. To achieve a tight seal, vacuum brazing is used to join GH4738 superalloy to honeycomb components, such as the high-pressure turbine inner support casing assembly.

[0003] The hot working of GH4738 precipitation-hardening alloy involves a series of thermal cycles, including stress relief before brazing, brazing, and post-braze aging. Improper handling of this process can damage the material's structure, leading to problems such as coarse grains, precipitation of harmful phases, and mismatched size and distribution of strengthening phases. Conventional post-weld aging heat treatment cannot eliminate these negative effects of the thermal cycle during machining, further compromising the forging's performance, resulting in substandard high-temperature durability, notch sensitivity, and difficulty meeting material acceptance standards. Summary of the Invention

[0004] The present application provides an innovative method for thermal processing of nickel-based high-temperature alloy workpieces, which effectively eliminates the adverse effects of processing thermal cycles on the structure and properties of the material.

[0005] In some aspects, the present application provides a method for hot working a nickel-based high-temperature alloy workpiece, comprising:

[0006] Perform stress relief heat treatment on nickel-based high-temperature alloy workpieces;

[0007] Perform vacuum brazing on the product from the previous step;

[0008] The product of the previous step is subjected to stage-by-stage cooling, which includes

[0009] In the first stage, the temperature range is from T1 to T2, and the cooling rate is 16-20℃ / min;

[0010] The second stage is cooling, the temperature range is from T2 to T3, and the cooling rate is 30-35℃ / min;

[0011] The third stage is cooling, the temperature range is from T3 to T4, and the cooling rate is 25-30℃ / min;

[0012] T1=1035±50℃; T2=968℃±50℃; T3=593℃±50℃; T4=60±30℃;

[0013] Performing aging heat treatment on the product of the previous step;

[0014] Wherein, the chemical composition of the nickel-based high-temperature alloy workpiece is as follows: C: 0.02-0.1%, Mn≤0.1%, Si≤0.15%, P≤0.015%, S≤0.015%, Cr: 18-21%, Co: 12-15%, Mo: 3.5-5%, Ti: 2.75-3.25%, Al: 1.2-1.6%, Zr: 0.02-0.08%, B: 0.003-0.01%, Fe≤2%, Cu≤0.1%, Pb: ≤0.0005%, Bi≤0.00003%, Se≤0.0003%, Ag≤0.0005%, and the balance is Ni.

[0015] In some embodiments, T1 = 1035 ± 30°C; T2 = 968°C ± 30°C; T3 = 593°C ± 30°C; T4 = 60 ± 30°C.

[0016] In some embodiments, T1 = 1035 ± 10°C; T2 = 968°C ± 10°C; T3 = 593°C ± 10°C; T4 = 60 ± 10°C.

[0017] In some embodiments, the temperature of the stress relief heat treatment is 996±50° C. to 1010±50° C., and the holding time is 20-60 min.

[0018] In some embodiments, the temperature of the stress relief heat treatment is 996±10° C. to 1010±10° C., and the holding time is 30-35 min.

[0019] In some embodiments, the vacuum brazing temperature is T1, T1=1035±50° C., and the holding time is 1-20 min.

[0020] In some embodiments, the vacuum brazing temperature is T1, T1 = 1035 ± 10°C, and the holding time is 5-10 min.

[0021] In some embodiments, the aging heat treatment includes a first heat treatment and a second heat treatment performed sequentially.

[0022] The temperature of the first heat treatment is 843℃±50℃, and the holding time is 4h±30min;

[0023] The temperature of the second heat treatment is 760℃±50℃, and the holding time is 16h±30min.

[0024] In some embodiments, the aging heat treatment includes a first heat treatment and a second heat treatment performed sequentially.

[0025] The temperature of the first heat treatment is 843℃±10℃, and the holding time is 4h±10min;

[0026] The temperature of the second heat treatment is 760℃±10℃, and the holding time is 16h±10min.

[0027] In some embodiments, the cooling method used in the first stage of cooling includes static cooling in a vacuum furnace.

[0028] In some embodiments, the cooling method used in the second stage of cooling includes introducing argon gas into the vacuum furnace for cooling.

[0029] In some embodiments, the cooling method used in the third stage of cooling includes introducing argon gas into the vacuum furnace for cooling accompanied by air cooling.

[0030] In some embodiments, the nickel-based high-temperature alloy product obtained by the hot working method has one or more of the following properties:

[0031] The endurance performance at 732°C as tested according to ASTM E 292 is 50 hours or more (e.g., 50 to 55 hours, e.g., 50 to 60 hours);

[0032] A room temperature tensile strength of 1300 MPa or greater (e.g., 1300-1350 MPa, e.g., 1300-1400 MPa) as tested in accordance with ASTM E8 / E8M;

[0033] The room temperature yield strength measured according to ASTM E8 / E8M is 900 MPa or more (eg, 900-950 MPa, such as 900-1000 MPa).

[0034] In some aspects, the present disclosure provides a hot-working product of a nickel-based high-temperature alloy workpiece, obtained by any of the hot working methods described above.

[0035] Explanation of terms

[0036] If the following terms are used in this application, they may have the following meanings:

[0037] The term "vacuum brazing" refers to a material joining method in which the base metal is heated to a temperature below the melting point of the base metal and above the melting point of the brazing filler metal in a vacuum environment. The liquid brazing filler metal wets the surface or gaps of the base metal, spreads, fills the gaps through capillary flow, and ultimately solidifies and crystallizes, achieving atomic bonding. Vacuum brazing is a type of furnace brazing, performed in a vacuum furnace (or chamber). During vacuum brazing, the weldment is placed in a vacuum chamber, maintaining a vacuum level of no more than 0.04 Pa.

[0038] The term "heat treatment" refers to a metal thermal processing process in which a material is heated, kept warm, and cooled in a solid state to obtain the desired structure and properties.

[0039] Beneficial effects

[0040] This application adopts a specific heat treatment process to braze nickel-based high-temperature alloy workpieces. The specific process of this application effectively improves the microstructure of the workpiece, obtains a reasonable γ' phase morphology distribution, and thereby improves one or more properties of the brazed product.

[0041] One or more solutions of this application have one or more of the following beneficial effects:

[0042] (1) Brazed products have improved durability;

[0043] (2) Brazed products have improved room temperature tensile strength;

[0044] (3) The brazed product has improved room temperature yield strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 are scanning electron microscope images of nickel-based high-temperature alloy workpiece products according to some embodiments. DETAILED DESCRIPTION

[0046] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. Unless otherwise specified, parts, ratios, and percentages are all based on weight. In the examples, if specific conditions are not specified, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0047] A GH4738 high-temperature alloy workpiece (forging) is provided, whose chemical composition is as follows: C: 0.02-0.1%, Mn≤0.1%, Si≤0.15%, P≤0.015%, S≤0.015%, Cr: 18-21%, Co: 12-15%, Mo: 3.5-5%, Ti: 2.75-3.25%, Al: 1.2-1.6%, Zr: 0.02-0.08%, B: 0.003-0.01%, Fe≤2%, Cu≤0.1%, Pb: ≤0.0005%, Bi≤0.00003%, Se≤0.0003%, Ag≤0.0005%, and the balance is Ni.

[0048] The size specification of GH4738 high temperature alloy workpiece is 90mm×20mm×20mm.

[0049] Example 1

[0050] 1. In a vacuum furnace, perform stress relief heat treatment on the workpiece at a stress relief temperature of 996°C ± 10°C and a holding time of 30 minutes.

[0051] 2. In a vacuum furnace, vacuum braze the workpiece at a temperature of 1035°C ± 10°C and a holding time of 5 minutes.

[0052] 3. After the insulation is completed, the workpiece is cooled in sections as follows:

[0053] a) The first stage of cooling is in the range of (1035-968)°C ± 10°C, furnace cooling, and a cooling rate of 16°C / min;

[0054] b) The second stage of cooling is in the range of (968-593)°C ± 10°C, with argon gas for rapid cooling at a cooling rate of 25°C / min;

[0055] c) The third stage of cooling is in the range of (593-60)°C ± 10°C, with argon filling and fan fast cooling at a cooling rate of 30°C / min.

[0056] 4. In a vacuum furnace, perform standard aging heat treatment on the workpiece. The aging heat treatment includes two heat treatments. The first heat treatment temperature is 843℃ and the holding time is 4h±10min. The second heat treatment temperature is 760℃ and the holding time is 16h±10min.

[0057] 5. After being taken out of the furnace, GH4738 alloy brazing products are obtained.

[0058] Example 2

[0059] 1. In a vacuum furnace, perform stress relief heat treatment on the workpiece at a stress relief temperature of 1010°C ± 10°C and a holding time of 35 minutes.

[0060] 2. In a vacuum furnace, vacuum braze the workpiece at a temperature of 1035°C ± 10°C and a holding time of 5 minutes.

[0061] 3. After the insulation is completed, the workpiece is cooled in sections as follows:

[0062] a) The first stage of cooling is in the range of (1035-968)°C ± 10°C, furnace cooling, and a cooling rate of 20°C / min;

[0063] b) The second stage of cooling is in the range of (968-593)°C ± 10°C, with argon gas for rapid cooling at a cooling rate of 30°C / min;

[0064] c) The third stage of cooling is in the range of (593-60)°C ± 10°C, with argon filling and fan fast cooling at a cooling rate of 35°C / min.

[0065] 4. In a vacuum furnace, perform standard aging heat treatment on the workpiece. The aging heat treatment includes two heat treatments. The first heat treatment temperature is 843℃ and the holding time is 4h±10min. The second heat treatment temperature is 760℃ and the holding time is 16h±10min.

[0066] 5. After being taken out of the furnace, GH4738 alloy brazing products are obtained.

[0067] Analysis and testing

[0068] 1. Microscopic morphology analysis

[0069] The microstructure of the GH4738 alloy brazing product of Example 1 is shown in FIG. Figure 1 . Figure 1 The primary and secondary γ' phases can be observed, with the secondary γ' phase being dispersed. A reasonable morphological distribution of the γ' phase is beneficial for improving the durability of the product.

[0070] The metallographic structure of Example 2 is similar to that of Example 1.

[0071] 2. Mechanical properties analysis

[0072] The GH4738 alloy workpiece (forging) before hot working and the GH4738 alloy brazing products after hot working in Examples 1-2 (two samples for each example) were tested for high temperature rupture properties at 732°C and room temperature tensile properties according to ASTM E 292 and ASTM E8 / E8M, respectively. The test results are shown in Table 1.

[0073] Table 1

[0074]

[0075]

[0076] As shown in Table 1, the room temperature tensile properties, yield properties, and high temperature endurance of the brazed products are all higher than the AMS5707 standard value requirements for forgings and are comparable to the measured properties of forgings, indicating that the heat treatment method of the present invention can solve the problem of attenuation of tensile and endurance properties of GH4738 alloy after brazing.

[0077] Although the embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and variations may be made to the details in light of all the teachings disclosed herein, and that such modifications are within the scope of the present invention. The full scope of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. A method for thermal processing of a nickel-based high-temperature alloy workpiece, comprising: Perform stress relief heat treatment on nickel-based high-temperature alloy workpieces; Perform vacuum brazing on the product from the previous step; The product of the previous step is subjected to a staged cooling process, wherein the staged cooling process comprises: In the first stage, the temperature range is less than or equal to T1 to greater than T2, and the cooling rate is 16-20℃ / min; The second stage is cooling, the temperature range is less than or equal to T2 to greater than T3, and the cooling rate is 30-35℃ / min; The third stage is cooling, the temperature range is less than or equal to T3 to greater than or equal to T4, and the cooling rate is 25-30℃ / min; T1=1085℃; T2=968℃; T3=593℃; T4=60℃; Performing aging heat treatment on the product of the previous step; Wherein, the chemical composition of the nickel-based high-temperature alloy workpiece is as follows: C: 0.02-0.1%, Mn≤0.1%, Si≤0.15%, P≤0.015%, S≤0.015%, Cr: 18-21%, Co: 12-15%, Mo: 3.5-5%, Ti: 2.75-3.25%, Al: 1.2-1.6%, Zr: 0.02-0.08%, B: 0.003-0.01%, Fe≤2%, Cu≤0.1%, Pb: ≤0.0005%, Bi≤0.00003%, Se≤0.0003%, Ag≤0.0005%, and the balance is Ni.

2. The method according to claim 1, wherein T1＝1035℃。 3. The method according to claim 1, wherein T1＝1065℃。 4. The method according to claim 1, wherein The temperature of the stress relief heat treatment is 916°C to 1060°C, and the holding time is 20-60 minutes.

5. The method according to claim 1, wherein The temperature of vacuum brazing is 1035℃±30℃, and the holding time is 1-20min.

6. The method according to claim 1, wherein The aging heat treatment includes a first heat treatment and a second heat treatment performed sequentially. The temperature of the first heat treatment is 843℃±50℃, and the holding time is 4h±30min; The temperature of the second heat treatment is 760℃±50℃, and the holding time is 16h±30min.

7. The method according to claim 1, wherein The aging heat treatment includes a first heat treatment and a second heat treatment performed sequentially. The temperature of the first heat treatment is 843℃±10℃, and the holding time is 4h±10min; The temperature of the second heat treatment is 760℃±10℃, and the holding time is 16h±10min.

8. The method according to claim 1, wherein The cooling method adopted in the first stage of cooling includes static cooling in a vacuum furnace.

9. The method according to claim 1, wherein The cooling method adopted in the second stage of cooling includes introducing argon gas into the vacuum furnace for cooling.

10. The method according to claim 1, wherein The cooling method adopted in the third stage of cooling includes introducing argon gas into the vacuum furnace for cooling accompanied by air cooling.

11. The hot working method according to claim 1, wherein the nickel-based high-temperature alloy product obtained by the hot working method has one or more of the following properties: The durability at 732℃ tested according to ASTM E 292 is over 50h. The room temperature tensile strength tested according to ASTM E8 / E8M is above 1300MPa; The room temperature yield strength tested according to ASTM E8 / E8M is above 900 MPa.

12. A hot-working product of a nickel-based high-temperature alloy workpiece, obtained by the hot-working method according to any one of claims 1 to 11.

Images