A thermomechanical treatment method for optimizing creep properties of GH4169 alloy

Abstract

The invention discloses a thermomechanical treatment method for optimizing the creep properties of a GH4169 alloy. The method comprises the following steps: step 1: performing a solution treatment on the GH4169 alloy, wherein the solution treatment temperature is higher than the carbide precipitation temperature in the GH4169 alloy, and is around T1=960°C, ranging from -5°C to 5°C, and the holding time is t1=(d×0.6+30)min to (d×0.6+70)min, where d is the cross-sectional area of ​​the GH4169 alloy sample, in mm; step 2: applying a rolling deformation of 10% to the solution-treated GH4169 alloy, and the rolling temperature is room temperature; step 3: raising the furnace temperature to 1050°C, placing the cold-rolled GH4169 alloy in the furnace, and holding the furnace temperature for 20-30 min after the furnace temperature stabilizes; and step 4: taking out the GH4169 alloy and quenching it in water, wherein the quenching temperature is 10-25°C. This invention optimizes the alloy's grain boundary structure through a combined cold rolling and heat treatment process, significantly improving the high-temperature creep performance of the GH4169 alloy. This method is characterized by a short cold rolling and heat treatment process and a significant improvement in creep performance.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature alloys, and in particular to a thermomechanical treatment method for optimizing the creep properties of a GH4169 alloy. Background Art

[0002] Superalloys are a class of metallic materials based on Fe, Ni, and Co, capable of long-term operation at temperatures of 600°C and above under certain stresses. They exhibit excellent resistance to oxidation, corrosion, and fatigue, making them indispensable in the energy and chemical industries, equipment manufacturing, and defense sectors. While there are numerous types of superalloys, nickel-based superalloys are the most widely used and have the widest application. For example, key aircraft engine components such as combustion chambers, turbine blades, and even turbochargers are often made of nickel-based superalloys. Ni-based superalloys can be categorized as either solid solution-strengthened or precipitation-strengthened, depending on the strengthening method. GH4169 alloy (Inconel 718 alloy) is a Ni-based superalloy strengthened by precipitation strengthening of body-centered tetragonal γ" and face-centered cubic γ′ phases. It exhibits excellent comprehensive properties within the temperature range of -253 to 700°C. Its yield strength below 650°C ranks first among deformable superalloys. It also exhibits excellent fatigue, radiation, oxidation, and corrosion resistance, as well as excellent machinability, weldability, and long-term structural stability. Consequently, GH4169 alloy is currently the most widely used superalloy and is often referred to as the "King of Superalloys."

[0003] As aircraft engine thrust ratios increase, service conditions become increasingly demanding, placing higher demands on the alloy's high-temperature creep and fatigue resistance, as well as its high-temperature oxidation resistance. Currently, alloying is the primary method for optimizing the performance of GH4169 alloy. For example, the journal article "Deformation twinning during high-temperature compression tests of the Ni-base superalloy ATI 718Plus®" (ActaMaterialia, 2022, 225: 115743) reports that by adjusting the Ti / Al atomic ratio in the alloy, the γ′ phase content and phase stability were increased, resulting in the Allvac® 718Plus™ alloy, which successfully raised its reliable service temperature to above 700°C. The journal article "Microstructure and mechanical properties of additive-manufactured Inconel 718 alloy strengthened by oxide dispersion with 0.3 wt% Sc addition" (Journal of Alloys and Compounds, 2022, 918: 165763) reports that adding a small amount of the rare earth element Sc to the GH4169 alloy effectively improves the room-temperature and high-temperature tensile properties of the alloy. While alloying can improve the alloy's high-temperature service performance, it can also increase material costs and make recycling more difficult.

[0004] With the progress of global industrialization, the sustainable development of materials has received increasing attention from scientists around the world. Therefore, exploring low-cost, environmentally friendly methods to improve the high-temperature comprehensive properties of GH4169 alloy, especially its high-temperature creep performance, has become a scientific issue that needs to be addressed urgently. Summary of the Invention

[0005] To address the technical challenges presented by the aforementioned background technology, the present invention provides a thermomechanical treatment method for optimizing the creep properties of GH4169 alloy. By combining cold rolling with heat treatment, the alloy's grain boundary structure is optimized, significantly enhancing the high-temperature creep properties of the alloy. This method is characterized by a short cold rolling and heat treatment time and a significant improvement in creep properties.

[0006] Specifically, the present invention provides a thermomechanical treatment method for optimizing the creep properties of GH4169 alloy, comprising the following steps:

[0007] Step 1: Solution treatment of the GH4169 alloy. The solution treatment temperature is higher than the carbide precipitation temperature of the GH4169 alloy, and is around T1 = 960 ° C, between -5 ° C and 5 ° C, and the holding time is t1 = (d × 0.6 + 30) min to (d × 0.6 + 70) min, where d is the cross-sectional area of ​​the GH4169 alloy sample, in mm;

[0008] Step 2: Apply 10% rolling deformation to the solution treated GH4169 alloy at room temperature;

[0009] Step 3: Raise the furnace temperature to 1050°C, put in the cold-rolled GH4169 alloy, and keep it warm for 20-30 minutes after the furnace temperature stabilizes;

[0010] Step 4: Take out the GH4169 alloy and quench it in water at a quenching temperature of 10 to 25°C.

[0011] As a further illustration of the present invention, in step 1, during the solution treatment, the machined GH4169 alloy sample (the sample is machined into a specified size to meet the furnace requirements and ensure uniform heating of the sample) is placed in a box-type resistance furnace, and refractory bricks are placed at the bottom of the GH4169 alloy sample. The thickness of the refractory bricks is such that the GH4169 alloy sample is located in the middle of the furnace.

[0012] As a further illustration of the present invention, in step 1, during the solution treatment, after the furnace temperature rises to the target solution treatment temperature, the GH4169 alloy sample is placed in the furnace, and the timing is started after the furnace temperature stabilizes.

[0013] As a further illustration of the present invention, in step 1, the temperature is raised to 500°C at a rate of 10°C / min, then to 800°C at a rate of 5°C / min, and then to the target solution treatment temperature at a rate of 3°C / min.

[0014] As a further illustration of the present invention, in step 1, after the holding time of the solution treatment is reached, the GH4169 alloy sample is immediately taken out from the heat treatment furnace and quenched in water at a quenching water temperature of 10° C. to 25° C.

[0015] As a further illustration of the present invention, the temperature raising method in step 3 is: raising the temperature to 500°C at a rate of 10°C / min, then raising the temperature to 800°C at a rate of 5°C / min, and then raising the temperature to 1050°C at a rate of 3°C / min.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] This invention provides a thermomechanical treatment method for optimizing the creep properties of GH4169 alloy. By combining cold rolling with heat treatment, the alloy's grain boundary structure is optimized, significantly enhancing the alloy's high-temperature creep properties. This method is characterized by a short cold rolling and heat treatment time and a significant improvement in creep properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 (a) is the microstructure of the GH4169 alloy after solution treatment and aging treatment in Example 1 of the present invention; Figure 1 (b) is the microstructure of the GH4169 alloy after solution treatment, thermomechanical treatment, and aging treatment in Example 1 of the present invention; the red lines represent coincident lattice grain boundaries (CSLs), and the black lines represent non-coincident lattice grain boundaries.

[0019] Figure 2 1 and 2 are creep time-strain curves of the GH4169 alloy after solution treatment + aging treatment and the GH4169 alloy after solution treatment + thermomechanical treatment + aging treatment under 650°C / 700MPa working conditions in Example 1 of the present invention.

[0020] Figure 3 (a) is the microstructure of the GH4169 alloy after solution treatment and aging treatment in Example 2 of the present invention; Figure 3 (b) is the microstructure of the GH4169 alloy after solution treatment, thermomechanical treatment, and aging treatment in Example 2 of the present invention; the red lines represent coincident lattice grain boundaries (CSLs), and the black lines represent non-coincident lattice grain boundaries.

[0021] Figure 4 These are the creep time-strain curves of the GH4169 alloy after solution + aging treatment and the GH4169 alloy after solution + thermomechanical treatment + aging treatment in Example 2 of the present invention under 650°C / 750MPa working conditions. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Example 1

[0024] A thermomechanical treatment method for optimizing creep properties of GH4169 alloy comprises the following steps:

[0025] S1: Solution treatment of GH4169 alloy was performed at 960℃ for 1h.

[0026] S2: 10% rolling deformation is applied to the GH4169 alloy after solution treatment, and the rolling temperature is room temperature.

[0027] S3: Raise the furnace temperature to 1050℃, put in the cold-rolled GH4169 alloy, and keep it warm for 20 minutes after the furnace temperature stabilizes.

[0028] S4: Take out the GH4169 alloy and quench it in water at a quenching temperature of 10 ~ 25℃.

[0029] like Figure 1 As shown in (a), the microstructure of GH4169 alloy after solution + aging treatment is composed of equiaxed grains with a grain size of about 170μm. The red line represents the CSL grain boundary, and its volume fraction is 34.3%. Figure 1 As shown in (b), the microstructure of the GH4169 alloy after solution treatment + thermomechanical treatment + aging treatment is still composed of equiaxed grains with a grain size of about 162 μm, but the volume fraction of CSL grain boundaries is greatly increased to 55%.

[0030] like Figure 2 As shown in Figure 2, the creep life of GH4169 alloy at 650°C / 700 MPa after solution and aging treatment is 173 h. After thermomechanical treatment, the creep life increases to 385 h, an increase of over 200%. This is because the primary creep mechanism in GH4169 alloy during high-temperature creep is grain boundary sliding. Compared to non-coincident lattice grain boundaries, coincident lattice grain boundaries (CSLs) have lower Gibbs free energy and greater stability, resulting in lower slip rates during high-temperature creep. Therefore, increasing the volume fraction of CSL grain boundaries through thermomechanical treatment can effectively improve the alloy's creep performance.

[0031] Example 2

[0032] A thermomechanical treatment method for optimizing creep properties of GH4169 alloy comprises the following steps:

[0033] S1: Solution treatment of GH4169 alloy at 965℃ for 1h

[0034] S2: 10% rolling deformation is applied to the GH4169 alloy after solution treatment, and the rolling temperature is room temperature.

[0035] S3: Raise the furnace temperature to 1050℃, put in the cold-rolled GH4169 alloy, and keep it warm for 30 minutes after the furnace temperature stabilizes.

[0036] S4: Take out the GH4169 alloy and quench it in water at a quenching temperature of 10 ~ 25℃.

[0037] like Figure 3 As shown in (a), the microstructure of GH4169 alloy after solution + aging treatment is composed of equiaxed grains with a grain size of about 170μm. The red line represents the CSL grain boundary, and its volume fraction is 34.3%. Figure 3 As shown in (b), the microstructure of the GH4169 alloy after solution treatment + thermomechanical treatment + aging treatment is still composed of equiaxed grains with a grain size of about 171 μm, but the volume fraction of CSL grain boundaries is greatly increased to 56%.

[0038] like Figure 4 As shown in the figure, the creep life of GH4169 alloy after solution + aging treatment at 650℃ / 750MPa is 32h. After the introduction of thermomechanical treatment, the creep life is increased to 105h, an increase of more than 300%.

[0039] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0040] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A thermomechanical treatment method for optimizing creep properties of GH4169 alloy, characterized in that: The following steps are involved: Step 1: Solution treatment of the GH4169 alloy at a temperature higher than the carbide precipitation temperature of the GH4169 alloy, at T1 = 960°C ± 5°C, and a holding time of t1 = (d × 0.6 + 30) min to (d × 0.6 + 70) min, where d is the cross-sectional diameter of the GH4169 alloy sample, in mm; Step 2: Apply 10% rolling deformation to the solution treated GH4169 alloy at room temperature; Step 3: Raise the furnace temperature to 1050℃, put in the cold-rolled GH4169 alloy, and keep it warm for 20-30 minutes after the furnace temperature stabilizes; Step 4: Take out the GH4169 alloy and quench it in water at a quenching temperature of 10°C to 25°C.

2. The thermomechanical treatment method for optimizing creep properties of GH4169 alloy according to claim 1, characterized in that: In step 1, during the solution treatment, the machined GH4169 alloy sample is placed in a box-type resistance furnace, and refractory bricks are placed at the bottom of the GH4169 alloy sample. The thickness of the refractory bricks is based on ensuring that the GH4169 alloy sample is located in the middle of the furnace.

3. The thermomechanical treatment method for optimizing creep properties of GH4169 alloy according to claim 1, characterized in that: In step 1, during the solution treatment, after the furnace temperature rises to the target solution treatment temperature, the GH4169 alloy sample is placed in the furnace, and the timing starts after the furnace temperature stabilizes.

4. The thermomechanical treatment method for optimizing creep properties of GH4169 alloy according to claim 3, characterized in that: In step 1, the temperature is raised to 500°C at a rate of 10°C / min, then to 800°C at a rate of 5°C / min, and then to the target solution treatment temperature at a rate of 3°C / min.

5. The thermomechanical treatment method for optimizing creep properties of GH4169 alloy according to claim 1, characterized in that: In step 1, after the holding time of the solution treatment is reached, the GH4169 alloy sample is immediately taken out from the heat treatment furnace and quenched in water at a quenching water temperature of 10° C. to 25° C.

6. The thermomechanical treatment method for optimizing creep properties of GH4169 alloy according to claim 1, characterized in that: The heating method in step 3 is: heating to 500°C at a rate of 10°C / min, then heating to 800°C at a rate of 5°C / min, and then heating to 1050°C at a rate of 3°C / min.

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