A method of inhibiting abnormal grain growth in gh6783 alloy

Abstract

The present application belongs to the technical field of high-temperature alloy heat treatment, and relates to a method for inhibiting abnormal grain growth of GH6783 alloy. The method comprises the following steps: step 1, determining the grain non-growth temperature of GH6783 alloy; step 2, placing the GH6783 alloy bar in the furnace when the temperature of the heat treatment furnace reaches the non-growth temperature, starting timing and heat preservation for a specified time A when the temperature in the furnace reaches the non-growth temperature again; and step 3, slowly cooling the GH6783 alloy bar with the furnace to the beta phase aging temperature, heat preservation for 8-10 hours, and furnace discharge and air cooling after heat preservation. The present application can significantly inhibit the abnormal grain growth phenomenon of the GH6783 alloy bar after solid solution heat treatment, and improve the uniformity of the GH6783 alloy.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy heat treatment technology, and relates to a method for suppressing abnormal grain growth in GH6783 alloy. Background Technology

[0002] GH6783 alloy (foreign designation IN783) is a fourth-generation low-expansion high-temperature alloy with high strength and oxidation resistance. Its coefficient of thermal expansion is about 20% lower than that of IN718 alloy, and its density is the lowest among existing high-temperature alloys (7.81 g / cm³). 3 Due to the high Al content in the alloy, a unique β phase (BCC, NiAl phase) precipitates both within the grains and at the grain boundaries in the GH6783 alloy. The β phase can improve the alloy's resistance to stress-accelerated grain boundary oxidation, giving the alloy excellent oxidation resistance, structural stability, and high-temperature creep endurance.

[0003] However, during solution heat treatment, GH6783 alloy exhibits abnormal grain growth, with some grains even exceeding grade 2, leading to non-compliance in grain size testing of the bars upon delivery. Furthermore, the uneven grain size also affects the material's microstructure's ability to deform collaboratively, causing unstable fluctuations in mechanical properties.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for suppressing abnormal grain growth in GH6783 alloy, which can significantly suppress the abnormal grain growth phenomenon that occurs in GH6783 alloy during solution heat treatment and improve the uniformity of microstructure.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for suppressing abnormal grain growth in GH6783 alloy specifically includes the following steps: Step 1: Determine the grain growth-free temperature of GH6783 alloy; Step 2: After the heat treatment furnace temperature reaches the non-growth temperature, place the GH6783 alloy bar in the furnace. After the furnace temperature reaches the non-growth temperature again, start timing and hold for a specified time A. Step 3: The GH6783 alloy bar is slowly cooled in the furnace to the β phase aging temperature and held for 8-10 hours. After the holding period, it is removed from the furnace and air-cooled.

[0007] Specifically, the method for determining the non-grain growth temperature of GH6783 alloy in step 1 is as follows: Step 1.1: Obtain a sample block from GH6783 alloy bar with an asphalt grain size of 6~9 and perform heat treatment at 1000~1100℃ for 1±0.25h, and air cooling; define 6 temperature points in this heat treatment process as T1, T2...T6, with an interval of 20℃ between adjacent temperature points; Step 1.2: After grinding and polishing the sample block, perform chemical etching and observe whether the grain size increases: If at T m No grain growth occurred during temperature holding at T temperature, and at T... m+1 Grain growth occurs at a specific temperature point, thus determining T. m The temperature at which grains do not grow is denoted as m = 1, 2, 3, 4, 5, 6.

[0008] Specifically, in step 2, the specified time A is determined based on the specifications of the GH6783 alloy bar, as follows: the specification of the GH6783 alloy bar is defined as Φ. If 50 ≤ Φ < 200 mm, A = 0.75 × Φ, in min; If 200≤Φ<300mm, A =1×Φ, in min.

[0009] Furthermore, if the GH6783 alloy bar has a diameter Φ ≥ 300mm, the heating method is stepped heating, and the corresponding holding strategy is as follows: hold at 200℃ below the non-growth temperature for 120~150min, then raise the temperature to the non-growth temperature at full power and hold for a specified time B, where B = 1.25 × Φ, in minutes. It should be noted that when the bar diameter Φ ≥ 300mm, the holding time can be adjusted according to actual needs, for example, 120min, 125min, 130min, 135min, 140min, 145min, 150min, etc., which will not be listed here.

[0010] The chemical composition and mass percentage of the GH6783 alloy rod are as follows: carbon ≤0.03%, manganese ≤0.50%, silicon ≤0.50%, phosphorus ≤0.015%, sulfur ≤0.005%, chromium 2.50%~3.50%, nickel 26.00%~30.00%, niobium 2.50%~3.50%, aluminum 5.00%~6.00%, boron 0.003%~0.012%, iron ≤24.00%~27.00%, titanium ≤0.40%, tantalum ≤0.05%, copper ≤0.50%, with the remainder being cobalt.

[0011] Furthermore, in step 3, the cooling rate is 40~60℃ / h.

[0012] Furthermore, in step 3, the β-phase aging temperature of the GH6783 alloy bar is 845℃.

[0013] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: First, the temperature is maintained at a level that prevents abnormal grain growth, with the holding time A dynamically adjusted according to the alloy bar specifications. This stage dissolves the γ′ phase and partially dissolves the β phase, providing space for dislocation movement and annihilation, thereby reducing the driving force for grain growth. Then, the alloy bar is furnace-cooled to the β phase aging temperature of 845°C and held for 8–10 hours, promoting the full precipitation of the β phase at the grain boundaries to effectively suppress grain growth during subsequent solution treatment. This invention achieves optimized control of grain size and microstructure uniformity in GH6783 alloy bars through synergistic control of phase dissolution, dislocation regulation, and β phase precipitation. Attached Figure Description

[0014] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0016] Figure 1 A flowchart of a method for suppressing abnormal grain growth in GH6783 alloy provided by the present invention; Figure 2 This is a microstructure diagram of the GH6783 alloy bar in Example 1 of the present invention; Figure 3 The image shows the microstructure of the GH6783 alloy grains after direct solution heat treatment in Comparative Example 1. Figure 4 This is a microstructure diagram of the GH6783 alloy bar in Example 2 of the present invention; Figure 5 The image shows the microstructure of the GH6783 alloy grains after direct solution heat treatment in Comparative Example 2. Figure 6 This is a microstructure diagram of the GH6783 alloy bar in Example 3 of the present invention; Figure 7 The image shows the microstructure of the GH6783 alloy grains after direct solution heat treatment in Comparative Example 3. Detailed Implementation

[0017] Exemplary embodiments will be described in detail below. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0018] This invention provides a method for suppressing abnormal grain growth in GH6783 alloy, specifically including the following steps: Step 1: Determine the grain growth-free temperature of GH6783 alloy; Step 2: After the heat treatment furnace temperature reaches the non-growth temperature, place the GH6783 alloy bar in the furnace. After the furnace temperature reaches the non-growth temperature again, start timing and hold for a specified time A. Step 3: The GH6783 alloy bar is slowly cooled in the furnace to the β phase aging temperature and held for 8-10 hours. After the holding period, it is removed from the furnace and air-cooled.

[0019] The chemical composition and mass percentage of GH6783 alloy bars are as follows: carbon ≤0.03%, manganese ≤0.50%, silicon ≤0.50%, phosphorus ≤0.015%, sulfur ≤0.005%, chromium 2.50%~3.50%, nickel 26.00%~30.00%, niobium 2.50%~3.50%, aluminum 5.00%~6.00%, boron 0.003%~0.012%, iron ≤24.00%~27.00%, titanium ≤0.40%, tantalum ≤0.05%, copper ≤0.50%, with the remainder being cobalt. Furthermore, the GH6783 alloy ingots are produced using a two-stage melting process combining vacuum induction melting and vacuum arc remelting. After homogenization and free forging, the grain size of the core, radius (R / 2), and edges of the bars is grade 6~9.

[0020] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0021] Example 1 This embodiment provides a method for suppressing abnormal grain growth in GH6783 alloy, specifically including the following steps: Step 1: Determine the grain-free growth temperature of GH6783 alloy, specifically: Step 1.1: Obtain a sample block from a GH6783 alloy bar (Φ180mm) with an asphalt grain size of grade 8 and perform heat treatment at 1000~1100℃ for 1 hour, followed by air cooling; define the heat treatment process as 6 temperature points: T1 (1000℃), T2 (1020℃), T3 (1040℃), T4 (1060℃), T5 (1080℃), and T6 (1100℃), with an interval of 20℃ between adjacent temperature points; Step 1.2: After grinding and polishing the sample block, chemical etching was performed to observe whether the grain size increased. It was found that the grains did not grow at T2 (1020℃) but grew at T3 (1040℃). Therefore, the 1020℃... o C is determined as the temperature at which grains do not grow.

[0022] It should be noted that the number of temperature points is determined based on the range of furnace temperature fluctuation. For example, in this embodiment, the range of furnace temperature fluctuation is ±8℃. In order to eliminate the data abnormality caused by furnace temperature fluctuation, this embodiment sets the interval between adjacent temperature points to 20℃, thus determining the number of temperature points to be 6.

[0023] Step 2: Once the heat treatment furnace temperature reaches 1020℃, place the GH6783 alloy bar in the furnace. After the furnace temperature reaches 1020℃ again, start timing and hold for a specified time A (A=135min). The specified time A is determined according to the specifications of the GH6783 alloy bar, as follows: Since 50≤Φ<200mm, A=0.75×180=135, the unit is min.

[0024] Step 3: The GH6783 alloy bar is slowly cooled in the furnace to the β phase aging temperature of 845℃ and then held at that temperature for 8 hours. After the holding period, it is removed from the furnace and air-cooled. The cooling rate used for slow cooling in the furnace is 40℃ / h.

[0025] The microstructure of the GH6783 alloy bar after solution heat treatment according to this embodiment is shown in the figure. Figure 2 .

[0026] Comparative Example 1 This comparative example employs a two-stage melting process combining vacuum induction melting and vacuum arc remelting. After homogenization and free forging, GH6783 alloy bars (Φ180mm) are obtained, which are then directly subjected to solution heat treatment. The resulting microstructure photographs are shown below. Figure 3 .

[0027] contrast Figures 2-3 It can be seen that, Figure 2 Some individual grains may reach the 1.5 level in size, resulting in poor overall uniformity of the microstructure. Figure 3 The grain size is uniform at level 6. The method provided by this invention is highly effective in suppressing abnormal grain growth during solution heat treatment.

[0028] Example 2 This embodiment provides a method for suppressing abnormal grain growth in GH6783 alloy, specifically including the following steps: Step 1: Determine the grain-free growth temperature of GH6783 alloy, specifically: Step 1.1: Obtain a sample block from a GH6783 alloy bar (Φ350mm) with an asphalt grain size of 6.5 and perform heat treatment at 1000~1100℃ for 1.25h, followed by air cooling; define the heat treatment process as 6 temperature points: T1 (1000℃), T2 (1020℃), T3 (1040℃), T4 (1060℃), T5 (1080℃), and T6 (1100℃), with an interval of 20℃ between adjacent temperature points; Step 1.2: After grinding and polishing the sample block, chemical etching was performed to observe whether the grain size increased. It was found that the grains did not grow at T2 (1080℃) but grew at T3 (1100℃). Therefore, the 1080℃... o C is determined as the temperature at which grains do not grow.

[0029] Step 2: Since the dimensions exceed 300mm, the heat treatment furnace needs to be heated to 880°C first. o C. After placing the bar in the heat treatment furnace, wait for it to be heated again to 880°C. o Start holding at temperature C for 120 minutes, then increase the temperature to 1080°C at full power. o Start the heat preservation process at point C, and keep it warm for a specified time B (B = 1.25 × 350 = 437.5 min), rounded up to 440 min.

[0030] Step 3: The GH6783 alloy bar is slowly cooled in the furnace to the β phase aging temperature of 845℃ and then held at that temperature for 10 hours. After the holding period, it is removed from the furnace and air-cooled. The cooling rate used for slow cooling in the furnace is 55℃ / h.

[0031] The microstructure of the GH6783 alloy bar after solution heat treatment according to this embodiment is shown in the figure. Figure 4 .

[0032] Comparative Example 2 This comparative example employs a two-stage melting process combining vacuum induction melting and vacuum arc remelting. After homogenization and free forging, GH6783 alloy bars (Φ350mm) are obtained, which are then directly subjected to solution heat treatment. The resulting microstructure photographs are shown below. Figure 5 .

[0033] contrast Figures 4-5 It can be seen that, Figure 4 Some individual grains may reach the level 2, and the overall uniformity of the microstructure is poor. Figure 5 The grain size is uniform at grade 7.5. After using the method provided by this invention, no abnormal grain growth will occur during solution heat treatment.

[0034] Example 3 This embodiment provides a method for suppressing abnormal grain growth in GH6783 alloy, specifically including the following steps: Step 1: Determine the grain-free growth temperature of GH6783 alloy, specifically: Step 1.1: Obtain a sample block from a GH6783 alloy bar (Φ250mm) with an asphalt grain size of 7.5 and perform heat treatment at 1000~1100℃ for 0.75h, followed by air cooling; define the heat treatment process as 6 temperature points: T1 (1000℃), T2 (1020℃), T3 (1040℃), T4 (1060℃), T5 (1080℃), and T6 (1100℃), with an interval of 20℃ between adjacent temperature points; Step 1.2: After grinding and polishing the sample block, chemical etching was performed to observe whether the grain size increased. It was found that the grains did not grow at T2 (1080℃) but grew at T3 (1100℃). Therefore, the 1080℃... o C is determined as the temperature at which grains do not grow.

[0035] Step 2: Once the heat treatment furnace temperature reaches 1080℃, place the GH6783 alloy bar in the furnace. After the furnace temperature reaches 1080℃ again, start timing and hold for a specified time A (A=250min). The specified time A is determined according to the specifications of the GH6783 alloy bar, as follows: Since 200≤Φ<300mm, A=1×250=250, the unit is min.

[0036] Step 3: The GH6783 alloy bar is slowly cooled in the furnace to the β phase aging temperature of 845℃ and then held at that temperature for 9 hours. After the holding period, it is removed from the furnace and air-cooled. The cooling rate used for slow cooling in the furnace is 50℃ / h.

[0037] The microstructure of the GH6783 alloy bar after solution heat treatment according to this embodiment is shown in the figure. Figure 6 .

[0038] Comparative Example 3 This comparative example employs a two-stage melting process combining vacuum induction melting and vacuum arc remelting. After homogenization and free forging, GH6783 alloy bars (Φ250mm) are obtained, which are then directly subjected to solution heat treatment. The resulting microstructure photographs are shown below. Figure 7 .

[0039] contrast Figures 6-7 It can be seen that, Figure 6 Some individual grains may reach the 1.5 level in size, resulting in poor overall uniformity of the microstructure. Figure 7 The grain size is uniform at level 6. After using the method provided by this invention, no abnormal grain growth will occur during solution heat treatment.

[0040] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0041] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for suppressing abnormal grain growth in GH6783 alloy, characterized in that, Specifically, the following steps are included: Step 1: Determine the grain growth-free temperature of GH6783 alloy; Step 2: When the temperature of the heat treatment furnace reaches the non-growth temperature, place the GH6783 alloy bar in the furnace. After the temperature inside the furnace reaches the non-growth temperature again, start timing and hold for a specified time A. Step 3: The GH6783 alloy bar is slowly cooled in the furnace to the β-phase aging temperature and then held at that temperature for 8-10 hours. After holding, it is removed from the furnace and air-cooled. Step 1, the specific method for determining the grain non-growth temperature of GH6783 alloy is as follows: Step 1.1: Obtain a sample block from GH6783 alloy bar with an asphalt grain size of 6~9 and perform heat treatment at 1000~1100℃ for 1±0.25h, and air cooling; define 6 temperature points in this heat treatment process as T1, T2...T6, with an interval of 20℃ between adjacent temperature points; Step 1.2: After grinding and polishing the sample block, perform chemical etching and observe whether the grain size increases: If at T m No grain growth occurred during temperature holding at T temperature, and at T... m+1 Grain growth occurs at a specific temperature point, thus determining T. m The temperature at which grains do not grow is m = 1, 2, 3, 4, 5, 6; Step 2: The specified time A is determined based on the specifications of the GH6783 alloy bar, specifically as follows: Define the specification of the GH6783 alloy bar as Φ. If 50 ≤ Φ < 200 mm, A = 0.75 × Φ, in min; If 200≤Φ<300mm, A =1×Φ, in min; If the specification of GH6783 alloy bar is Φ≥300mm, the heating method adopts stepped heating. The corresponding heat preservation strategy is: after holding at 200℃ for 120~150min below the non-growth temperature, the temperature is raised to the non-growth temperature at full power and held for a specified time B, where B = 1.25×Φ, and the unit is min.

2. The method for suppressing abnormal grain growth in GH6783 alloy according to claim 1, characterized in that, The chemical composition and mass percentage of the GH6783 alloy bar are as follows: carbon ≤0.03%, manganese ≤0.50%, silicon ≤0.50%, phosphorus ≤0.015%, sulfur ≤0.005%, chromium 2.50%~3.50%, nickel 26.00%~30.00%, niobium 2.50%~3.50%, aluminum 5.00%~6.00%, boron 0.003%~0.012%, iron ≤24.00%~27.00%, titanium ≤0.40%, tantalum ≤0.05%, copper ≤0.50%, with the remainder being cobalt.

3. The method for suppressing abnormal grain growth in GH6783 alloy according to claim 1, characterized in that, In step 3, the cooling rate is 40~60℃ / h.

4. The method for suppressing abnormal grain growth in GH6783 alloy according to claim 1, characterized in that, In step 3, the β phase aging temperature of the GH6783 alloy bar is 845℃.

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