Preparation method of high-temperature co-fired dissimilar metal powder with controllable shrinkage rate

Abstract

The invention relates to the technical field of metal powder preparation, in particular to a preparation method of high-temperature co-fired dissimilar metal powder with a controllable shrinkage rate. According to the technical scheme, the preparation method comprises the following steps: preparing a W and Re salt solution by a liquid-liquid method, dissolving ammonium metatungstate and ammonium perrhenate in deionized water in proportion, adding oxalic acid as a cosolvent, and reacting under heating, stirring and ultrasonic conditions to obtain a clarified W and Re salt solution; and carrying out spray drying dehydration, namely atomizing and drying the W and Re salt solution through a centrifugal spray dryer to obtain W-Re alloy precursor powder. By regulating and controlling the morphology structure of the W-Re alloy powder, on the premise that foreign impurities are not introduced, effective matching of the W-Re alloy powder and the sintering shrinkage rate of dissimilar metal is achieved, and generation of interface stress and defects is restrained; while the shrinkage behavior is adjusted, the high density and performance stability of the material are maintained, the process regulation and control mode is clear, and the repeatability is good.

Description

Technical Field

[0001] This invention relates to the field of metal powder preparation technology, and in particular to a method for preparing high-temperature co-fired dissimilar metal powders with controllable shrinkage. Background Technology

[0002] High-temperature co-fired dissimilar metal composites, especially tungsten (W)-based layered or composite structures, have irreplaceable application value in extreme environments such as key components of nuclear reactors, hot-end components of aerospace engines, and high-end medical equipment (such as CT X-ray tube rotating target disks). These materials combine tungsten with other metals (such as molybdenum (Mo) and iron (Fe)) through metallurgical bonding, aiming to integrate tungsten's high melting point, high density, excellent high-temperature strength, and radiation resistance, while simultaneously improving its room-temperature brittleness, processability, and thermophysical properties through the use of a second-phase metal.

[0003] The co-firing preparation of dissimilar metals, especially high-melting-point refractory metals, faces a fundamental technical bottleneck: the shrinkage behavior of each component during sintering differs significantly. Taking a typical W-Re alloy and Mo alloy composite system as an example, the linear shrinkage rate of commercially available W-Re alloys is typically only 0.08–0.12, while that of Mo alloys ranges from 0.16–0.20. This shrinkage mismatch generates enormous internal stress in the heterogeneous interface region during the densification stage and subsequent cooling stage of the co-firing process. This can easily lead to fatal defects such as interface cracking, interlayer delamination, or overall warping, severely restricting the fabrication of high-performance, high-reliability composite components.

[0004] Currently, industry attempts to control sintering shrinkage rate mainly focus on adjusting the sintering process (such as temperature, time, and atmosphere) or adding sintering aids. However, simply optimizing the sintering process has a limited window, making it difficult to achieve precise matching of shrinkage rates over a wide range; while introducing sintering aids may contaminate the material system, impairing the high-temperature performance, conductivity, or corrosion resistance of the composite material. Therefore, developing a method that can fundamentally control the sintering shrinkage behavior of metal powders without introducing foreign impurities is crucial for achieving high-quality co-firing of dissimilar metals. Therefore, this application proposes a method for preparing high-temperature co-firing dissimilar metal powders with controllable shrinkage rate. Summary of the Invention

[0005] The purpose of this invention is to address the shrinkage mismatch problem in the co-firing of dissimilar metals in the prior art, and to propose a method for preparing high-temperature co-fired dissimilar metal powders with controllable shrinkage rate.

[0006] The technical solution of this invention: A method for preparing high-temperature co-fired dissimilar metal powder with controllable shrinkage rate, comprising the following steps:

[0007] S1. Preparation of W and Re salt solutions by liquid-liquid method: Ammonium metatungstate (AMT) and ammonium perrhenate (NH4ReO4) are dissolved in deionized water in a certain proportion, oxalic acid is added as a co-solvent, and the reaction is carried out under heating, stirring and sonication to obtain a clear W and Re salt solution.

[0008] S2. Spray drying and dehydration: The W and Re salt solution is atomized and dried by a centrifugal spray dryer to obtain W-Re alloy precursor powder;

[0009] S3. Hydrogen reduction: The W-Re alloy precursor powder is placed in a pusher-type hydrogen reduction furnace for segmented reduction, first at low temperature and then at high temperature, to obtain spherical W-Re alloy powder.

[0010] S4. Crushing and modification: The spherical W-Re alloy powder is mixed with tungsten carbide microspheres and mechanically crushed under an inert atmosphere for 20-100 h to obtain modified W-Re alloy powder with different submicroscopic morphologies.

[0011] S5. High-temperature sintering: After the modified W-Re alloy powder is molded, it is subjected to high-temperature hydrogen sintering to obtain a W-Re alloy sintered body.

[0012] Optionally, in step S1, the amount of ammonium perrhenate added is 4%-12% of the mass of ammonium metatungstate, the amount of oxalic acid added is 12%-18% of the mass of ammonium metatungstate, the amount of deionized water added is 2.5-3.5L per kilogram of ammonium metatungstate and ammonium perrhenate, and the reaction temperature is 70-90 ℃.

[0013] Optionally, in step S2, the inlet temperature of the hot air for spray drying is 220-240 ℃, the rotation speed of the centrifugal atomizer is 350-400 r / s, and the outlet temperature is not lower than 90 ℃.

[0014] Optionally, in step S3, the reduction process is divided into a low-temperature zone and a high-temperature zone: the temperature in the low-temperature zone is 400-550 ℃, and the holding time is 0.8-1.2 h; the temperature in the high-temperature zone is 950-1100 ℃, and the holding time is 2.5-3.5 h; the thickness of the W-Re alloy precursor in the pushboat does not exceed 20 mm.

[0015] Optionally, in step S4, the crushing process is carried out under an argon atmosphere, the ball-to-material mass ratio is 10:1, the total volume of powder and grinding balls in the mixing tank does not exceed 2 / 3 of the tank's internal volume, and contact with water and alcohol solvents is avoided during the crushing process.

[0016] Optionally, in step S4, the crushing time is selected from any range of 20-25 h, 45-50 h, 70-75 h, or 95-100 h.

[0017] Optionally, in step S5, the pressing pressure is 650-750 MPa, the holding time is 1-3 min, and no molding agent is required; the sintering temperature is 2200-2400℃, and the holding time is 2.5-3.5 h.

[0018] Optionally, in step S5, the heating program for the sintering process is as follows: heating rate ≤ 6 ℃ / min below 1200 ℃, heating rate ≤ 4 ℃ / min between 1200-2000 ℃, heating rate ≤ 2 ℃ / min above 2000 ℃, and holding at 1200 ℃ for 0.8-1.2 h.

[0019] Compared with the prior art, this application includes at least one of the following beneficial technical effects:

[0020] By controlling the structure of powder, its sintering shrinkage behavior can be effectively adjusted, enabling it to achieve good shrinkage synergy with dissimilar metals with different shrinkage properties (such as molybdenum alloys), thereby suppressing the generation of interfacial stress and defects.

[0021] While adjusting the shrinkage rate, it ensures that the material can still obtain high and stable density during sintering, so that the final product maintains good mechanical and physical properties.

[0022] The method of the present invention adjusts the morphology of powder only through physical means, without adding any forming agent or sintering aid, thus avoiding the potential impact of foreign elements on the purity, high-temperature performance and conductivity of the material.

[0023] This invention can effectively control sintering shrinkage behavior by adjusting only a single process parameter. The process is simple and clear, and it is easy to achieve large-scale preparation and quality control. The powder prepared by this invention can be directly used for high-temperature co-firing of layered or composite structures such as W-Re / Mo, laying the foundation for high-reliability components required in related fields.

[0024] This invention achieves effective matching of the sintering shrinkage rate with that of dissimilar metals by controlling the morphology and structure of W-Re alloy powder without introducing foreign impurities, thereby suppressing interfacial stress and defects. While regulating shrinkage behavior, it maintains the high density and performance stability of the material, and the process control method is clear and has good repeatability. Attached Figure Description

[0025] Figure 1 This is a graph showing the changes in reduction time and temperature parameters during the precursor reduction process.

[0026] Figure 2 The image shows the powder morphology in Example 5.

[0027] Figure 3 This is a graph showing the changes in sintering time and temperature parameters during the sintering process of the alloy billet.

[0028] Figure 4 This is a dataset of density and linear shrinkage before and after sintering, as shown in the example. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0030] Example 1

[0031] Step 1: Preparation of W and Re salt solutions using liquid-liquid method

[0032] Soluble tungsten salts (ammonium metatungstate, AMT) and rhenium salts (ammonium perrhenate, NH4ReO4) were dissolved in deionized water according to their composition ratios. Oxalic acid was added to promote the dissolution of the soluble salts in the aqueous solution. The specific procedure was as follows: First, a small amount of deionized water was added to a glass chemical reactor capable of heating, sonication, and stirring. Then, predetermined amounts of AMT and NH4ReO4 were dissolved in the deionized water and added to the reactor. The reactor was then sequentially stirred, heated in an oil bath, and sonicated. When no agglomerated solids were found in the solution, the oxalic acid dissolved in the deionized water was added. After heating to a predetermined temperature, the reaction was carried out for 2 hours under stirring, oil bath heating, and sonication until the solution became clear. At this point, a liquid-liquid method solution for preparing W and Re salts was obtained.

[0033] In step one, the NH4ReO4 content is 4% of the mass of AMT, the oxalic acid content is 12% of the mass of AMT, the amount of deionized water added is 2.5 L per kilogram of AMT and NH4ReO4, and the solution temperature is 70 °C.

[0034] Step 2: Dehydrate the precursor powder obtained in Step 1.

[0035] The W and Re salt solution obtained in step one was dehydrated using a centrifugal spray dryer. The specific operation was as follows: the centrifugal spray dryer was turned on and the hot air inlet temperature was set; after the hot air inlet and outlet temperatures stabilized, the atomizing device was turned on and connected to the W and Re salt solution; the W and Re salt solution was atomized by the centrifugal atomizer and then entered the spray dryer, dried, and collected by the bottom collector, thus obtaining the W-Re alloy precursor.

[0036] In step two, the inlet temperature of the hot air is 220 ℃, the centrifugal atomizer speed is 350 r / s, and the outlet temperature of the hot air is not lower than 90 ℃.

[0037] Step 3: Reduce the dehydrated precursor powder.

[0038] A segmented pusher-type hydrogen reduction furnace was used to reduce the W-Re alloy precursor. The specific operation was as follows: the furnace temperature was raised to a predetermined temperature and hydrogen gas was introduced; the W-Re alloy precursor was loaded into the pusher to a specified thickness and fed into the reduction furnace; after reduction in the low-temperature zone for 1 hour, the precursor was transferred to the high-temperature zone for 3 hours of reduction; after the reduction time was completed, the precursor was pushed into the cooling zone, cooled to room temperature, and then removed, yielding spherical W-Re alloy powder. Figure 1 As shown, there are two temperature plateaus during the reduction process as the temperature changes over time. After the reduction time is over, the device enters the water cooling zone for further cooling.

[0039] In step three, the thickness of the W-Re alloy precursor in the pusher boat is no more than 20 mm, the reduction temperature in the low-temperature zone is 400℃, and the reduction temperature in the high-temperature zone is 950℃.

[0040] Step 4: High-temperature sintering of powder

[0041] The modified powder was sintered, and the modification effect was fed back by the changes in alloy powder, green body, and sintering performance parameters before and after sintering. The specific operation was as follows: the modified powder was pressed using a 20 mm diameter separable mold; a pressed green body was obtained after holding under pressure for 2 min; the pressed green body was then subjected to high-temperature hydrogen sintering at 2300 ℃ for 3 h; during sintering, the heating rate did not exceed 6 ℃ / min below 1200 ℃, 4 ℃ / min between 1200 ℃ and 2000 ℃, and 2 ℃ / min above 2000 ℃; after sintering, the alloy sintered body was obtained.

[0042] In step four, no forming agent is required during the powder pressing process. The powder pressing pressure is an axial pressure of 650 MPa, and the sintering process is carried out at 1200 ℃ for 1 h.

[0043] Example 2:

[0044] Step 1: Preparation of W and Re salt solutions using liquid-liquid method

[0045] Soluble tungsten salts (ammonium metatungstate, AMT) and rhenium salts (ammonium perrhenate, NH4ReO4) were dissolved in deionized water according to their composition ratios. Oxalic acid was added to promote the dissolution of the soluble salts in the aqueous solution. The specific procedure was as follows: First, a small amount of deionized water was added to a glass chemical reactor capable of heating, sonication, and stirring. Then, predetermined amounts of AMT and NH4ReO4 were dissolved in the deionized water and added to the reactor. The reactor was then sequentially stirred, heated in an oil bath, and sonicated. When no agglomerated solids were found in the solution, the oxalic acid dissolved in the deionized water was added. After heating to a predetermined temperature, the reaction was carried out for 2.2 h under stirring, oil bath heating, and sonication until the solution became clear. At this point, a liquid-liquid method solution for preparing W and Re salts was obtained.

[0046] In step one, the NH4ReO4 content is 6% of the mass of AMT, the oxalic acid content is 13% of the mass of AMT, the amount of deionized water added is 2.8 L per kilogram of AMT and NH4ReO4, and the solution temperature is 75°C.

[0047] Step 2: Dehydrate the precursor powder obtained in Step 1.

[0048] The W and Re salt solution obtained in step one was dehydrated using a centrifugal spray dryer. The specific operation was as follows: the centrifugal spray dryer was turned on and the hot air inlet temperature was set; after the hot air inlet and outlet temperatures stabilized, the atomizing device was turned on and connected to the W and Re salt solution; the W and Re salt solution was atomized by the centrifugal atomizer and then entered the spray dryer, dried, and collected by the bottom collector, thus obtaining the W-Re alloy precursor.

[0049] In step two, the inlet temperature of the hot air is 225°C, the centrifugal atomizer speed is 360 r / s, and the outlet temperature of the hot air is not lower than 90°C.

[0050] Step 3: Reduce the dehydrated precursor powder.

[0051] The W-Re alloy precursor was reduced using a segmented pusher-type hydrogen reduction furnace. The specific operation was as follows: the furnace temperature was raised to a predetermined temperature and hydrogen was introduced; the W-Re alloy precursor was loaded into the pusher according to a specified thickness and fed into the reduction furnace; after reduction in the low-temperature zone for 1 hour, the W-Re alloy precursor was transferred to the high-temperature zone for 3 hours of reduction; after the reduction time was completed, it was pushed into the cooling zone, cooled to room temperature, and then removed, yielding spherical W-Re alloy powder.

[0052] In step three, the thickness of the W-Re alloy precursor within the pusher boat is no more than 20 mm, the reduction temperature in the low-temperature region is 430℃, and the reduction temperature in the high-temperature region is 980℃.

[0053] Step 4: Crushing and modifying the tungsten-rhenium alloy powder obtained in Step 3

[0054] The spherical W-Re alloy powder prepared in step three was subjected to crushing treatment to control its submicroscopic morphology and characteristics. Specifically, the reduced powder and tungsten carbide microspheres were mixed in a mixing tank at a ratio of 10:1; the mixture was sealed in a glove box under an argon atmosphere; the mixing tank was placed in a three-dimensional powder mixer to crush the spherical W-Re alloy powder at a speed of 35 rpm; the alloy powder was crushed in the powder mixer for 21 hours; after crushing, the crushed powder was separated from the tungsten carbide microspheres using a sieve, and the obtained modified powder was stored under vacuum. Figure 2 After the alloy powder is crushed and modified, the spherical morphology in the reduced state is broken, and the powder in the modified state is distributed in a fine agglomerate.

[0055] In step four, the volume of powder and tungsten carbide pellets in the mixing tank shall not exceed 2 / 3 of the tank's volume, and contact with water and alcohol shall be avoided during the crushing process.

[0056] Step 5: High-temperature sintering of powder

[0057] The modified powder was sintered, and the modification effect was fed back by the changes in alloy powder, green body, and sintering performance parameters before and after sintering. The specific operation was as follows: the modified powder was pressed using a 20 mm diameter separable mold; a pressed green body was obtained after holding under pressure for 2 min; the pressed green body was then subjected to high-temperature hydrogen sintering at 2300 ℃ for 3 h; during sintering, the heating rate did not exceed 6 ℃ / min below 1200 ℃, 4 ℃ / min between 1200 ℃ and 2000 ℃, and 2 ℃ / min above 2000 ℃; after sintering, the alloy sintered body was obtained.

[0058] In step five, no forming agent is required during the powder pressing process. The powder pressing pressure is an axial pressure of 680 MPa, and the sintering process is carried out at 1200 ℃ for 1 h.

[0059] Example 3

[0060] Step 1: Preparation of W and Re salt solutions using liquid-liquid method

[0061] Soluble tungsten salts (ammonium metatungstate, AMT) and rhenium salts (ammonium perrhenate, NH4ReO4) were dissolved in deionized water according to their composition ratios. Oxalic acid was added to promote the dissolution of the soluble salts in the aqueous solution. The specific procedure was as follows: First, a small amount of deionized water was added to a glass chemical reactor capable of heating, sonication, and stirring. Then, predetermined amounts of AMT and NH4ReO4 were dissolved in the deionized water and added to the reactor. The reactor was then sequentially stirred, heated in an oil bath, and sonicated. When no agglomerated solids were found in the solution, the oxalic acid dissolved in the deionized water was added. After heating to a predetermined temperature, the reaction was carried out for 2.5 hours under stirring, oil bath heating, and sonication until the solution became clear. At this point, a liquid-liquid method solution for preparing W and Re salts was obtained.

[0062] In step one, the NH4ReO4 content is 8% of the mass of AMT, the oxalic acid content is 15% of the mass of AMT, and the amount of deionized water added is 3 L per kilogram of AMT and NH4ReO4. The solution temperature is 80 ℃.

[0063] Step 2: Dehydrate the precursor powder obtained in Step 1.

[0064] The W and Re salt solution obtained in step one was dehydrated using a centrifugal spray dryer. The specific operation was as follows: the centrifugal spray dryer was turned on and the hot air inlet temperature was set; after the hot air inlet and outlet temperatures stabilized, the atomizing device was turned on and connected to the W and Re salt solution; the W and Re salt solution was atomized by the centrifugal atomizer and then entered the spray dryer, dried, and collected by the bottom collector, thus obtaining the W-Re alloy precursor.

[0065] In step two, the inlet temperature of the hot air is 230 ℃, the centrifugal atomizer speed is 375 r / s, and the outlet temperature of the hot air is not lower than 90 ℃.

[0066] Step 3: Reduce the dehydrated precursor powder.

[0067] The W-Re alloy precursor was reduced using a segmented pusher-type hydrogen reduction furnace. The specific operation was as follows: the furnace temperature was raised to a predetermined temperature and hydrogen was introduced; the W-Re alloy precursor was loaded into the pusher according to a specified thickness and fed into the reduction furnace; after reduction in the low-temperature zone for 1 hour, the W-Re alloy precursor was transferred to the high-temperature zone for 3 hours of reduction; after the reduction time was completed, it was pushed into the cooling zone, cooled to room temperature, and then removed, yielding spherical W-Re alloy powder.

[0068] In step three, the thickness of the W-Re alloy precursor within the pusher boat is no more than 20 mm, the reduction temperature in the low-temperature region is 478℃, and the reduction temperature in the high-temperature region is 1020℃.

[0069] Step 4: Crushing and modifying the tungsten-rhenium alloy powder obtained in Step 3

[0070] The spherical W-Re alloy powder prepared in step three was subjected to crushing treatment to control its submicroscopic morphology and characteristics. Specifically, the reduced powder and tungsten carbide microspheres were mixed in a mixing tank at a ratio of 10:1; the mixture was sealed in a glove box under an argon atmosphere; the mixing tank was placed in a three-dimensional powder mixer to crush the spherical W-Re alloy powder at a speed of 35 rpm; the alloy powder was crushed in the powder mixer for 47 hours; after crushing, the crushed powder was separated from the tungsten carbide microspheres using a sieve, and the obtained modified powder was stored under vacuum.

[0071] In step four, the volume of powder and tungsten carbide pellets in the mixing tank shall not exceed 2 / 3 of the tank's volume, and contact with water and alcohol shall be avoided during the crushing process.

[0072] Step 5: High-temperature sintering of powder

[0073] The modified powder was sintered, and the modification effect was fed back by the changes in alloy powder, green body, and sintering performance parameters before and after sintering. The specific operation was as follows: the modified powder was pressed using a 20 mm diameter separable mold; after holding under pressure for 2 min, a pressed green body was obtained; the pressed green body was subjected to high-temperature hydrogen sintering at 2300 ℃ for 3 h; during sintering, the heating rate did not exceed 6 ℃ / min below 1200 ℃, 4 ℃ / min between 1200 ℃ and 2000 ℃, and 2 ℃ / min above 2000 ℃; after sintering, the alloy sintered body was obtained. Figure 3 During the sintering process, the temperature changes slowly over time, eventually reaching 2300 ℃. After holding at this temperature for 3 hours, the temperature is slowly lowered. This process can achieve a high density of sintered body.

[0074] In step five, no forming agent is required during the powder pressing process. The powder pressing pressure is an axial pressure of 700 MPa, and the sintering process is carried out at 1200 ℃ for 1 h.

[0075] Example 4:

[0076] Step 1: Preparation of W and Re salt solutions using liquid-liquid method

[0077] Soluble tungsten salts (ammonium metatungstate, AMT) and rhenium salts (ammonium perrhenate, NH4ReO4) were dissolved in deionized water according to their composition ratios. Oxalic acid was added to promote the dissolution of the soluble salts in the aqueous solution. The specific procedure was as follows: First, a small amount of deionized water was added to a glass chemical reactor capable of heating, sonication, and stirring. Then, predetermined amounts of AMT and NH4ReO4 were dissolved in the deionized water and added to the reactor. The reactor was then sequentially stirred, heated in an oil bath, and sonicated. When no agglomerated solids were found in the solution, the oxalic acid dissolved in the deionized water was added. After heating to a predetermined temperature, the reaction was carried out for 2.8 h under stirring, oil bath heating, and sonication until the solution became clear. At this point, a liquid-liquid method solution for preparing W and Re salts was obtained.

[0078] In step one, the NH4ReO4 content is 10% of the mass of AMT, the oxalic acid content is 17% of the mass of AMT, and the amount of deionized water added is 3.2 L per kilogram of AMT and NH4ReO4. The solution temperature is 85 ℃.

[0079] Step 2: Dehydrate the precursor powder obtained in Step 1.

[0080] The W and Re salt solution obtained in step one was dehydrated using a centrifugal spray dryer. The specific operation was as follows: the centrifugal spray dryer was turned on and the hot air inlet temperature was set; after the hot air inlet and outlet temperatures stabilized, the atomizing device was turned on and connected to the W and Re salt solution; the W and Re salt solution was atomized by the centrifugal atomizer and then entered the spray dryer, dried, and collected by the bottom collector, thus obtaining the W-Re alloy precursor.

[0081] In step two, the inlet temperature of the hot air is 235°C, the centrifugal atomizer speed is 390 r / s, and the outlet temperature of the hot air is not lower than 90°C.

[0082] Step 3: Reduce the dehydrated precursor powder.

[0083] The W-Re alloy precursor was reduced using a segmented pusher-type hydrogen reduction furnace. The specific operation was as follows: the furnace temperature was raised to a predetermined temperature and hydrogen was introduced; the W-Re alloy precursor was loaded into the pusher according to a specified thickness and fed into the reduction furnace; after reduction in the low-temperature zone for 1 hour, the W-Re alloy precursor was transferred to the high-temperature zone for 3 hours of reduction; after the reduction time was completed, it was pushed into the cooling zone, cooled to room temperature, and then removed, yielding spherical W-Re alloy powder.

[0084] In step three, the thickness of the W-Re alloy precursor within the pusher boat is no more than 20 mm, the reduction temperature in the low-temperature region is 520℃, and the reduction temperature in the high-temperature region is 1080℃.

[0085] Step 4: Crushing and modifying the tungsten-rhenium alloy powder obtained in Step 3

[0086] The spherical W-Re alloy powder prepared in step three was subjected to crushing treatment to control its submicroscopic morphology and characteristics. Specifically, the reduced powder and tungsten carbide microspheres were mixed in a mixing tank at a ratio of 10:1; the mixture was sealed in a glove box under an argon atmosphere; the mixing tank was placed in a three-dimensional powder mixer to crush the spherical W-Re alloy powder at a speed of 35 rpm; the alloy powder was crushed in the powder mixer for 74 hours; after crushing, the crushed powder was separated from the tungsten carbide microspheres using a sieve, and the obtained modified powder was stored under vacuum.

[0087] In step four, the volume of powder and tungsten carbide pellets in the mixing tank shall not exceed 2 / 3 of the tank's volume, and contact with water and alcohol shall be avoided during the crushing process.

[0088] Step 5: High-temperature sintering of powder

[0089] The modified powder was sintered, and the modification effect was fed back by the changes in alloy powder, green body, and sintering performance parameters before and after sintering. The specific operation was as follows: the modified powder was pressed using a 20 mm diameter separable mold; a pressed green body was obtained after holding under pressure for 2 min; the pressed green body was then subjected to high-temperature hydrogen sintering at 2300 ℃ for 3 h; during sintering, the heating rate did not exceed 6 ℃ / min below 1200 ℃, 4 ℃ / min between 1200 ℃ and 2000 ℃, and 2 ℃ / min above 2000 ℃; after sintering, the alloy sintered body was obtained.

[0090] In step five, no forming agent is required during the powder pressing process. The powder pressing pressure is an axial pressure of 650 MPa-750 MPa, and the sintering process is carried out at 1200 ℃ for 1 h.

[0091] Example 5:

[0092] Step 1: Preparation of W and Re salt solutions using liquid-liquid method

[0093] Soluble tungsten salts (ammonium metatungstate, AMT) and rhenium salts (ammonium perrhenate, NH4ReO4) were dissolved in deionized water according to their composition ratios. Oxalic acid was added to promote the dissolution of the soluble salts in the aqueous solution. The specific procedure was as follows: First, a small amount of deionized water was added to a glass chemical reactor capable of heating, sonication, and stirring. Then, predetermined amounts of AMT and NH4ReO4 were dissolved in the deionized water and added to the reactor. The reactor was then sequentially stirred, heated in an oil bath, and sonicated. When no agglomerated solids were found in the solution, the oxalic acid dissolved in the deionized water was added. After heating to a predetermined temperature, the reaction was carried out for 3 hours under stirring, oil bath heating, and sonication until the solution became clear. At this point, a liquid-liquid method solution for preparing W and Re salts was obtained.

[0094] In step one, the NH4ReO4 content is 12% of the mass of AMT, the oxalic acid content is 18% of the mass of AMT, the amount of deionized water added is 3.5 L per kilogram of AMT and NH4ReO4, and the solution temperature is 85 ℃.

[0095] Step 2: Dehydrate the precursor powder obtained in Step 1.

[0096] The W and Re salt solution obtained in step one was dehydrated using a centrifugal spray dryer. The specific operation was as follows: the centrifugal spray dryer was turned on and the hot air inlet temperature was set; after the hot air inlet and outlet temperatures stabilized, the atomizing device was turned on and connected to the W and Re salt solution; the W and Re salt solution was atomized by the centrifugal atomizer and then entered the spray dryer, dried, and collected by the bottom collector, thus obtaining the W-Re alloy precursor.

[0097] In step two, the inlet temperature of the hot air is 240 ℃, the centrifugal atomizer speed is 400 r / s, and the outlet temperature of the hot air is not lower than 90 ℃.

[0098] Step 3: Reduce the dehydrated precursor powder.

[0099] The W-Re alloy precursor was reduced using a segmented pusher-type hydrogen reduction furnace. The specific operation was as follows: the furnace temperature was raised to a predetermined temperature and hydrogen was introduced; the W-Re alloy precursor was loaded into the pusher according to a specified thickness and fed into the reduction furnace; after reduction in the low-temperature zone for 1 hour, the W-Re alloy precursor was transferred to the high-temperature zone for 3 hours of reduction; after the reduction time was completed, it was pushed into the cooling zone, cooled to room temperature, and then removed, yielding spherical W-Re alloy powder.

[0100] In step three, the thickness of the W-Re alloy precursor within the pusher boat is no more than 20 mm, the reduction temperature in the low-temperature zone is 550℃, and the reduction temperature in the high-temperature zone is 1100℃.

[0101] Step 4: Crushing and modifying the tungsten-rhenium alloy powder obtained in Step 3

[0102] The spherical W-Re alloy powder prepared in step three was subjected to crushing treatment to control its submicroscopic morphology and characteristics. Specifically, the following steps were performed: the reduced powder and tungsten carbide microspheres were mixed in a mixing tank at a ratio of 10:1; the mixture was sealed in a glove box under an argon atmosphere; the mixing tank was placed in a three-dimensional powder mixer to crush the spherical W-Re alloy powder at a speed of 35 rpm; the alloy powder was crushed in the powder mixer for 100 h; after crushing, the crushed powder was separated from the tungsten carbide microspheres using a sieve, and the obtained modified powder was stored under vacuum.

[0103] In step four, the volume of powder and tungsten carbide pellets in the mixing tank shall not exceed 2 / 3 of the tank's volume, and contact with water and alcohol shall be avoided during the crushing process.

[0104] Step 5: High-temperature sintering of powder

[0105] The modified powder was sintered, and the modification effect was fed back by the changes in alloy powder, green body, and sintering performance parameters before and after sintering. The specific operation was as follows: the modified powder was pressed using a 20 mm diameter separable mold; a pressed green body was obtained after holding under pressure for 2 min; the pressed green body was then subjected to high-temperature hydrogen sintering at 2300 ℃ for 3 h; during sintering, the heating rate did not exceed 6 ℃ / min below 1200 ℃, 4 ℃ / min between 1200 ℃ and 2000 ℃, and 2 ℃ / min above 2000 ℃; after sintering, the alloy sintered body was obtained.

[0106] In step five, no forming agent is required during the powder pressing process. The powder pressing pressure is an axial pressure of 750 MPa, and the sintering process is carried out at 1200 ℃ for 1 h.

[0107] like Figure 4As shown, this invention modifies spherical W-Re alloy powder prepared by a liquid-liquid method by subjecting it to different crushing times to obtain modified alloy powders with different properties. The different crushed and modified powders were then subjected to compression molding and high-temperature hydrogen sintering, resulting in Examples 1 to 5, and their density and shrinkage behavior were analyzed. The results of these examples show that with increasing crushing and modification time, the green density of the modified powder is not less than 8.9 g / cm³, the sintered green density is not less than 18.2 g / cm³, and the density fluctuation of the sintered green is less than 2.7%, exhibiting good and stable pressing and sintering properties. After modification, the linear shrinkage rate of the powder exhibits a pattern of first increasing and then decreasing. When the modification time is 70-75 h (Example 4), the linear shrinkage rate reaches a maximum of 0.212, which is higher than the shrinkage rate of commercial Mo alloys (0.16–0.20) and far higher than the shrinkage rate of commercial W alloys (0.08–0.12). When the modification time was 20-25 h (Example 2), the shrinkage rate was close to the lower limit of 0.16% for commercial Mo alloys. In the other examples, the shrinkage rate of the alloys was distributed within the range of commercial Mo alloy shrinkage rates. This invention controls the crushing effect on the spherical W-Re alloy powder by changing different crushing times, achieving a linear shrinkage rate of the sintered billet over a wide range while ensuring a high and stable sintered billet density. This solves the problem of interlayer cracking in dissimilar metal composite sintering while ensuring good sintering performance of the alloy powder.

[0108] It is worth noting that this invention, based on a deep understanding of the mechanisms influencing powder sintering behavior, prepares W-Re alloy powder with a specific spherical microstructure through liquid-liquid synthesis, spray drying, and hydrogen reduction processes. Then, its submicroscopic structure is directionally adjusted through controllable mechanical crushing. This method addresses the fundamental factor of powder physical morphology, altering the packing characteristics, surface activity, and diffusion path of the powder during pressing and sintering. This allows for systematic and continuous control of the linear shrinkage rate in the final sintering stage, forming a pure process path that regulates sintering shrinkage behavior solely through the powder's own structural design, without relying on external additives. This method effectively controls the sintering shrinkage rate of W-Re alloys, enabling it to match the sintering behavior of various dissimilar metals such as Mo alloys. It significantly reduces interfacial thermal stress during co-firing and suppresses defects such as cracking and delamination. Simultaneously, this method maintains high density and performance stability of the material while adjusting the shrinkage rate, with clear process parameters and good repeatability, providing a practical technical foundation for the reliable preparation of high-performance W-Re / Mo and other dissimilar metal composite materials.

[0109] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A method for preparing a controllable shrinkage high-temperature co-fired heterogeneous metal powder, characterized in that, The method comprises the following steps: S1, preparing a W and Re salt solution by a liquid-liquid method, dissolving ammonium metatungstate and ammonium perrhenate in deionized water in a certain proportion, adding oxalic acid as a complexing agent, and reacting under the conditions of heating, stirring and ultrasonic, to obtain a clear W and Re salt solution; S2, spray drying and dehydrating, atomizing and drying the W and Re salt solution by a centrifugal spray dryer to obtain a W-Re alloy precursor powder; S3, hydrogen reduction, placing the W-Re alloy precursor powder in a push boat type hydrogen reduction furnace for staged reduction, first low-temperature reduction, and then high-temperature reduction, to obtain a spherical shell-shaped W-Re alloy powder; S4, crushing and modification, mixing the spherical shell-shaped W-Re alloy powder with tungsten carbide pellets, and performing mechanical crushing treatment under an inert atmosphere, with a crushing time of 20-100 h, to obtain a modified W-Re alloy powder with different submicroscopic morphologies; S5, high-temperature sintering, after the modified W-Re alloy powder is formed by molding, performing high-temperature hydrogen sintering to obtain a W-Re alloy sintered body.

2. The method of claim 1, wherein the powder is a powder of a high-temperature co-fired ceramic. In step S1, the addition amount of ammonium perrhenate is 4%-12% of the mass of ammonium metatungstate, the addition amount of oxalic acid is 12%-18% of the mass of ammonium metatungstate, the addition amount of deionized water is 2.5-3.5 L per kg of ammonium metatungstate and ammonium perrhenate, and the reaction temperature is 70-90 ℃.

3. The method of claim 1, wherein the powder is a powder of a high-temperature co-fired ceramic. In step S2, the hot air inlet temperature of the spray drying is 220-240 ℃, the rotation speed of the centrifugal atomizer is 350-400 r / s, and the outlet temperature is not lower than 90 ℃.

4. The method of claim 1, wherein the powder is a powder of a high-temperature co-fired ceramic. In step S3, the reduction process is divided into a low-temperature zone and a high-temperature zone: the temperature of the low-temperature zone is 400-550 ℃, and the temperature is kept for 0.8-1.2 h; the temperature of the high-temperature zone is 950-1100 ℃, and the temperature is kept for 2.5-3.5 h; the laying thickness of the W-Re alloy precursor in the push boat is not more than 20 mm.

5. The method of claim 1, wherein the powder is a powder of a high-temperature co-fired ceramic. In step S4, the crushing treatment is performed under an argon atmosphere, the mass ratio of the balls to the powder is 10:1, and the total volume of the powder and the grinding balls in the mixing tank is not more than 2 / 3 of the tank volume.

6. The method of claim 1, wherein the powder is a powder of a high-temperature co-fired ceramic. In step S4, the crushing time is selected from any one of the ranges of 20-25 h, 45-50 h, 70-75 h or 95-100 h.

7. The method of claim 1, wherein the powder is a powder of a high-temperature co-fired ceramic. In step S5, the pressing pressure is 650-750 MPa, and the pressure holding time is 1-3 min, without adding a forming agent; the sintering temperature is 2200-2400 ℃, and the temperature is kept for 2.5-3.5 h.

8. The method of claim 7, wherein the powder is a powder of a high-temperature co-fired ceramic. In step S5, the temperature rising program of the sintering process is as follows: the temperature rising rate is ≤6 ℃ / min below 1200 ℃, the temperature rising rate is ≤4 ℃ / min between 1200 ℃ and 2000 ℃, the temperature rising rate is ≤2 ℃ / min above 2000 ℃, and the temperature is kept for 0.8-1.2 h at 1200 ℃.

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