A method for preparing Mo-Cu alloy powder

Abstract

This invention relates to a method for preparing Mo-Cu alloy powder. The method involves mixing molybdenum powder and copper powder, deoxidizing them, and then fabricating a pre-alloy rod using a spark plasma sintering process. The pre-alloy rod is then powdered using a plasma rotating electrode atomization process. Specifically, the method includes: selecting molybdenum powder and copper powder with a particle size less than 50 μm, mixing them uniformly, and treating them in a hydrogen atmosphere to remove oxygen; completing the Mo-Cu pre-alloying process through spark plasma sintering; connecting the threaded end of the resulting pre-alloy rod to the spindle of a plasma rotating electrode atomization device, and powdering under an argon atmosphere; placing the prepared powder into a spark plasma sintering machine to obtain the pre-alloy rod, and then further powdering it to obtain molybdenum-copper composite powder. The advantages are: the molybdenum-copper composite powder obtained by this method has high sphericity, low oxygen content, and uniform distribution of the molybdenum-copper alloy; the method allows for adjustment of the molybdenum and copper alloy ratio, and the shorter sintering time avoids copper leakage.

Description

Technical Field

[0001] This invention pertains to methods for producing molybdenum-copper materials, and particularly relates to a method for preparing Mo-Cu alloy powder by combining SPS and PREP methods. Background Art

[0002] Molybdenum-copper alloy is an alloy composed of metallic molybdenum and copper. Due to its excellent breaking ability, thermal and electrical conductivity, non-magnetic properties, low and variable coefficient of thermal expansion, high compressive strength, resistance to welding, and superior mechanical properties, it is widely used in sealing materials for vacuum electronic devices and laser devices, as well as heat sink substrates in semiconductor devices. It also has extensive applications in the aerospace field.

[0003] In existing technologies, the main industrial method for producing molybdenum-copper alloys is the melt infiltration method. This involves first preparing a sintered molybdenum framework with a certain porosity, and then infiltrating molten copper into the pre-prepared framework. However, due to the poor wettability between molybdenum and copper, uneven copper distribution easily occurs, resulting in difficult processing and inconsistent performance of the molybdenum-infiltrated copper workpieces. If molybdenum-copper alloy powder is prepared, uniformly composed molybdenum-copper alloy workpieces can be produced through processes such as sintering.

[0004] The 2019 publication in *Xi'an University of Technology*, titled "Preparation and Performance Study of Mo-20wt%Cu Composite Material," authored by Sun Chenglin, describes a method for preparing precursor powder using a wet chemical process. The powder underwent drying, calcination, and a two-stage hydrogen reduction process. Vacuum pressureless sintering was then employed to investigate the relationship between temperature and the microstructure and metallographic uniformity of the Mo-Cu composite material. Patent application number CN201910517019.X discloses a method for preparing spherical molybdenum-copper powder by airflow agitation and spray drying, followed by sintering to obtain a high-density, uniformly structured molybdenum-copper alloy.

[0005] As can be seen from the above papers and patents, the key to the current molybdenum-copper alloy preparation method is to achieve a uniform distribution of molybdenum and copper. However, regardless of the melting infiltration method or the molybdenum-copper oxide co-reduction method, due to the large difference in melting points between the two phases of the molybdenum-copper alloy, a liquid phase will exist during the sintering process, making it difficult to control the uniform distribution of copper when the copper content is high. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing Mo-Cu alloy powder, thereby achieving the preparation of high copper content molybdenum-copper alloy, resulting in uniform distribution of molybdenum and copper phases, low oxygen content, high sintering density, and significantly reduced preparation costs.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A method for preparing Mo-Cu alloy powder involves mixing molybdenum powder and copper powder and deoxidizing them, then forming a pre-alloy rod through a spark plasma sintering process, and finally pulverizing the pre-alloy rod through a plasma rotating electrode atomization process.

[0009] The specific steps include:

[0010] 1) Pretreatment of copper powder and molybdenum powder

[0011] Molybdenum powder and copper powder with a particle size of less than 50μm are selected and mixed evenly in a powder mixer. The mixed powder is then treated with hydrogen atmosphere at a certain temperature range to remove oxygen.

[0012] 2) Preparation of Mo-Cu pre-alloying

[0013] Mo-Cu pre-alloying is completed by spark plasma sintering. The oxygen-de-oxidized mixed powder is filled into a graphite mold, the graphite mold is sealed, and then both ends of the graphite mold are brought into contact with the upper and lower electrodes of the spark plasma sintering machine. Under the set pressure and sintering temperature, the temperature is held for 30±5 minutes. After sintering is completed, the sintered body is taken out of the graphite mold and processed into a cylinder with a length of 150-180 mm and a diameter of 30 mm, with a thread processed at one end to obtain a pre-alloyed rod.

[0014] 3) Pre-preparation of Mo-Cu composite powder

[0015] Connect the threaded end of the pre-alloyed rod to the spindle of the plasma rotating electrode atomizing device. Then, evacuate the atomizing chamber of the plasma rotating electrode atomizing device and fill it with high-purity argon gas. When the pressure in the atomizing chamber is 0.06-0.1 MPa and the oxygen content in the atomizing chamber is <100 ppm, start the spindle to increase the rotation speed and start the arc current. After the powder making is completed, cool for 30±5 minutes and open the powder hopper to collect the powder.

[0016] 4) Preparation of Mo-Cu composite materials

[0017] The powder prepared in step 3) is placed in a spark plasma sintering machine, and step 2) is repeated to obtain a pre-alloyed rod. The pre-alloyed rod is then prepared into molybdenum-copper composite powder using the method in step 3).

[0018] The Mo-Cu alloy powder has a D50 < 50 μm, an oxygen content < 100 ppm, and a copper weight content ≤ 50%.

[0019] The specific temperature range mentioned in step 1) is 800~1050℃.

[0020] Step 2) The graphite mold is a cylindrical structure. After the oxygen-deoxygenated mixed powder is placed inside the graphite mold, graphite cylinders are placed at both ends of the graphite mold to seal it.

[0021] In step 2), the set pressure of the discharge plasma sintering machine should not exceed 5 kN, and the set sintering temperature should be 1080–1150 °C.

[0022] The surface runout of the sintered body described in step 2) along the circumferential direction of the cylinder shall not exceed 0.03 mm.

[0023] Step 3) The spindle speed of the plasma rotating electrode atomization device is 20,000 to 40,000 rpa / min, and the current is 500 to 700 A.

[0024] The operation in step 4) is performed more than twice.

[0025] The roughness of the pre-alloyed rod described in step 2) is not higher than 0.03 mm.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The preparation method of Mo-Cu alloy powder involves directly sintering molybdenum-copper alloy powder to prepare molybdenum-copper workpieces. Specifically, molybdenum powder and copper powder are first mixed and then subjected to spark plasma sintering (SPS) to obtain a pre-alloyed molybdenum-copper rod. Molybdenum-copper powder is then prepared using a plasma rotating electrode atomization (PREP) device. The powder prepared by this method exhibits high sphericity, low oxygen content, and uniform distribution of the molybdenum-copper alloy. Furthermore, this method allows for adjustment of the molybdenum and copper alloy ratio, and the shorter sintering time avoids copper leakage.

[0028] 2. The method of this invention combines SPS and PREP methods to prepare Mo-Cu alloy powder, which not only eliminates the long mechanical alloying process in the conventional preparation process, greatly saving time and cost, but also allows for controllable oxygen content in the composite powder without introducing impurities.

[0029] 3. This invention can prepare molybdenum-copper composite powder with a copper content of up to 50%, and can obtain molybdenum-copper powder with high copper content and uniform distribution of copper and molybdenum.

[0030] 4) This invention uses molybdenum and copper powder with a particle size of less than 50 μm. By controlling the PREP spindle speed and plasma power, powders with different particle size distribution ranges are prepared, resulting in a molybdenum-copper alloy particle size distribution range of 20–200 μm. Selecting molybdenum and copper powder with an initial particle size of less than 50 μm ensures uniform mixing of the molybdenum and copper, reducing process cycles.

[0031] 5) The molybdenum-copper alloy powder prepared by this invention has a high sphericity, which can be applied to application scenarios such as additive manufacturing where high sphericity is required. Detailed Implementation

[0032] The present invention will now be described in detail, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] The preparation method of Mo-20%Cu alloy powder includes the following steps and process conditions:

[0035] 1) Pretreatment of copper powder and molybdenum powder

[0036] Select molybdenum and copper powders with a particle size of less than 50 μm, mix them thoroughly in a mixer, then place the powder in an alumina crucible and introduce hydrogen gas, and keep it at 900°C for 2 hours to remove any oxygen that may be present in the powder.

[0037] 2) Preparation of Mo-Cu pre-alloying

[0038] The Mo-Cu pre-alloying was prepared in a graphite mold with an outer diameter of 60 mm, an inner diameter of 40 mm, and a height of 200 mm. The mold was a cylindrical, open-ended graphite mold with a cavity, with one end sealed by a cylindrical graphite column. The powder obtained in step 1) was loaded into the cavity, compacted, and the graphite mold was then sealed. The two ends of the graphite mold were then brought into contact with the upper and lower electrodes of an SPS sintering machine. During sintering, the pressure was set to 2 kN, and the temperature was increased from room temperature to 1100 °C at a rate of 5 °C / min, held for 30 min. After sintering, the sintered body was removed from the mold, and the sintered rod was machined into a cylinder 180 mm long and 30 mm in diameter, with an M25 thread at one end. The surface runout of the cylinder did not exceed 0.03 mm.

[0039] 3) Pre-preparation of Mo-Cu composite powder

[0040] Connect the threaded end of the pre-alloyed rod to the PREP spindle, then start the vacuum system to evacuate the atomization chamber. After evacuation, fill the atomization chamber with high-purity argon gas. Once the pressure in the atomization chamber reaches 0.06 MPa, open the oxygen content analysis valve. When the oxygen content analyzer reading is <100 ppm, start the spindle and gradually increase the speed to 30,000 rpm. Start the electric arc with an input power of 600 A. After the powdering is completed (when the alloy rod material is consumed to the end), cool for 30 minutes and open the powder hopper to collect the powder.

[0041] 4) Preparation of Mo-Cu composite materials

[0042] The alloy powder prepared in step 3) was placed into a graphite mold, and the sintering test in step 2) and the powder preparation test in step 3) were repeated. The prepared alloy material was then machined into a cylinder. The machined cylinder was then used to prepare molybdenum-copper composite powder by the PREP method.

[0043] Example 2

[0044] The preparation method of Mo-50%Cu alloy powder includes the following steps and process conditions:

[0045] 1) Pretreatment of copper powder and molybdenum powder

[0046] Due to the increased proportion of copper, smaller particle size powders were used to ensure complete mixing of molybdenum and copper powders. Molybdenum and copper powders with a particle size of less than 20 μm were selected and thoroughly mixed in a mixer. After that, the powders were placed in an alumina crucible and hydrogen gas was introduced. The mixture was kept at 950°C for 2 hours to remove any oxygen that may be present in the powders.

[0047] 2) Preparation of Mo-Cu pre-alloying

[0048] The Mo-Cu pre-alloying was prepared in a graphite mold with an outer diameter of 60 mm, an inner diameter of 40 mm, and a height of 200 mm. The mold was a cylindrical, cavity-type graphite mold with openings at both ends, with one end sealed by a cylindrical graphite column. The powder obtained in step 1) was loaded into the cavity, compacted, and the graphite mold was then sealed. The two ends of the graphite mold were then brought into contact with the upper and lower electrodes of the SPS sintering machine. Due to the high copper phase content, to prevent the molten copper from overflowing during sintering, the pressure was set to 1 kN, and the temperature was increased from room temperature to 1100°C at a rate of 5°C / min, held for 30 min. After sintering, the sintered body was removed from the mold, and the sintered rod was machined into a cylinder 180 mm long and 30 mm in diameter, with an M25 thread at one end. The surface runout of the cylinder did not exceed 0.03 mm.

[0049] 3) Pre-preparation of Mo-Cu composite powder

[0050] Connect the threaded end of the pre-alloyed rod to the PREP spindle, then start the vacuum system to evacuate the atomization chamber. After evacuation, fill the atomization chamber with high-purity argon gas. Once the pressure in the atomization chamber reaches 0.06 MPa, open the oxygen content analysis valve. When the oxygen content analyzer reading is <100 ppm, start the spindle and gradually increase the speed to 20,000 rpm. Start the electric arc with an input power of 500 A. After powder preparation is complete, cool for 30 minutes and open the powder hopper to collect the powder.

[0051] 4) Preparation of Mo-Cu composite materials

[0052] The alloy powder prepared in step 3) was placed into a graphite mold, and the sintering test in step 2) and the powder preparation test in step 3) were repeated. The prepared alloy material was machined into a cylindrical shape. Then, the machined cylindrical bar was used to prepare molybdenum-copper composite powder by PREP method.

[0053] Example 3

[0054] The preparation method of Mo-5%Cu alloy powder includes the following steps and process conditions:

[0055] 1) Pretreatment of copper powder and molybdenum powder

[0056] Select molybdenum and copper powders with a particle size of less than 50 μm, mix them thoroughly in a mixer, then place the powder in an alumina crucible and introduce hydrogen gas, and keep it at 900°C for 2 hours to remove any oxygen that may be present in the powder.

[0057] 2) The Mo-Cu pre-alloy was prepared in a graphite mold. The mold was a cylindrical graphite mold with cavities, open at both ends, with an outer diameter of 60 mm, an inner diameter of 40 mm, and a height of 200 mm. One end of the mold was sealed with a cylindrical graphite column. The powder obtained in step 1) was loaded into the cavity, compacted, and the graphite mold was sealed. Then, the two ends of the graphite mold were brought into contact with the upper and lower electrodes of the SPS sintering machine. During the sintering process, the pressure was set to 4 kN, and the temperature was increased from room temperature to 1100℃ at a rate of 5℃ / min, and held for 30 min. After sintering, the sintered body was removed from the mold, and the sintered rod was machined into a cylinder with a length of 180 mm and a diameter of 30 mm, with an M25 thread at one end. The surface runout of the cylinder did not exceed 0.03 mm.

[0058] 3) Pre-preparation of Mo-Cu composite powder

[0059] Connect the threaded end of the pre-alloyed rod to the PREP spindle, then start the vacuum system to evacuate the atomization chamber. After evacuation, fill the atomization chamber with high-purity argon gas. Once the pressure in the atomization chamber reaches 0.06 MPa, open the oxygen content analysis valve. When the oxygen content analyzer reading is <100 ppm, start the spindle and gradually increase the speed to 40,000 rpm. Start the electric arc with an input power of 700 A. After powder preparation is complete, cool for 30 minutes and open the powder hopper to collect the powder.

[0060] 4) Preparation of Mo-Cu composite materials

[0061] The alloy powder prepared in step 3) was placed into a graphite mold, and the sintering test in step 2) and the powder preparation test in step 3) were repeated. The prepared alloy material was then machined into a cylinder. The machined cylinder was then used to prepare molybdenum-copper composite powder by the PREP method.

Claims

1. A method for preparing Mo-Cu alloy powder, characterized in that, Molybdenum powder and copper powder are mixed and deoxidized, and then pre-alloyed rods are produced by spark plasma sintering. The pre-alloyed rods are then powdered by plasma rotating electrode atomization, specifically including the following steps: 1) Pretreatment of copper powder and molybdenum powder Molybdenum powder and copper powder with a particle size of less than 50μm are selected and mixed evenly in a powder mixer. The mixed powder is then treated with a hydrogen atmosphere at a temperature of 800~1050℃ to remove oxygen. 2) Preparation of Mo-Cu pre-alloying Mo-Cu pre-alloying is completed by spark plasma sintering. The oxygen-de-oxidized mixed powder is filled into a graphite mold, the graphite mold is sealed, and then both ends of the graphite mold are brought into contact with the upper and lower electrodes of the spark plasma sintering machine. The set pressure of the spark plasma sintering machine is not higher than 5kN, the set sintering temperature is 1080~1150℃, and the holding time is 30±5min. After sintering is completed, the sintered body is taken out from the graphite mold and processed into a cylinder with a length of 150~180mm and a diameter of 30mm, and a thread is processed on one end to obtain a pre-alloyed rod. 3) Pre-preparation of Mo-Cu composite powder Connect the threaded end of the pre-alloyed rod to the spindle of the plasma rotating electrode atomizing device. Then, evacuate the atomizing chamber of the plasma rotating electrode atomizing device and fill it with high-purity argon gas. When the pressure in the atomizing chamber is 0.06~0.1MPa and the oxygen content in the atomizing chamber is <100ppm, start the spindle to increase the speed and start the arc current. After the powder making is completed, cool for 30±5min and open the powder hopper to collect the powder. 4) Preparation of Mo-Cu composite materials The powder prepared in step 3) is placed in a spark plasma sintering machine, and step 2) is repeated to obtain a pre-alloyed rod. The pre-alloyed rod is then prepared into molybdenum-copper composite powder using the method in step 3). The Mo-Cu alloy powder has a D50 of less than 50 μm, an oxygen content of less than 100 ppm, and a copper weight content of less than 50%.

2. The method for preparing Mo-Cu alloy powder according to claim 1, characterized in that, Step 2) The graphite mold is a cylindrical structure. After the oxygen-deoxygenated mixed powder is placed inside the graphite mold, graphite cylinders are placed at both ends of the graphite mold to seal it.

3. The method for preparing Mo-Cu alloy powder according to claim 1, characterized in that, The surface runout of the sintered body along the circumferential direction of the cylinder in step 2) shall not exceed 0.03 mm.

4. The method for preparing Mo-Cu alloy powder according to claim 1, characterized in that, Step 3) The spindle speed of the plasma rotating electrode atomization device is 20,000~40,000 rpa / min, and the current is 500~700A.

5. The method for preparing Mo-Cu alloy powder according to claim 1, characterized in that, The operation in step 4) is performed more than twice.

6. The method for preparing Mo-Cu alloy powder according to claim 1, characterized in that, The roughness of the pre-alloyed rod described in step 2) is not higher than 0.03 mm.