A preparation method, a part and an application of a low-cost small and medium-sized GH4698 alloy part

Abstract

The application belongs to the field of high-temperature alloy powder metallurgy, and particularly discloses a preparation method of low-cost small and medium-sized GH4698 alloy parts, the parts and application, the preparation method comprises the following steps: first, providing specific GH4698 alloy spherical powder; then, rapidly cooling at 30-50 DEG C / s after hot isostatic pressing at 1155-1185 DEG C and 180-200 MPa for 4.5-6 h; finally, performing two-stage aging treatment to obtain the GH4698 alloy parts. Through the powder metallurgy near-net forming technology, the material utilization is greatly improved, the manufacturing cost is reduced, and through the optimized heat treatment process, the bimodal distribution of the gamma' strengthening phase is obtained, so that the parts have excellent mechanical properties at 750 DEG C: tensile strength > 900 MPa, yield strength > 700 MPa, elongation > 6%, and reduction of area > 9%, and are suitable for manufacturing key components such as an aero-engine drum shaft and a compressor disc.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-temperature alloy powder metallurgy, and particularly relates to a preparation method of low-cost small and medium-sized GH4698 alloy parts, the parts and application. BACKGROUND

[0002] Nickel-based high-temperature alloys have an irreplaceable position in the fields of high-end equipment such as aerospace, energy and nuclear power due to their excellent high-temperature mechanical properties, good oxidation resistance and hot corrosion resistance. Among them, GH4698 alloy, as a typical Ni-Cr-based precipitation strengthened high-temperature alloy, has a service temperature of 750-800 DEG C and is widely used in key components such as drum shafts and compressor discs of aircraft engines which bear heavy load and have long service life requirements.

[0003] At present, small and medium-sized GH4698 alloy parts (such as drum shafts with a radial size of usually between 250mm and 400mm) for aircraft engines are mainly prepared by the process of "vacuum induction melting + vacuum consumable remelting (or electroslag remelting)", and then the alloy rod is formed into a forged blank through multi-fire forging, and finally the final part is obtained through mechanical processing. However, the traditional process route has the following problems in the actual preparation of small and medium-sized GH4698 alloy parts:

[0004] First, the material utilization rate is extremely low: due to the difficulty of realizing the "near net shape" blank similar to the shape of the final part by the forging process, the machining allowance is large, and the material is wasted seriously. Taking a typical GH4698 drum shaft for an engine as an example, the weight of the finished product is only about 22kg, while the initial forging blank is as high as about 210kg, and the material utilization rate is only 10.4%, which not only causes a huge waste of valuable metal resources, but also significantly increases the manufacturing cost;

[0005] Second, the microstructure and performance of the forged part have obvious directional differences: during the forging process, due to the uneven distribution of strain field, temperature field and stress field of the rod in the transverse and longitudinal directions, the microstructure of the forging blank in different directions is different, which further causes the inconsistency of the mechanical properties in the longitudinal and transverse directions. In addition, the drum shaft itself has a complex structure, and the shape and size of each part are different, which causes different strain and stress states during the forging process, further aggravating the dispersion of the mechanical properties of each region of the final part, affecting the overall reliability and service safety of the part;

[0006] Third, the existing standard heat treatment process is complex and extremely long: according to the record in the Handbook of China High Temperature Alloy, the standard heat treatment system of GH4698 alloy is: 1100℃-1120℃x8h / air cooling +1000℃±10℃x4h / air cooling +775℃±10℃x16h / air cooling. The process needs to be operated three times of furnace loading and furnace discharging, and needs to strictly control the heating rate, set multiple stages of holding to ensure uniform heating and avoid deformation, and the whole heat treatment cycle is as long as about 68h, resulting in high energy consumption and low production efficiency. In addition, due to the uneven distribution of dislocation density in each region of the forging blank, abnormal grain growth is easily caused during the solution treatment, which causes the deformation of grain boundary and grain to be inconsistent, thereby deteriorating the comprehensive performance of the alloy.

[0007] In summary, the existing preparation process of small and medium-sized GH4698 alloy parts based on forging generally has the problems of low material utilization rate, obvious directional property of microstructure and performance, high energy consumption and long cycle of heat treatment, and difficulty in ensuring the consistency of performance of each part. Therefore, it is urgent to develop a new preparation technology that can realize near-net forming, uniform performance and efficient process to meet the increasing reliability and economy requirements of key components of aero-engine.

[0008] Therefore, the present application is proposed. SUMMARY

[0009] The present application aims to overcome the shortcomings of the prior art, and provides a preparation method of low-cost small and medium-sized GH4698 alloy parts, parts and applications, which are mainly used to solve the problems of low material utilization rate, mechanical property directionality dispersion and poor consistency, complex heat treatment process and long time consumption, and difficulty in controlling the uniformity of microstructure in the prior art.

[0010] The purpose of the present application is solved by the following technical scheme:

[0011] In a first aspect, the present application provides a preparation method of low-cost small and medium-sized GH4698 alloy parts, which comprises the following steps:

[0012] Step 1, providing a specific GH4698 alloy spherical powder;

[0013] Step 2, hot isostatic pressing the GH4698 alloy spherical powder, and then rapidly cooling to obtain a GH4698 alloy blank;

[0014] Step 3, two-stage aging treatment is performed on the GH4698 alloy blank to obtain the GH4698 alloy part.

[0015] Further, the particle size of the GH4698 alloy spherical powder is 15-50μm.

[0016] Further, the GH4698 alloy spherical powder is prepared by a plasma rotating electrode method, and the sphericity of the GH4698 alloy spherical powder is >98%, and the hollow powder rate is <0.05%.

[0017] Further, in step 2, the process parameters of the hot isostatic pressing treatment are as follows: the temperature is 1155-1185°C, which can be 1155°C, 1165°C, 1175°C, 1185°C, etc., and can be set according to actual needs; the pressure is 180-200 MPa, which can be 180 MPa, 185 MPa, 190 MPa, 200 MPa, etc., and can be set according to actual needs; and the holding time is 4.5-6 h, which can be 4.5 h, 4.8 h, 5.5 h, 6 h, etc., and can be set according to actual needs. This step realizes the densification and metallurgical bonding between powder particles by precisely controlling the temperature, pressure and holding time of the hot isostatic pressing, and at the same time makes the γ' strengthening phase fully solid-solute in the matrix at high temperature, thereby providing organizational conditions for the uniform precipitation of the γ' phase in the subsequent aging treatment.

[0018] Further, in step 2, the cooling rate of the rapid cooling is 30-50°C / s, which can be 30°C / s, 36°C / s, 45°C / s, 50°C / s, etc., and can be set according to actual needs. By controlling the cooling speed of the hot isostatic pressing blank, the premature precipitation and excessive growth of the γ' phase are inhibited, thereby forming a fine and uniform γ' phase initial organization in the matrix, which lays an organizational foundation for the controlled ripening, size optimization and spherical morphology optimization of the γ' phase in the subsequent two-stage aging treatment process.

[0019] Further, in step 3, the two-stage aging treatment includes:

[0020] First-stage aging: heating to 980-1010°C, which can be 980°C, 990°C, 1000°C, 1010°C, etc., and can be set according to actual needs; holding for 2-4 h, which can be 2 h, 2.5 h, 3.5 h, 4 h, etc., and can be set according to actual needs; and then air cooling to room temperature at a wind speed of 3-5 m / s, which can be 3 m / s, 3.5 m / s, 4.5 m / s, 5 m / s, etc., and can be set according to actual needs;

[0021] Second stage aging: heating to 765 DEG C to 785 DEG C, can be 765 DEG C, 775 DEG C, 785 DEG C, etc., can be set according to actual demand specifically;10h to 16h can be 10h, 12h, 14h, 16h, etc., can be set according to actual demand specifically;Then air cooling to room temperature at 3m / s to 5m / s wind speed, can be 3m / s, 3.5m / s, 4.5m / s, 5m / s, etc., can be set according to actual demand specifically.The step is through accurate control of the temperature of two-stage aging, holding time and cooling rate, promotes the formation of γ' strengthening phase with bimodal size distribution and regular spherical morphology in the alloy, realizes the good matching of strength and plasticity.

[0022] In a second aspect, the application further provides a low-cost medium and small-sized GH4698 alloy piece, which is prepared by the preparation method described above, and the mechanical properties of the GH4698 alloy piece under the condition of 750 DEG C satisfy that the tensile strength is greater than 900MPa, the yield strength is greater than 700MPa, the elongation is greater than 6%, and the reduction of area is greater than 9%.

[0023] In a third aspect, the application further provides an application of the low-cost medium and small-sized GH4698 alloy piece in the field of aerospace engine, and the GH4698 alloy piece is specifically used for manufacturing a drum shaft or a compressor disc of an aero-engine.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] The technical scheme provided by the application achieves significant progress in material utilization rate, microstructure performance and process efficiency through powder metallurgy process innovation and parameter optimization, and the specific manifestations are as follows:

[0026] (1) Material utilization rate is greatly improved, and the uniformity of the organization is obviously improved: the material utilization rate of traditional forging process is only about 10% due to the inability to realize near-net forming, and there is obvious difference in the direction of the organization. The GH4698 alloy spherical powder (particle size 15-50 μm, sphericity > 98%, hollow powder rate < 0.05%) meeting the requirements is prepared by the plasma rotating electrode method, which is beneficial to the full filling of the powder in the sleeve during the powder loading process due to the high sphericity and better flowability of the fine particle size powder; at the same time, the hollow powder rate is lower, which can reduce the micro size deformation of the alloy parts during high temperature service, and is beneficial to the safety of the alloy high temperature service. Combined with the precisely controlled hot isostatic pressing process (1155-1185℃, 180-200 MPa, 4.5-6 h), not only the full metallurgical bonding between the powder particles is realized, but also the material utilization rate is improved to more than 85%, which greatly reduces the manufacturing cost. At the same time, the method fundamentally eliminates the organization direction difference caused by the uneven distribution of strain field and temperature field in traditional forging, and ensures the consistency of the organization and mechanical properties of the parts.

[0027] (2) The heat treatment process is optimized, and the control of the strengthening phase is more accurate: the two-stage aging treatment is adopted instead of the traditional three-stage heat treatment in the present application: the first stage aging (980-1010℃, 2-4 h, air cooling) promotes the growth and ripening of the fine γ' phase in the hot isostatic pressing blank under the action of Ostwald ripening mechanism, and forms a larger size γ' phase, because the first stage aging temperature is high, and the diffusion rate of alloying elements is fast, which provides the thermodynamic and kinetic conditions for the growth and ripening of γ' phase; the second stage aging (765-785℃, 10-16 h, air cooling) promotes the analysis of γ' phase, and forms a fine size γ' phase, because the second stage aging temperature is lower, and the diffusion ability of alloying elements is weaker, which has little effect on the large size γ' phase precipitated in the first stage aging during the process of promoting the analysis of γ' phase; finally, the γ' strengthening phase with double peak distribution of γ' phase size is obtained. The process greatly improves the production efficiency, shortens the heat treatment period from about 68 h of the traditional process to less than 40 h, and only needs two furnace loading operations, and the rapid cooling (30-50℃ / s) after hot isostatic pressing effectively inhibits the premature precipitation and excessive growth of γ' phase, provides an ideal initial organization for the aging treatment, and makes the final γ' phase have a regular near-spherical morphology and an optimized size distribution.

[0028] (3) The prepared GH4698 alloy parts have excellent comprehensive performance: the GH4698 alloy parts obtained by the present application still have excellent mechanical properties at 750℃: the tensile strength is > 900 MPa, the yield strength is > 700 MPa, the elongation is > 6%, and the reduction of area is > 9%, which fully meets the use requirements of key components of aero-engine.

[0029] In summary, the present application solves the technical problems of low material utilization rate, poor microstructure uniformity and low heat treatment efficiency of the traditional forging process by optimizing the whole process of the powder metallurgy process. The present application significantly improves the mechanical properties of small and medium-sized GH4698 alloy parts while greatly reducing the manufacturing cost, and finally provides a preparation scheme with better performance, more stable quality and lower cost for key components of aerospace engines (such as drum shaft and compressor disc). BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate the principles of the application, and, together with the description, serve to explain the application.

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0032] Figure 1 Flow chart of the preparation method of the low-cost small and medium-sized GH4698 alloy parts of the present application;

[0033] Figure 2 Comparison chart of the heat treatment process of the GH4698 alloy blank of the present application and the standard heat treatment process of the traditional GH4698 alloy blank;

[0034] Figure 3 Microstructure chart of the grain size characteristics of the GH4698 high-pressure turbine drum shaft part obtained in Example 1 of the present application;

[0035] Figure 4 Microstructure chart of the γ' phase of the GH4698 alloy blank after hot isostatic pressing in Example 1 of the present application;

[0036] Figure 5 Microstructure chart of the γ' phase of the GH4698 high-pressure turbine drum shaft part obtained in Example 1 of the present application. DETAILED DESCRIPTION

[0037] Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. In the following description, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all the embodiments consistent with the present application. Rather, they are merely examples consistent with some aspects of the present application, as detailed in the appended claims.

[0038] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the accompanying drawings and examples. Example 1

[0039] Reference Figure 1 The present example provides a preparation method of a low-cost small and medium-sized GH4698 high-pressure turbine drum shaft (the radial size is about φ300mm), which specifically comprises the following steps:

[0040] Step 1: GH4698 alloy spherical powder is prepared by a plasma rotating electrode method, and powder with a particle size in the range of 15μm-50μm is selected by sieving. It is detected that the sphericity of the GH4698 alloy spherical powder reaches 98.9%, and the hollow powder rate is 0.01%.

[0041] Step 2: The above-mentioned GH4698 alloy spherical powder is loaded into a prefabricated sheath, after vacuumizing and sealing, it is placed in a hot isostatic pressing device for densification treatment. The specific process parameters are: temperature 1185℃, pressure 180MPa, holding time 5h; after the treatment is completed, the blank is rapidly cooled at a cooling rate of about 50℃ / s, and a dense GH4698 alloy blank is obtained.

[0042] Step 3: The GH4698 alloy blank obtained by hot isostatic pressing is subjected to two-stage aging treatment, and then machined to obtain a GH4698 high-pressure turbine drum shaft product meeting the requirements of the design drawing.

[0043] The two-stage aging treatment comprises:

[0044] First-stage aging: the GH4698 alloy blank is heated to 1010℃, and then air-cooled to room temperature at a wind speed of 5m / s;

[0045] Second-stage aging: the blank treated by the first-stage aging is heated to 765℃, and then air-cooled to room temperature at a wind speed of 5m / s.

[0046] In order to verify the technical effect of the present application, the inventors observed the microstructure of the alloy during the preparation process: the grain size characteristic microstructure diagram of the GH4698 high-pressure turbine drum shaft product obtained in the present example is shown in Figure 3 From Figure 3 It can be seen that the GH4698 high-pressure turbine drum shaft product prepared by the present application presents uniform equiaxed crystal characteristics, and there is no mixed crystal phenomenon, and the grain size grade is 7; the γ' phase microstructure of the GH4698 alloy blank after hot isostatic pressing in the present example is shown in Figure 4 From Figure 4It can be seen that the γ′ phase in the GH4698 alloy billet exhibits uniform, fine, and nearly spherical characteristics; the microstructure of the γ′ phase in the GH4698 high-pressure turbine drum shaft component obtained in this embodiment is shown in the figure below. Figure 5 As shown, from Figure 5 It can be seen that the γ′ phase in the GH4698 high-pressure turbine drum shaft part prepared by the present invention exhibits a near-spherical morphology with two size characteristics, wherein the average size of the large-size γ′ phase is 226 nm and the average size of the small-size γ′ phase is 43 nm. Example 2

[0047] This embodiment provides a low-cost, small-to-medium-sized GH4698 booster stage drum (radial dimension approximately φ250mm), specifically including the following steps:

[0048] Step 1: GH4698 alloy spherical powder was prepared using the plasma rotating electrode method, and powder with a particle size in the range of 15μm to 50μm was selected by sieving. The sphericity of the GH4698 alloy spherical powder was found to be 99.1%, and the hollow powder rate was 0.02%.

[0049] Step 2: The above-mentioned GH4698 alloy spherical powder is loaded into a pre-made sleeve, vacuumed and sealed, and then placed in a hot isostatic pressing (HIP) apparatus for densification treatment. The specific process parameters are: temperature 1155℃, pressure 200MPa, and holding time 6h; after the treatment, the billet is rapidly cooled at a cooling rate of approximately 40℃ / s to obtain a dense GH4698 alloy billet.

[0050] Step 3: Perform two-stage aging treatment on the GH4698 alloy billet obtained by hot isostatic pressing, and then machine it to obtain the GH4698 booster stage drum part that meets the design drawings.

[0051] The two-level timeliness processing includes:

[0052] First stage of aging: Heat the GH4698 alloy billet to 980℃, hold for 4 hours, and then air cool to room temperature at a wind speed of 3m / s;

[0053] Second stage aging: The billet treated with the first stage aging is heated to 785℃ and held for 16 hours, and then cooled to room temperature with a wind speed of 5m / s. Example 3

[0054] refer to Figure 1 This embodiment provides a low-cost method for manufacturing a small to medium-sized GH4698 compressor drum (radial dimension approximately φ400mm), specifically including the following steps:

[0055] Step 1, the GH4698 alloy spherical powder is prepared by the plasma rotating electrode method, and the powder with a particle size in the range of 15 μm-50 μm is selected by screening. The sphericity of the GH4698 alloy spherical powder reaches 99.2%, and the hollow powder rate is 0.01%.

[0056] Step 2, the above-mentioned GH4698 alloy spherical powder is loaded into a prefabricated can, after vacuumizing and sealing, and is placed in a hot isostatic pressing device for densification treatment. The specific process parameters are: temperature 1170℃, pressure 190MPa, holding time 5h; after the treatment is completed, the blank is rapidly cooled at a cooling rate of about 45℃ / s to obtain a dense GH4698 alloy blank.

[0057] Step 3, the GH4698 alloy blank obtained by hot isostatic pressing is subjected to two-stage aging treatment, and then is machined to obtain a GH4698 low-pressure compressor drum part meeting the requirements of the design drawing.

[0058] The two-stage aging treatment includes:

[0059] First-stage aging: the GH4698 alloy blank is heated to 995℃, and then is air-cooled to room temperature at a wind speed of 4m / s;

[0060] Second-stage aging: the blank treated by the first-stage aging is heated to 775℃, and then is air-cooled to room temperature at a wind speed of 4m / s. Example 4

[0061] The embodiment provides a preparation method of a low-cost small and medium-sized GH4698 low-pressure compressor drum (the radial size is about φ350mm), and specifically includes the following steps:

[0062] Step 1, the GH4698 alloy spherical powder is prepared by the plasma rotating electrode method, and the powder with a particle size in the range of 15 μm-50 μm is selected by screening. The sphericity of the GH4698 alloy spherical powder reaches 99.0%, and the hollow powder rate is 0.02%.

[0063] Step 2, the above-mentioned GH4698 alloy spherical powder is loaded into a prefabricated can, after vacuumizing and sealing, and is placed in a hot isostatic pressing device for densification treatment. The specific process parameters are: temperature 1165℃, pressure 180MPa, holding time 6h; after the treatment is completed, the blank is rapidly cooled at a cooling rate of about 35℃ / s to obtain a dense GH4698 alloy blank.

[0064] Step 3, the GH4698 alloy blank obtained by hot isostatic pressing is subjected to two-stage aging treatment, and then is machined to obtain a GH4698 low-pressure compressor drum part meeting the requirements of the design drawing.

[0065] The two-stage aging treatment comprises:

[0066] The first-stage aging treatment comprises: heating the GH4698 alloy blank to 1000℃, holding for 3h, and then air cooling to room temperature at a wind speed of 3.5m / s;

[0067] The second-stage aging treatment comprises: heating the blank subjected to the first-stage aging treatment to 785℃, holding for 12h, and then air cooling to room temperature at a wind speed of 4.5m / s.

[0068] Further, in order to fully verify the beneficial effects of the present application, the GH4698 alloy parts prepared in Examples 1 to 4 were subjected to high-temperature tensile property tests at 750℃ according to the GB / T 228.2 standard, and the specific test results are shown in Table 1:

[0069] Table 1: Mechanical property test results of the GH4698 alloy parts in Examples 1 to 4

[0070]

[0071] As can be seen from Table 1, the tensile strength of the GH4698 alloy parts prepared in Examples 1 to 4 is higher than 900MPa, the yield strength is higher than 700MPa, the elongation is greater than 6%, and the reduction of area is greater than 9% under the condition of 750℃ high temperature. Compared with the relevant technical standards, the results show that the high-temperature tensile strength and plasticity of the GH4698 alloy parts prepared by the powder metallurgy forming method provided by the present application meet the technical index requirements.

[0072] In summary, the GH4698 alloy parts prepared by the present application have excellent strength and plasticity at 750℃, and the higher strength index helps to improve the service safety and reliability of the parts. In addition, as shown in Table 1, the total time of the heat treatment process provided by the present application is significantly shortened, only less than 40h, while the traditional standard heat treatment usually needs about 68h, which greatly improves the production efficiency and reduces the manufacturing cost while ensuring excellent performance. Figure 2

[0073] The above description is only a specific implementation of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application.

[0074] It should be understood that the present application is not limited to the above described and that various modifications and changes can be made without departing from the scope thereof. The scope of the present application is limited only by the claims appended hereto.​

Claims

1. A method for preparing low-cost, small to medium-sized GH4698 alloy parts, characterized in that, The preparation method includes the following steps: Step 1: Provide GH4698 alloy spherical powder; the particle size of the GH4698 alloy spherical powder is 15μm to 50μm, the GH4698 alloy spherical powder is prepared by plasma rotating electrode method, and the sphericity of the GH4698 alloy spherical powder is >98%, and the hollow powder rate is <0.05%; Step 2: The GH4698 alloy spherical powder is subjected to hot isostatic pressing, followed by rapid cooling to obtain GH4698 alloy billet; the process parameters for hot isostatic pressing are: temperature 1155℃~1185℃, pressure 180MPa~200MPa, holding time 4.5h~6h; the cooling rate for rapid cooling is 30℃ / s~50℃ / s. Step 3: Perform a two-stage aging treatment on the GH4698 alloy billet to obtain the GH4698 alloy part; the two-stage aging treatment includes: First-level aging: Heat to 980℃~1010℃, keep warm for 2h~4h, then air cool to room temperature at a wind speed of 3m / s~5m / s; Second-stage aging: Heat to 765℃~785℃, keep warm for 10h~16h, then air cool to room temperature at a wind speed of 3m / s~5m / s.

2. A small to medium-sized GH4698 alloy part, characterized in that, The GH4698 alloy component is prepared by the preparation method described in claim 1.

3. The small and medium-sized GH4698 alloy parts according to claim 2, characterized in that, The mechanical properties of the GH4698 alloy parts at 750℃ meet the following requirements: tensile strength > 900MPa, yield strength > 700MPa, elongation > 6%, and reduction of area > 9%.

4. An application of a small to medium-sized GH4698 alloy component as described in claim 2 or 3 in the field of aerospace engines.

5. The application according to claim 4, characterized in that, The GH4698 alloy parts are specifically used to manufacture drum shafts or compressor discs for aero engines.

Images