A method for preparing a low-oxygen, high-density powder superalloy

Abstract

The application provides a preparation method of a low-oxygen high-density powder superalloy. The method comprises the following steps: performing deoxidation pretreatment on the surface of a master alloy rod by plasma in-situ bombardment, performing vacuum induction melting and argon atomization powder preparation in a specific process parameter range, performing powder surface gas desorption treatment on the powder after oxygen-free closed screening by low-temperature physical desorption and medium-temperature chemical desorption, performing powder packaging by using oxygen-free and seamless packaging, and obtaining a low-oxygen high-density powder superalloy blank by low-temperature pretreatment and high-temperature high-pressure hot isostatic pressing sintering. The application can effectively control the original particle boundary and hole defects, improve the performance of the powder superalloy, and guarantee the development of the powder superalloy disc parts for advanced military and civil aviation engines in China.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy, specifically a method for preparing low-oxygen, high-density powder high-temperature alloys. Background Technology

[0002] Powder metallurgy superalloys are widely used in the development of key hot-end components such as turbine disks for advanced aero-engines. Currently, four generations of powder metallurgy superalloys have been successfully developed both domestically and internationally: the first generation includes 650℃ high-strength powder metallurgy superalloys such as René95, IN100, and FGH95; the second generation includes 750℃ damage-tolerant powder metallurgy superalloys such as René88DT, RR1000, and FGH96; the third generation includes high-strength damage-tolerant powder metallurgy superalloys such as René104 and FGH99; and the fourth generation includes creep-resistant powder metallurgy superalloys such as René130 and FGH101. With the continuous improvement of engine thrust-to-weight ratio and power-to-weight ratio, higher requirements are placed on turbine disk performance and defect control. To meet usage requirements, third- and fourth-generation powder superalloys incorporate more alloying elements, but exhibit higher gas sensitivity. Among these, oxygen content is closely related to the original particle boundary defects, while argon content directly affects the alloy density. Therefore, it is necessary to customize the process design based on the compositional characteristics of third- and fourth-generation powder superalloys to prepare low-oxygen, high-density powder superalloys that meet the development requirements of powder superalloy turbine disks for fifth-generation and above military and civilian engines. Summary of the Invention

[0003] The purpose of this invention This invention provides a method for preparing low-oxygen, high-density powder superalloys. Through a process design involving deoxidation pretreatment of the master alloy bar, argon atomization powder preparation, oxygen-free sealed sieving, gradient desorption and degassing, oxygen-free encapsulation, and hot isostatic pressing sintering, the entire process of preparing the powder superalloy billet achieves low-oxygen or oxidation-free treatment. Simultaneously, it reduces argon entrainment during atomization powder preparation and avoids gas leakage during degassing encapsulation and hot isostatic pressing, thereby reducing the argon content of the powder and alloy billet. This results in the preparation of low-oxygen, high-density powder superalloys, improving the performance of third- and fourth-generation powder superalloys and ensuring the development of advanced powder superalloy discs for military and civilian aero-engines in my country.

[0004] The technical solution of this invention is: The main sources of oxygen content in the powder superalloys of this invention are: oxygen adsorbed on the surface of the master alloy bar and inherited by the subsequent alloy melt and powder; insufficient vacuum in the powder smelting and atomization processes, leading to air leakage and oxygen enrichment; the atomization process significantly increases the specific surface area of ​​the alloy, making it highly susceptible to reaction with oxygen in the atomizing gas, resulting in oxygen enrichment; atmospheric sieving causing oxygen absorption on the powder surface; insufficient vacuum in the degassing and cladding processes, leading to air leakage and oxygen enrichment, or the degassing process failing to adequately remove oxygen. The main factors affecting the density of the powder superalloys are: during the atomization powdering stage, molten droplets are entrained by atomizing gas, forming hollow powder after solidification; insufficient removal of surface-adsorbed gas during the powder degassing process; inadequate cladding sealing, resulting in air leakage; and gas infiltration through cladding cracking during hot isostatic pressing sintering. Therefore, to achieve low-oxygen, high-density powder superalloy preparation, the following technical approaches are mainly adopted: A method for preparing low-oxygen, high-density powder superalloy is provided, characterized by comprising the following steps: Step 1: Deoxidation pretreatment is performed on the master alloy bar stock; Step 2: After remelting the master alloy bar, atomize it into powder using high-purity argon gas; Step 3: The obtained powder is sieved in a high-purity argon atmosphere (oxygen-free closed sieve). Step 4: The powder obtained after sieving is subjected to low-temperature physical desorption in a vacuum environment, followed by medium-temperature chemical desorption. Step 5: Encapsulate the powder in a sleeve made of oxygen-free seamless stainless steel.

[0005] Step 6: Perform hot isostatic pressing sintering on the encapsulated casing to obtain a low-oxygen, high-density powder high-temperature alloy billet.

[0006] Furthermore, in step 1, the master alloy ingot is processed into bars, and the oxide scale, oil stains and adsorbed water vapor on the surface of the bars are removed by plasma in-situ bombardment process in a closed vacuum environment.

[0007] Furthermore, in step 5, the packaging undergoes a vacuum cryogenic degassing treatment before being filled with powder. Even further, the degassing process is as follows: vacuum pressure ≤ 1.0 × 10⁻⁶. -3 Pa, keep warm at 150℃~250℃ for 2h~4h; Furthermore, in step 5, the encapsulation of the sleeve is achieved using seamless welding.

[0008] Furthermore, in step 6, the hot isostatic pressing (HIP) sintering process includes low-temperature pretreatment to eliminate residual gas in the cladding. The powder is then fully compacted under high temperature and high pressure.

[0009] Furthermore, the high-purity argon gas in steps 2 and 3 has a purity of ≥99.999% and an oxygen content of ≤1.0ppm.

[0010] Furthermore, the parameters for the in-situ plasma bombardment process are: vacuum pressure ≤ 1.0 × 10⁻⁶. -2 Pa, plasma power of 30kW~50kW, bombardment time of 10min~30min, bombardment temperature ≤200℃.

[0011] Furthermore, in step 2, during the atomization powdering process: the master alloy bar is heated under a vacuum pressure ≤1.0 Pa in the melting chamber during the melting stage. This avoids oxidation of the master alloy bar surface and subsequent oxygenation of the melt.

[0012] Furthermore, in step 2, the atomization powder preparation process involves the following steps: during the atomization stage, the melt superheat is 250℃~300℃, the metal flow rate is ≤5.0kg / min, and the atomization pressure is 4.0MPa~5.0MPa. This ensures the powder has good sphericity and a low hollow powder content, specifically, a powder sphericity ≥0.95 and a hollow powder content ≤1.0%.

[0013] Furthermore, in step 3, the screening criterion is to select powder particles with a particle size range of 10μm to 53μm.

[0014] Furthermore, the physical desorption and degassing process parameters are: vacuum pressure ≤ 1.0 × 10⁻⁶. -3 Pa, temperature 110℃~150℃, hold for 2h~4h to remove water vapor and physically adsorbed gases from the powder surface.

[0015] Furthermore, the chemical desorption and degassing process parameters are: vacuum pressure ≤ 1.0 × 10⁻⁶. -3 Pa, temperature 650℃~850℃, hold for 2h~4h to remove chemically adsorbed gases from the powder surface.

[0016] Furthermore, in step 5, the process parameters for powder filling are: vacuum pressure ≤ 1.0 × 10⁻⁶. -3 Pa, 300℃~500℃, vibration frequency 10Hz~30Hz, amplitude 1.0mm~3.0mm; Furthermore, the seamless welding employs an integrated visual electron beam welding device. Vibration is turned off during the welding process to maintain the original vacuum level and temperature. After welding is completed and cooled to room temperature, the sheath is removed.

[0017] Furthermore, the hot isostatic pressing process parameters are as follows: pretreatment at 800℃~1000℃ for 2h~4h to eliminate residual gas in the cladding, followed by holding at 1100℃~1200℃ and 130MPa~150MPa for 2h~8h to achieve powder sintering. The oxygen content of the powder high-temperature alloy is ≤50ppm, and the density is ≥99.9%.

[0018] Advantages of the present invention (1) Based on the characteristics of the composition of third and fourth generation powder high-temperature alloys, this invention achieves low-oxygen or non-oxidation treatment of the entire process of powder high-temperature alloy preparation by optimizing the atomization powder preparation process parameters, oxygen-free sealed sieving, gradient desorption and degassing, oxygen-free encapsulation and hot isostatic pressing sintering, etc., through the deoxidation pretreatment of the master alloy bar, optimization of atomization powder preparation process parameters, and customized design of oxygen-free sealed sieving, gradient desorption and degassing, oxygen-free encapsulation and hot isostatic pressing sintering. This significantly reduces the oxygen and argon content of powder and alloy blanks, eliminates the original particle boundary defects, and reduces the porosity between powders and internal pores, thereby preparing low-oxygen, high-density powder high-temperature alloys, ensuring the high performance, high density and high reliability of powder high-temperature alloy discs.

[0019] (2) The process design of the present invention makes up for the technical shortcomings in the preparation process of third and fourth generation powder high temperature alloys with low oxygen and high density in China, and provides key technical support for the development of advanced powder high temperature alloy disks for military and civilian aero engines in my country.

[0020] (3) The process design of the present invention can not only prepare low oxygen and high density powder high temperature alloy billets, but also produce high temperature alloy powder products with high sphericity, low oxygen and low hollow powder content, which can be used in fields such as 3D printing where powder quality requirements are high, and has good economic benefits and application value. Detailed Implementation

[0021] The examples disclosed will be described with reference to some (but not all) of the disclosed examples. In fact, many different examples may be described and these examples should not be construed as limited to those set forth herein. These examples are described so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0022] Example 1: The third-generation powder metallurgy high-temperature alloy master alloy ingot was processed into bars weighing approximately 50 kg each, and then subjected to a vacuum pressure of 8.7 × 10⁻⁶. -3 Under conditions of 180℃ and 35kW, plasma bombardment of the master alloy bar surface for 15 minutes was used to remove oxide scale, oil, and adsorbed moisture. The pre-treated master alloy bar was then placed in a melting crucible of an argon atomization powder-making furnace. The equipment was evacuated using a vacuum system, and the medium-frequency power supply was turned on to heat the master alloy bar when the vacuum pressure reached 0.63Pa. When the master alloy bar was completely melted and the temperature reached 1550℃, it was atomized using high-purity argon gas with a purity ≥99.999% and an oxygen content of 0.328ppm, at a metal flow rate of 4.6 kg / min and an atomization pressure of 4.5MPa. The prepared powder was collected and stored and transported using high-purity argon gas, followed by sieving in a high-purity argon protective atmosphere to obtain high-temperature alloy powder ranging from 10μm to 53μm. The degassing furnace was evacuated to a vacuum pressure of 5.4×10⁻⁶. -4Pa, the powder is placed in a degassing furnace and heated to 120℃ for 2 hours to remove moisture and physically adsorbed gases from the powder surface. The temperature is then increased to 800℃ and held for 2 hours to remove chemically adsorbed gases from the powder surface. A stainless steel sheath is placed in a sheathing machine, and a vacuum of 6.8 × 10⁻⁶ is applied. -4 The powder was heated to 200℃ and held for 2 hours, then heated to 450℃. A vibration source was turned on with a vibration frequency of 20Hz and an amplitude of 1.8mm. When the powder reached the cladding opening, the vibration source was turned off, maintaining the equipment vacuum and temperature. The electron beam welding switch was then turned on to seal the cladding opening. After the cladding cooled to room temperature, it was removed. The cladding filled with powder was placed in a hot isostatic pressing furnace and pre-treated at 800℃ for 4 hours to eliminate residual gas. The temperature was then increased to 1180℃, the pressure increased to 140MPa, and the furnace was held for 4 hours before removal.

[0023] The high-temperature alloy powder and billet were sampled and analyzed. The powder sphericity was 0.97, the hollow powder content was 0.82%, the oxygen content of the billet was 45 ppm, and the density was 99.97%.

[0024] Example 2: The fourth-generation powder metallurgy high-temperature alloy master alloy ingot was processed into bars weighing approximately 50 kg each, and then subjected to a vacuum pressure of 7.3 × 10⁻⁶. -3 Under conditions of 180℃ and 35kW, plasma bombardment of the master alloy bar surface for 15 minutes was used to remove oxide scale, oil, and adsorbed moisture. The pre-treated master alloy bar was then placed in a melting crucible of an argon atomization powder-making furnace. The equipment was evacuated using a vacuum system, and the medium-frequency power supply was turned on to heat the master alloy bar when the vacuum pressure reached 0.76Pa. When the master alloy bar was completely melted and the temperature reached 1580℃, it was atomized using high-purity argon gas with a purity ≥99.999% and an oxygen content of 0.275ppm, at a metal flow rate of 4.2 kg / min and an atomization pressure of 4.3MPa. The prepared powder was collected and stored and transported under high-purity argon gas, followed by sieving in a high-purity argon protective atmosphere to obtain high-temperature alloy powders ranging from 10μm to 53μm. The degassing furnace was evacuated to a vacuum pressure of 6.2×10⁻⁶. -4 Pa, the powder is placed in a degassing furnace and heated to 120℃ for 2 hours to remove moisture and physically adsorbed gases from the powder surface. The temperature is then increased to 750℃ and held for 2 hours to remove chemically adsorbed gases from the powder surface. A stainless steel sheath is placed in a sheathing machine, and a vacuum of 8.6 × 10⁻⁶ is applied. -4a. Heat to 200℃ and hold for 2 hours, then heat to 450℃ and turn on the vibration source at a frequency of 20Hz and an amplitude of 1.8mm. When the powder reaches the cladding opening, turn off the vibration source, maintain the vacuum and temperature of the equipment, and turn on the electron beam welding switch to seal the cladding opening. After the cladding cools to room temperature, remove it. Place the cladding filled with powder in a hot isostatic pressing furnace, heat to 800℃ and hold for 4 hours for pretreatment to eliminate residual gas in the cladding, then heat to 1180℃, pressurize to 140MPa, hold for 4 hours, and then remove from the furnace.

[0025] The high-temperature alloy powder and billet were sampled and analyzed. The powder sphericity was 0.96, the hollow powder content was 0.94%, the oxygen content of the billet was 48 ppm, and the density was 99.98%.

[0026] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0027] Descriptions of various advantageous arrangements have been shown for illustrative and descriptive purposes, but such descriptions are not intended to be exclusive or limited to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different advantageous examples may describe different advantages compared to other advantageous examples. One or more examples have been selected and described in order to best illustrate the principles and practical application of the examples, and to enable those skilled in the art to understand that this disclosure contains various examples with various modifications suitable for the particular intended use.

Claims

1. A method for preparing a low-oxygen, high-density powder superalloy, characterized in that, Includes the following steps: Step 1: Perform deoxidation pretreatment on the master alloy bar stock; Step 2: After remelting the master alloy bar, atomize it into powder using high-purity argon gas; Step 3: The obtained powder is sieved in a high-purity argon atmosphere (oxygen-free closed sieve). Step 4: The powder obtained after sieving is subjected to low-temperature physical desorption in a vacuum environment, followed by medium-temperature chemical desorption. Step 5: Encapsulate the powder in a sleeve made of oxygen-free seamless stainless steel. Step 6: Perform hot isostatic pressing sintering on the encapsulated casing to obtain a low-oxygen, high-density powder high-temperature alloy billet.

2. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: In step 1, the master alloy ingot is processed into bars, and the oxide scale, oil stains and adsorbed water vapor on the surface of the bars are removed by plasma in-situ bombardment process in a closed vacuum environment.

3. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: In step 5, the packaging undergoes vacuum cryogenic degassing before powder filling. Furthermore, the degassing process is as follows: vacuum pressure ≤ 1.0 × 10⁻⁶. -3 Pa, keep warm at 150℃~250℃ for 2h~4h.

4. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: In step 5, the encapsulation of the sleeve is achieved by seamless welding.

5. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: In step 6, the hot isostatic pressing sintering process includes low-temperature pretreatment to eliminate residual gas in the cladding.

6. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: The high-purity argon gas used in steps 2 and 3 has a purity ≥ 99.999% and an oxygen content ≤ 1.0 ppm. Furthermore, the parameters for the in-situ plasma bombardment process are: vacuum pressure ≤ 1.0 × 10⁻⁶. -2 Pa, plasma power of 30kW~50kW, bombardment time of 10min~30min, bombardment temperature ≤200℃.

7. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: In step 2, the atomization powder production process involves heating the master alloy bar under a vacuum pressure ≤1.0 Pa in the melting chamber during the smelting stage. Further, in step 2, the atomization powder production process involves a melt superheat of 250℃~300℃, a metal flow rate ≤5.0 kg / min, and an atomization pressure of 4.0 MPa~5.0 MPa during the atomization stage.

8. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: In step 3, the screening criterion is to select powder particles with a particle size range of 10μm to 53μm.

9. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: The physical desorption and degassing process parameters are: vacuum pressure ≤ 1.0 × 10⁻⁶. -3 The powder is heated to 110℃~150℃ for 2h~4h to remove moisture and physically adsorbed gases from its surface. The chemical desorption and degassing process parameters are: vacuum pressure ≤1.0×10⁻⁶ Pa. -3 Pa, temperature 650℃~850℃, hold for 2h~4h to remove chemically adsorbed gases from the powder surface.

10. The method for preparing a low-oxygen, high-density powder superalloy as described in claim 1, characterized in that: In step 5, the process parameters for powder filling are: vacuum pressure ≤ 1.0 × 10⁻⁶. -3 Pa, 300℃~500℃, vibration frequency 10Hz~30Hz, amplitude 1.0mm~3.0mm.